1---An-Overview-of-the-Genus-Chlamydomonas_1989_The-Chlamydomonas-Sourcebook

Prévia do material em texto

An Overview 
of the Genus 
Chlamydomonas 
Introduction 
This chapter reviews the history of research on species of the genus 
Chlamydomonas, with emphasis on the genetically important species C. 
reinhardtii and C. eugametos. The origin of the principal laboratory 
strains of these species is given in detail (insofar as the historical records 
permit), as questions of strain identity may be important in modern 
experimental work. The chapter concludes with a brief discussion of 
other Chlamydomonas species which have received more than passing 
attention in laboratory studies. 
Description of the Genus 
The genus Chlamydomonas (Greek: chlamys, a cloak or mantle; monas, 
solitary, now used as a generic term for certain unicellular flagellates) 
was named by C. G. Ehrenberg (1833, 1838), and probably corresponds 
to the flagellate Monas described in 1786 ( O . F. Müller, cited by Gerloff, 
1940; Ettl, 1976a). The species described by Ehrenberg is uncertain; Ettl 
(1976a) believes it may have been C. pulvisculus, but since the published 
description and illustration could apply to several of the species recog-
nized today, he considers the type genus to be C. reinhardtii, which was 
not named until 1888 by Dangeard. The family Chlamydomonadaceae 
includes about 800 species in 33 genera, of which Chlamydomonas ac-
counts for by far the greatest number (Bourrelly, 1966; Jakubiec, 1984). 
A schematic view of the principal features of a Chlamydomonas cell is 
shown in Figure 1.1. 
Chlamydomonas is considered by some phycologists to include the 
genus Chloromonas, whose cells are similar in overall architecture but 
lack pyrenoids. Pascher (1927) combined these two genera in his com-
prehensive treatment of the Vol vocales, but more recent works (Gerloff, 
1962; Fott, 1974; Ettl, 1976a, 1983; Prescott, 1978) have usually sepa-
rated them. There is also argument whether Gloeomonas should be 
regarded as a separate genus, the principal distinguishing feature of this 
group being a slightly wider separation of the flagellar origins compared 
1 
1 
2 1. An Overview of the Genus Chlamydomonas 
Figure 1.1. Schematic diagram of a typical 
cell of Chlamydomonas reinhardtii. C, chlo-
roplast; E, eyespot; F, flagella; FR, site of 
flagellar roots (see Figure 3.13 for detailed 
diagram); G, Golgi; M, mitochondria; N , nu-
cleus with nucleolus; P, pyrenoid; V, vacu-
ole; W, wall. 
to those of most Chlamydomonas species (see Ettl, 1965a,c; Fott, 1974). 
Another major genus of the same family is Carteria, whose cells have 
four rather than two flagella but otherwise look very much like those of 
Chlamydomonas. A t least one "Carteria" species has been demon-
strated to be a long-lived quadriflagellate product of Chlamydomonas 
mating (Behlau, 1939; see Chapter 4) , and it is tempting to speculate that 
this may in fact be the evolutionary origin of this genus. Sphaerellopsis 
and Smithsonimonas have a wide, gelatinous sheath that differs from the 
shape of the protoplast, in contrast to Chlamydomonas and Chloro-
monas, in which the sheath, if any, conforms closely to the protoplast 
shape. Polytoma is a genus of nonphotosynthetic flagellates that closely 
resemble Chlamydomonas in body structure and appear to retain some 
vestige of chloroplast nucleic acids and ribosomes (see Pringsheim, 
1963a; Siu et al., 1976a-c). The genus Polytomella comprises another 
group of colorless species that differ from Polytoma in lacking cell walls. 
Dunaliella and related genera form an analogous group of wall-less green 
flagellates which in many respects appear very closely allied to the 
Chlamydomonadaceae. The evolutionary relationships of Chlamydo-
monas to other genera, and particularly the position of the Volvocales as 
a side branch in the development of higher plants from green algae, have 
been explored in detail by investigators in several laboratories. The 
composition and organization of the cell wall, the morphology of the 
flagellar root system, and the structures involved in cytokinesis are the 
most significant features contributing to evolutionary schemes within 
Description of the Genus 3 
the Chlorophyta (see Kochert, 1973; Pickett-Heaps, 1975; Ettl, 1981; see 
also Chapter 3 for further discussion). 
Although cell body shape and size vary among Chlamydomonas spe-
cies (Figure 1.2), the overall polar structure, with paired apical flagella 
and basal chloroplast surrounding one or more pyrenoids, is constant. 
Cells are usually free-swimming in liquid media but on solid substrata 
may be nonflagellated and are often seen in gelatinous masses similar to 
those of the algae Palmella or Gloeocystis in the order Tetrasporales. 
This condition is referred to as a "palmelloid" state (Fott and N o v -
akova, 1971). There is even some discussion that Gloeocystis may com-
prise palmelloid Chlamydomonas species for which no motile stage has 
been identified (Badour et al., 1973). The Chlamydomonas wall is dis-
tinct, with some variation in thickness among species, and some species 
secrete a mucilaginous polysaccharide coating. Most species have a 
prominent eyespot, usually red, and two or more contractile vacuoles. 
Asexual division occurs by lengthwise division of the protoplast. Usu-
ally two successive divisions occur to form four daughter cells, which 
are then released from the mother cell wall. The forms of sexual repro-
duction range from isogamy (fusion of morphologically similar gametes, 
the most prevalent form; Figure 1.3) to oogoniogamy or oogamy (forma-
tion of clearly differentiated egg and sperm cells) and are not diagnostic 
of the genus (see Chapter 4 for further discussion). For many of the 
described species, no sexual cycle has been observed. Sexual fusion of 
whatever style leads to formation of a diploid zygospore with a hard, 
thick wall, which is resistant to adverse environmental conditions. Some 
species also form asexual resting spores, or akinetes. 
Dill (1895) listed 15 species of Chlamydomonas, of which six were 
new descriptions. By 1927 the list had grown to 146 species found in 
central Europe. Pascher (1927) delineated six subgenera based on chlo-
roplast shape and number and position of the pyrenoid(s), and Gerloff 
(1940) provided a new key to these and described additional species, 
bringing the total to 321. The most recent comprehensive work on the 
genus is Ettl's (1976a) monograph, in which the literature on 459 species 
is summarized. Ettl elevates the previous subgenus Chloromonas to a 
separate genus and divides the remaining species into nine groups, 
which he prefers to call Hauptgruppen rather than subgenera, implying 
no formal taxonomic rank (Figure 1.4; Table 1.1). Apart from his assign-
ment of all snow- and ice-dwelling forms to one group (Sphaerella), Ettl 
considers neither habitat nor mode of reproduction in making these 
major divisions. Within most of the nine groups, Ettl further separates 
species with similar chloroplast morphology. Species are distinguished 
from one another by several traits, including presence or absence of a 
pronounced apical papilla, number and position of contractile vacuoles, 
overall body shape, thickness of the cell wall, shape and position of the 
eyespot, and whether a gelatinous sheath surrounds the cell. The varia-
tions in chloroplast shape within the genus, and a possible scheme for 
4 1. An Overview of the Genus Chlamydomonas 
Figure 1.2. Diversity of body shapes within the genus Chlamydomonas. ( A ) Chlamydo-
monas incerta; (B) C. biconvexa; (C) C. venusta; (D) C. penium; (E) C. diffusa; (F) C. 
basimaculata; (G) C. perpusilla; (H) C. lagenula; (I) C. lunata; (J) C. gyroides; ( K ) C. 
conica; ( L ) C. musculus; (M) C. svitaviensis; ( N ) C. lismorensis; (O) C. longeovalis\ (P) C. 
tetragama; (Q) C. chlorogonioides\ (R) C. spinifera; (S) C. citriformis; (T) C. constricta; 
(U) C. incurva; (V) C. depressa; (W) C. chlorogoniopsis;(X) C. formosissima; ( Y ) C. 
ranula; (Z) C. opulenta; ( A A ) C. bergii; (BB) C. curvicauda; (CC) C. rhinoceros; (DD) C. 
complanata, with cross-sectional view below; (EE) C. dorsoventralis; (FF) C. securis. 
From Ettl (1976a). 
Description of the Genus 5 
m t * mt+ m t - m t
-
HAPLOID PROGENY (tetrad) 
Figure 1.3. Life cycle of C. reinhardtii, showing alternative fates of mated pairs as 
meiotic zygotes and as vegetative diploid cells. See Chapter 4 for further discussion. 
Courtesy of Karen Van Winkle-Swift. 
T a b l e 1.1 T a x o n o m i c Key to the Ma jor Groups of 
Chlamydomonas S p e c i e s
9 
la. Water- or soil-dwelling species, chloroplast structure easily 
recognized 2 
lb. Snow- or ice-dwelling species, chloroplast structure more 
difficult to discern Sphaerella 
2a. Cells with only one pyrenoid 3 
2b. Cells with two or more pyrenoids 7 
3a. Chloroplast cup-shaped or derived from this form 4 
3b. Chloroplast not cup-shaped 5 
4a. Pyrenoid basal Euchlamydomonas 
4b. Pyrenoid lateral Chlamydella 
5a. Chloroplast appressed to wall on one side, pyrenoid lateral Chlorogoniella 
5b. Chloroplast tubular, with cross-bridges in which the pyre-
Chlorogoniella 
noid lies embedded (Η-shaped in longitudinal section) 6 
6a. Nucleus in lumen in front of the pyrenoid Pseudagloë 
6b. Nucleus in lumen behind the pyrenoid Agloë 
8 7a. Only two pyrenoids present 
Agloë 
8 
7b. Several to numerous pyrenoids Pleiochloris 
8a. Chloroplast cup-shaped, pyrenoids lying laterally and 
opposite Bicocca 
8b. Chloroplast tubular, with two cross-bridges, before and 
behind the nucleus, in each of which lies a pyrenoid (in 
the long axis one behind the other) Amphichloris 
α
 From Ettl (1976a). 
6 1. An Overview of the Genus Chlamydomonas 
A B C 
G H I 
Figure 1.4. Schematic representation of major groups of Chlamydomonas species. Cells 
are depicted in longitudinal section, with a papilla (not present in all species) marking the 
apical end. N , nucleus, P, pyrenoid. Groups: ( A ) Euchlamydomonas; (B) Chlamydella; (C) 
Bicocca; (D) Chlorogoniella; (E) Pseudagloë; (F) Agloë; (G) Amphichloris; (H) Pleioch-
loris; ( I ) Sphaerella. From Ettl (1976a). For a taxonomic key to the major groups of 
Chlamydomonas species, see Table 1.1. 
their evolutionary relationships, have been discussed by Faridi (1975). 
Changes of apparent species character in culture are discussed by 
Gerloff (1940) and by Zahid (1976). Lewin (1975) has some acerbic 
remarks about the state of Chlamydomonas taxonomy in general. 
About a third of the species discussed by Ettl (1976a) are available 
from one or more of the major algal culture collections (Table 1.2). Wild-
type and mutant strains of C. reinhardtii, C. eugametos, and C. moewu-
sii, the principal species used experimentally, are maintained by the 
Chlamydomonas Genetics Center at Duke (Tables 1.3 and 1.4). The 
British collection ( C C A P ) also has some mutant strains of these species, 
all of which are duplicated at Duke. A few mutants of other species have 
been isolated (see Chapter 11). 
Description of the Genus 
T a b l e 1.2 Chlamydomonas S p e c i e s He ld by Major Co l l ec t ions
8 
7 
Species Group UTEX CCAP SAG ATCC Collection site 
C. acidophila Negoro Chlorogoniella 11/96 Scotland 
C. actinochloris Deason & Bold Euchlamydomonas 965 — 1.72 — Texas 
C. aculeata Korshikov Amphichloris — — 2.79 — USA? 
C. aggregata Deason & Bold Chlorogoniella 969 — 2.72 — Texas 
C. agloeformis Pascher Pseudagloë 231 11/1 11-1 — Czechoslovakia 
C. akinetos Deason & Bold Chlamydella 967 — 3.72 — Texas 
C. angulosa Dill Euchlamydomonas 618 11/59 4.72 — Japan 
C. anticontata Schiller Euchlamydomonas — — 15.84 — Germany 
C. appendiculata Deason & Bold Chlorogoniella 970 — 5.72 — Texas 
C. applanata Pringsheim Chlorogoniella 230 11/2 6.72 — Czechoslovakia 
C. applanata Pringsheim Chlorogoniella — — 12.84 — Italy 
C. archibaldii Uhlik & Bold Agloë 1795 — 1.75 — Texas 
C. asymmetric a Korshikov Chlorogoniella 450 11/41 11-41 — Connecticut 
C. augustae Skuja Euchlamydomonas — — 5.73 — Czechoslovakia 
C. baca Ettl Chlorogoniella — 11/77 — — Czechoslovakia 
C. badensis Moewus Chlorogoniella — — 123.80 — Austria 
C. bilatus Ettl Chlorogoniella — — 7.72 — Czechoslovakia 
C. brannonii Pringsheim nom. pro v. Euchlamydomonas 229 11/3 8.72 — Wisconsin? 
C. britannica Lund Euchlamydomonas 2381 — — — Washington 
C. bullosa Butcher Euchlamydomonas — 11/83 — — England 
C. callosa Gerloff Euchlamydomonas 624 — 9.72 — Netherlands 
C. callosa Gerloff Euchlamydomonas 213 11/24 — 30581 Czechoslovakia 
C. callunae Ettl Chlorogoniella — — 68.81 — Czechoslovakia 
C. capensis Pocock Pleiochloris 1753 — — — Zimbabwe 
C. carolii Ettl Chlorogoniella — — 10.72 — Czechoslovakia 
C. chlamydogama Bold mf
+ 
Agloë 103 — 11-48a — Venezuela 
C. chlamydogama Bold rar Agloë 102 11/48b 11-48b — Venezuela 
C. chlorastera Ettl Euchlamydomonas — — 69.81 — Austria 
C. chlorococcoides Ettl & Schwarz Chlorogoniella — — 15.82 — Yugoslavia 
C. chlorostellata Flint & Ettl Euchlamydomonas — 11/93 12.72 — New Zealand 
C. coccoides Butcher Euchlamydomonas 998 11/81 — — England 
C. concinna Gerloff Chlamydella — — 16.82 — Yugoslavia 
C. cribrum Ettl Euchlamydomonas 1341 — 13.72 — Czechoslovakia 
C. cw/tews Ettl Chlorogoniella — — 17.73 — Czechoslovakia 
C. culleus Ettl Chlorogoniella — — 13.84 — Italy 
C. deasonii Ettl Pleiochloris 968 — 46.72 — Texas 
C. debaryana Goroschankin Euchlamydomonas — — 14.72 — Connecticut 
C. debaryana Goroschankin Euchlamydomonas — 1 l/56a — — Mexico 
C. debaryana Goroschankin Euchlamydomonas — 1 l/56b — — Mexico 
C. debaryana Goroschankin Euchlamydomonas 344 — — — Mexico^ 
C. debaryana Goroschankin Euchlamydomonas 407 — — — 7 
C. debaryana Goroschankin Euchlamydomonas — 11/94 — — Czechoslovakia 
C. debaryana Goroschankin var. cris-
tata Ettl Euchlamydomonas 1344 11/74 15.72 — Czechoslovakia 
C. dorsoventralis Pascher Euchlamydomonas 228 11/4 — 30594 Czechoslovakia 
[C. dysosmos Moewus: see 
C. sphagnophila var. dysosmos] 
C. elegans West Chlorogoniella — — 16.72 — France 
C. elliptica Korshikov var. britannica 
Fritsch & John mt
+ 
Chlamydella 1059 — 64.72 — Nicaragua 
C. elliptica Korshikov var. britannica 
Fritsch & John rar Chlamydella 1060 — 65.72 — Nicaragua 
C. eugametos Moewus Chlamydella (see Table 1.3) 
C. euryale Lewin Chlamydella — 11/62 — — Nova Scotia 
C. euryale Lewin Chlamydella 2274 — — — China 
C. fimbriata Ettl Euchlamydomonas 1349 11/69 17.72 — Czechoslovakia 
C. fottii King Euchlamydomonas 1908 — 21.83 — Texas 
(continued) 
1. An Overview of the Genus Chlamydomonas 
T a b l e 1.2 (continued) 
Species Group UTEX CCAP SAG ATCC Collection site 
C.foveolarum Skuja Chlamydella — 11/68 — — England 
C. frankii Pascher mt
+ 
Euchlamydomonas 1057 — 18.72 — Florida 
C. frankii Pascher rar Euchlamydomonas 1058 — 19.72 — Florida 
C. geitleri Ettl Chlorogoniella 2289 — 6.73 — Czechoslovakia 
C. gelatinosa Korshikov Euchlamydomonas — — 69.72 — Czechoslovakia 
C. gerloffii Ettl Euchlamydomonas 1348 11/72 20.72 — Czechoslovakia 
C. gigantea Dill Pleiochloris 848 — 21.72 — California 
C. globosa Snow Euchlamydomonas — — 81.72 — Netherlands 
C. gloeopara Rod he & Skuja Chlamydella 227 11/7 11-7 30586 Sweden 
C. gloeophila Skuja Chlorogoniella — — 14.84 — Yugoslavia 
C. gloeophila Skuja var. irregularis Ettl 
m/
f 
Chlorogoniella 607 — 12-4 — Indiana 
C. gloeophila Skuja var. irregularis Ettl 
m r Chlorogoniella — — 12-5 — New York 
C. gregaria Butcher Chlorogoniella — 11/84b — — Wales 
C. gymnogama Deason Chlamydella 1638 — 2.75 — Alabama 
C. #v r /« Pascher Euchlamydomonas 226 11/8 11-8 — Czechoslovakia 
C. hindakii Ettl Chlorogoniella 1338 — 22.72 — Czechoslovakia 
C. humicola Lucksch Chlorogoniella 225 11/9 11-9 30455 Czechoslovakia 
C. humicola Lucksch Chlorogoniella — — 122.80 — Germany 
C. Ayi/ra Ettl mt
+t 
Chlorogoniella 4 11/6a 11-6a 30423 Czechoslovakia 
C. hydra Ettl m/"' Chlorogoniella 5 11/6b 11-6b 30401 CzechoslovakiaC. /7>>i/ra Ettl rar' Chlorogoniella 6 11/6c 11-6c — Czechoslovakia 
C. hydra Ettl var. micropapillata Ettl Chlorogoniella — 11/76 4.73 — Czechoslovakia 
C. incerta Pascher Euchlamydomonas — — 7.73 — Cuba 
C. cf. incerta Pascher Euchlamydomonas — — 23.72 — France 
C. indie a Mitra Chlamydella 223 11/11 11-11 — India 
C. mi'pi« Ettl Euchlamydomonas 1347 11/70 11.73 — Czechoslovakia 
C. /Wp/i/ Ettl Euchlamydomonas — — 70.81 — <> 
C. inflexa Pringsheim Chlorogoniella 727 — 24.72 — Scotland 
C. intermedia Chodat Euchlamydomonas 222 11/13 11-13 30631 England 
C. intermedia Chodat var. antarctica Euchlamydomonas 1964 1 l/13h> — — Antarctica 
C. isabeliensis King Euchlamydomonas 1907 — 20.83 — Texas 
C. iyengarii Mitra Euchlamydomonas 221 11/14 25.72 — India 
C. komarekii Ettl Chlorogoniella — — 71.81 — Czechoslovakia 
C. komma Skuja Euchlamydomonas 579 11/63 26.72 — Japan 
C. laciniato-stellata nom. prov. Ettl — — 20.73 — 9 
C. / M / K / I Ï Ettl Agloë — — 17.82 — Italy 
C. macrostellata Lund Chlorogoniella — 11/109 72.81 — New Zealand 
C. macrostellata Lund var. gallica 
Bourrelly Chlorogoniella — — 12.73 — France 
C. maruanii Ettl Euchlamydomonas — — 73.81 — Germany 
C. media Klebs Chlamydella — — 74.81 — Czechoslovakia 
C. m^fl /w Bischoff & Bold Pleiochloris 1492 — 9.84 — Texas 
C. melanospora Lewin rar Chlamydella 2021 — 23.83 — California 
C. melanospora Lewin mr Chlamydella 2022 — 22.83 — California 
C. meslinii Bourrelly Euchlamydomonas — — 75.81 — France 
C. mexicana Lewin rar Agloë 729 11/55a? 11-60a — Mexico 
C. mexicana Lewin mt
+ 
Agloë 730 11/55b? 11-60b — Mexico 
C. minutissima Korshikov mt
+ 
Chlorogoniella 1055 — 27.72 — California 
C. minutissima Korshikov rar Chlorogoniella 1056 — 28.72 — California 
C. minutissima Korshikov mt
+ 
Chlorogoniella 1063 — 29.72 — California 
C. minutissima Korshikov rar Chlorogoniella 1064 — 30.72 — California 
C. moewusii Gerloff Chlamydella (see Table 1.3) 
C. monadina Stein Chlamydella 493 — 31.72 — Indiana 
C. monadina Stein Chlamydella 760 — — — Indiana 
C. monoica Strehlow Euchlamydomonas 220 — 33.72 30629 Germany 
(continued) 
8 
Description of the Genus 
T a b l e 1.2 (continued) 
9 
Species Group UTEX CCAP SAG ATCC Collection site 
C. monoica Strehlow Euchlamydomonas — 11/17 — Czechoslovakia 
C. mucicola Schmidle Chlorogoniella — — 19.82 — Yugoslavia 
C. mutabilis Gerloff Pseudagloë 578 — 34.72 — 
C. nivalis Wille Sphaerella 1969 ll /5lb — — Oregon 
C. noctigama Korshikov Chlamydella l l4 — 35.72 — England 
C. noctigama var. ellipsoidea Chlamydella — — 36.72 — Czechoslovakia 
C. oblonga Pringsheim Chlorogoniella 839 — 37.72 — Caroline Islands 
C. oblonga Pringsheim Chlorogoniella 219 11/18 — — Czechoslovakia 
C. orbicularis Pringsheim Euchlamydomonas 218 11/19 11-19 — Czechoslovakia 
C. oviformis Pringsheim Chlorogoniella 217 — 11-20 — Czechoslovakia 
C. pallens Pringsheim Chlamydella — — 11-67 — South Africa 
C. pallidostigmatica King Chlamydella I905 — 9.83 — Texas 
C. par alle striata Korshikov Euchlamydomonas — — 2.73 — 
C. parvula Gerloff Chlamydella — 11/95 — — Scotland 
C. petasus Ettl Euchlamydomonas — — 10.73 — Czechoslovakia 
C. peterfii Gerloff Chlamydella 728 — 38.72 — Canada, North-
west Terr. 
C. peterfii Gerloff Chlamydella — — 70.72 — Czechoslovakia 
C. peterfii Gerloff Chlamydella 2400 — — — California 
C. philotes Lewin Agloë 2024 11/53 11-53 — Mexico 
C. pila Ettl Euchlamydomonas — — 39.72 — Czechoslovakia 
C. pinicola Ettl Chlorogoniella 1339 — 40.72 — Czechoslovakia 
C. pitschmannii Ettl Chlorogoniella — — 14.73 — Czechoslovakia 
C. planoconvexa Lund Chlamydella — — 18.82 — Italy 
C. plethora Butcher Chlorogoniella — 11/84a — — England 
C. plethora Butcher Chlorogoniella — 11/86a — — England 
C. plethora Butcher Chlorogoniella — 11/86b — — England 
C. proboscigera Korshikov var. con-
ferta Euchlamydomonas 451 — 11.72 — Connecticut 
C. proteus Pringsheim Chlorogoniella 216 U/21 41.72 30452 Czechoslovakia 
C. pseudagloë Pascher Agloë 405 1 l/22b — 13020 Connecticut 
C. pseudagloë Pascher Agloë — — — 12235 •> 
C. pseudococcum Lucksch Chlorogoniella 214 11/23 11-23 30451 Czechoslovakia 
C. pseudogigantea Korshikov Pleiochloris 943 — 72.72 — Austria 
C. pseudogigantea Korshikov, cogwheel 
strain Heimke & Starr Pleiochloris 2215 — — — Zimbabwe 
C. pseudogigantea Korshikov, long 
taper strain Heimke & Starr Pleiochloris 2216 — — — Zimbabwe 
C. pseudogigantea Korshikov, trifurcate 
strain Heimke & Starr Pleiochloris 2217 — — — Zimbabwe 
C. pseudogloeogama Gerloff Chlamydella — — 15.73 — Czechoslovakia 
C. pseudomacrostigma Peterfi Euchlamydomonas — 11/82 — — England 
C. pseudomicrosphaera King Euchlamydomonas 1906 — 24.83 — Texas 
C. pseudopertusa Ettl Amphichloris — — 42.72 — Czechoslovakia 
[C. pulchra Pringsheim: see C. callosa] 
C. Pulsatilla Wollenweber Euchlamydomonas 410 11/44 44.72 — Finland 
C. Pulsatilla Wollenweber Euchlamydomonas — 11/105 — — Scotland 
C. pulvinata Vischer Chlamydella 212 11/25 45.72 — Switzerland 
C. pumilio Ettl Chlorogoniella — — 18.73 — Czechoslovakia 
[C. pyrenoidosa Deason & Bold: see C. 
deasonii] 
C. radiata Deason & Bold Agloë 966 — 47.72 — Texas 
C. rapa Ettl Chlorogoniella 1342 — 48.72 — Czechoslovakia 
C. rapa f. vast a Ettl Chlorogoniella — 11/73 — — Czechoslovakia 
C. raudensis Ettl Chlorogoniella — — 49.72 — Czechoslovakia 
C. reginae Ettl & Green Euchlamydomonas — 11/78 — — France 
C. reinhardtii Dangeard Euchlamydomonas (see Table 1.4) 
(continued) 
10 1. An Overview of the Genus Chlamydomonas 
Species Group UTEX CCAP SAG ATCC Collection site 
C. reisiglii Ettl Chlorogoniella 11/104 England 
C. rima Flint & Ettl Chlorogoniella — — 50.72 — New Zealand 
C. äff. rotula Playfair Agloë — 11/33 11-33 30449 Switzerland 
C. sajao Lewin nom. pro v. Pseudagloë 2277 — — — China 
C. segnis Ettl Euchlamydomonas 1343 11/71 52.72 — Czechoslovakia 
C. segnis Ettl Euchlamydomonas 1919 — 1.79 — Manitoba 
C. simplex Pascher Euchlamydomonas — — 13.79 — 9 
C. smithii Hoshaw & Ettl Euchlamydomonas (see Table 1.4) 
C. sphaerella Pringsheim nom. pro v. Sphaerella 210 11/27 55.72 — England 
C. sphaeroides Gerloff Euchlamydomonas — — 4.83 — Algeria 
C. sphaeroides Gerloff Euchlamydomonas 208 11/29 58.72 — Czechoslovakia 
C. sphagnophila Pascher Chlamydella 293 — 56.72 — Scotland 
C. sphagnophila Pascher var. dysosmos 
(Moewus) Ettl Chlamydella — 11/31 — 30450 Canada, province 
unknown 
C. sphagnophila Pascher var. dysosmos 
(Moewus) Ettl Chlamydella — 11/36a 11-36a — New York 
C. spreta Butcher Chlorogoniella — 11/87 — — England 
C. starrii Ettl Chlorogoniella — — 3.73 — Czechoslovakia 
C. stercoraria Pringsheim nom. pro v. 466 11/49 11-49 — England 
C. subangulosa Fritsch & John Euchlamydomonas 209 11/28 57.72 — England 
C. subehrenbergii Butcher Euchlamydomonas — 11/88 — — England 
C. subtilis Pringsheim Chlorogoniella — — 78.81 — Hungary 
C. subtilis Pringsheim Chlorogoniella 207 11/30 — — Czechoslovakia 
C. surtseyensis Uhlik & Bold Chlamydella 1796 — 3.75 — Iceland 
C. terricola Gerloff Chlamydella 406 — 59.72 — Connecticut 
C. terricola Gerloff Chlamydella — — 8.73 — Czechoslovakia 
C. texensis King Chlorogoniella 1904 — 10.83 — Texas 
C. transita Ettl Chlorogoniella 1345 — — — Czechoslovakia 
C. typhlos Gerloff Chlamydella — — 2.83 — Germany? 
C. typica Deason & Bold Euchlamydomonas 971 — 61.72 — Texas 
C. ulvaensis Lewin Chlamydella 724 11/58 62.72 — Scotland 
C. uva-maris Butcher Euchlamydomonas — 11/89 — — England 
C. vectensis Butcher Chlamydella — 11/90 — — England 
C. yellow stone nsis Ko\
J 
Sphaerella 1970 — 29.83 — Oregon 
C. zimbabwiensis Heimke & Starr male Pleiochloris 2212 — — — Zimbabwe 
C. zimbabwiensis Heimke & Starr 
female Pleiochloris 2213 — — — Zimbabwe 
C. zimbabwiensis Heimke & Starr 
homothallic Pleiochloris 2214 — — — Zimbabwe 
" Schematic drawings of groups are shown in Figure 1.4. Abbreviations: UTEX, University of Texas Algal Collection, Austin; 
CCAP, Culture Centre of Algae and Protozoa, Ambleside; SAG, Sammlungvon Algenkulturen, Göttingen; ATCC, American 
Type Culture Collection, Rockville. Complete addresses and telephone numbers can be found in Chapter 12. 
b
 The SAG catalogue indicates that their 14.72 is equivalent to UTEX 344; however, UTEX lists the isolation site of 344 as 
Mexico, suggesting that it may instead be equivalent to one of the CCAP strains. 
c
 Listed by SAG as C. eugametos "subdioecious," and by ATCC as C. eugametos isolated by Czurda from contaminated 
cultures obtained from Moewus. See Farooqui (1974). 
d
 May be a Chloromonas species rather than Chlamydomonas; appears to lack pyrenoids (G. J. Morris, personal communica-
tion). 
T a b l e 1.2 (continued) 
Description of the Genus 11 
T a b l e 1.3 I so la tes of the C. eugametos-C. moewusii Group 
in Ma jor S tock C o l l e c t i o n s
3 
Isolate UTEX CCAP SAG ATCC CGC Origin 
C. eugametos mt
+ 
ll/5a 11-5a — — Germany, Moewus/Czurda 
C. eugametos mt~ — ll/5b — — — Germany, Moewus/Czurda 
C. eugametos mt
+ — ll/5c 11-5 c — — Germany, Moewus 
C. eugametos mt~ — ll/5d 11-5d — — Germany, Moewus 
C. eugametos mt
+ 
9 — — — CC-1419 Germany, Moewus 
C. eugametos mt~ 10 — — — CC-1420 Germany, Moewus 
C. moewusii mt 97 ll/16f ll-16f 30588 CC-55 New York, Provasoli 
C. moewusii mt~ 96 ll/16g ll-16g 30418 CC-56 New York, Provasoli 
C. moewusii yapensis mt
+ 
792 ll/61a — — CC-1897 Caroline Islands, Lewin 
C. moewusii yapensis mt 793 ll/61b — — — Caroline Islands, Lewin 
C. moewusii mt
+
 Toyonaka 
strain 2019 — — — CC-1903 Japan, Majima & Iwasa 
C. moewusii mt~ Toyonaka 
strain 2018 — — — CC-1902 Japan, Majima & Iwasa 
C. moewusii var. 
microstigmata mt
+ 
1053 11/108 81.81 — CC-1900 Iowa, Smith 
C. moewusii var. 
microstigmata mt~ 1054 11/108 82.81 — CC-1901 Iowa, Smith 
C. moewusii var. monoica 
(homothallic) 2020 — — — CC-1904 Alabama, Ratnasabapathy 
C. moewusii var. rotunda 
mt 576 11/64a ll-61a — CC-1887 Japan, Tsubo 
C. moewusii var. rotunda 
mt 577 ll/64b ll-61b — CC-1888 Japan, Tsubo 
C. moewusii var. tenuichloris 
mt 1033 — — — CC-1898 Japan, Tsubo 
C. moewusii var. tenuichloris 
mt 1034 — — — CC-1899 Japan, Tsubo 
a
 Abbreviations as in Table 1.2; CGC, Chlamydomonas Genetics Center, Duke University. Mutant strains of these species are 
also held by the Chlamydomonas Genetics Center and U T E X collections (see Chapter 12). This group of species comprises at least 
five sexually incompatible syngens, and mating type designation has in some cases been arbitrary. The mating types given here are 
as specified by Cain (1979) and by Wiese et al. (1983). This problem is discussed at length in Chapter 4. 
The genus is of worldwide distribution and is found in a diversity of 
habitats. Although most of the described species were collected in cen-
tral Europe, this bias undoubtedly reflects the distribution of phycolo-
gists, not of Chlamydomonads. Collection sites include both temperate 
and tropical areas; a few arctic and alpine species have also been found. 
Chlamydomonas species have been isolated from freshwater ponds and 
lakes, sewage ponds, marine and brackish waters, snow, garden and 
agricultural soil, forests, deserts, peat bogs, damp walls, sap on a 
wounded elm tree, an artificial pond on a volcanic island, mattress dust 
in the Netherlands, roof tiles in India, and a Nicaraguan hog wallow. A 
petri plate exposed for 1 minute from an airplane flying at 1100 meters 
altitude produced Chlamydomonas among other algae (Brown et al., 
12 1. An Overview of the Genus Chlamydomonas 
Isolate UTEX CCAP SAG ATCC CGC Origin 
C. reinhardtii mt
+ 
90 11/32a ll-32b CC-1010 ", Massachusetts, Smith 
C. reinhardtii mt' 89 1 l/32b ll-32a — CC-1009 Massachusetts, Smith 
C. reinhardtii mt
+h 
2244 ll/32c (5.75) — CC-125 ", Massachusetts, Smith: Ebersold-
Levine strain 
C. reinhardtii mt'
 h 
2243 11/3 2d (6.75) — CC-124 ", Massachusetts, Smith: Ebersold-
Levine strain 
C. reinhardtii mt
+ 
2246 — — — CC-1690 Massachusetts, Smith; Sager 21 gr 
C. reinhardtii mt'
 h 
2247 — — — CC-1093 Massachusetts, Smith; Sager 
C. reinhardtii y-1 mt~ — — — — CC-1691 Massachusetts, Smith; Sager 6145 
C. reinhardtii mt
+ — — 73.72 — CC-407 Tokyo C8, orig. Sager 
C. reinhardtii mt~ — — — — CC-408 Tokyo C9, orig. Sager 
C. reinhardtii mt~ — — 11-32c — CC-410 Caroline Islands, Lewin 
C. reinhardtii mt? — — 77.81 — CC-1374 France, G. Paris 
C. reinhardtii mt~ — — 18.79 — CC-1418 Florida, Provasoli 
C. reinhardtii [?] — — — 18798 CC-1266 Japan, Nishimura 
C. smithii mt
+ 
1062 — 54.72 — CC-1373 Massachusetts, Smith 
C. smithii mt' 1061 — 53.72 — CC-1379 California, Smith 
C. sp. mr — — — — CC-1952 Minnesota, Gross and Lefebvre 
" "137c" strains, from G. M. Smith, reportedly collected from a potato field in Amherst, M A , December, 1945. These are the 
principal laboratory strains, of which three distinct lines are in current use. See Figure 1.5 and text for discussion. SAG no longer 
lists 5.75 and 6.75 in their catalogue, but these listings are included for historical reasons. 
h
 Cannot utilize nitrate. 
1964). Symbiotic species have been found associated with foraminifera 
(C. hedleyi and C. provasolii, J. J. Lee et al., 1974; L e e and McEnery, 
1983). 
Chlamydomonas Genetics: 1830-1960 
Descriptive studies in the nineteenth century led to comprehension of 
the life cycle of Chlamydomonas and to its early recognition as an organ-
ism with possibilities for genetic analysis. Sexual reproduction was first 
described by Goroschankin in 1875 and further studied by Reinhardt, 
Dangeard, Schmidle, Dill, and Klebs in the period 1876-1900 (see Ettl, 
1976a). Desroche (1912) in a remarkable monograph extolled the virtues 
of Chlamydomonas for studies of motility and response to light, temper-
ature, compression and gravity, but it was many years before much 
further work was done in these areas. Pascher (1918) reported segrega-
tion of genetic differences in crosses of two Chlamydomonas strains 
differing in several morphological characteristics. Although the identi-
ties of the species used by Pascher are uncertain, it is noteworthy that 
the traits in which they differed included body shape, thickness of the 
cell wall, presence or absence of the apical papilla, lateral versus basal 
position of the chloroplast, and shape of the eyespot, all of which are 
used as criteria separating species. The chloroplast position is in fact the 
principal criterion defining Ettl's Hauptgruppen (see Figure 1.4 and Ta-
ble 1.1). Since Pascher actually observed mating in progress, including 
T a b l e 1.4 Wi ld -Type Iso la tes of C. reinhardtii a n d C. smithii in Major Col lect ions 
Chlamydomonas Genetics: 1830-1960 13 
nuclear fusion, and obtained recombinant progeny, one suspects that the 
genetic distances between some species are not nearly so great as the 
taxonomic keys suggest. Similarities and differences among species with 
respect to cell wall lysis and chloroplast D N A will be discussed in Chap-
ters 3 and 8, respectively. Pascher apparently did not pursue these ge-
netic studies, although he continued to work with Chlamydomonas and 
described several new species. Kater (1929) published an extensive cy-
tological study, including descriptions of mitosis and the flagellar appa-
ratus, in Chlamydomonas nasuta, and Strehlow (1929) described mating 
in a homothallic species, C. monoica, and in certain heterothallic algae 
which are now considered to be Chloromonas species, but neither of 
these investigators carried out any genetic analysis. 
Chlamydomonas gained prominence, and eventually notoriety, with 
the publications of Franz Moewus on relative sexuality, Dauermodifika-
tionen, mating substances, and other topics. These studies were impor-
tant insofar as they demonstrated the potential utility of Chlamydo-
monas for genetic analysis. However , as Lewin (1976) says, Moewus 
"seems to have strayed from the path of strict veracity," and his experi-
mental worktherefore will not be discussed in detail here. The reader is 
referred instead to Gowans' excellent summary of Moewus's reports 
(Gowans, 1976b), to Sapp's recent essay on Moewus (Sapp, 1987), and 
to other papers that evaluate particular aspects of Moewus's data (Pa-
tau, 1941; Smith, 1946; Sonneborn, 1951; Raper, 1952; Ryan, 1955; Ren-
ner, 1958). 
Although Moewus's publications dominated the Chlamydomonas lit-
erature in the 1930s, by the next decade his reports were being chal-
lenged, and investigations were under way in other laboratories that 
would lay the foundations for the great progress made in Chlamydo-
monas genetics and cell biology in later years. Apart from Moewus 's 
work, the first attempts to preserve sexually competent strains in culture 
and to investigate the physiological basis of sexuality in Chlamydo-
monas were made by G. M . Smith, Luigi Provasoli, and Ralph Lewin in 
the 1940s (Smith, 1946, 1950; Lewin, 1949; Smith and Regnery, 1950). 
By seeking zygospores rather than vegetative cells in natural material, 
and then germinating these, Smith was able to obtain mating pairs of 15 
heterothallic strains. These included pairs of C. minutissima, C. inter-
media, C. frankii, C. elliptica var. britannica, and C. reinhardtii which 
are now maintained in the U T E X and other collections (see Tables 1.2, 
1.4). Homothallic strains were also identified. In contrast to Moewus's 
reports, Smith found that all the strains tested were capable of gameto-
genesis and mating in darkness and was unable to detect the sexual 
substances (crocetins) described by Moewus. Provasoli isolated a pair of 
C. moewusii strains which were subsequently used by Lewin for induc-
tion of mutations and further studies in genetics. These were first de-
scribed in an abstract (Lewin , 1949) prophetically entitled, "Genetics of 
Chlamydomonas—paving the w a y . " 
Apart from Pascher's early observations, which were not followed up, 
14 1. An Overview of the Genus Chlamydomonas 
and Moewus 's dubious results, no systematic isolation and analysis of 
mutants had been done on any Chlamydomonas species prior to about 
1950. R . A . Lewin (1949-1954; see 1953a paper for summary) published 
a series of papers on the genetics of C. moewusii, with paralyzed, vita-
min-requiring, and several other phenotypes being used as markers. 
Linkage was found between two pairs of loci. C. S. Gowans (1960) 
extended genetic analysis with auxotrophic and other mutants of C. 
eugametos and determined many gene-centromere distances but was 
unable to construct a complete linkage map. Although work with these 
species continues in several laboratories, C. reinhardtii has become the 
species of choice for genetic analysis, largely as a result of early work by 
Ruth Sager, Bill Ebersold, and Paul Levine . 
Wishing to study maternal inheritance, Sager was advised by C. B. 
van Nie l , in consideration of Smith's work, to use C. reinhardtii because 
its life cycle was known and it would grow in the dark on an organic 
carbon source, whereas C. eugametos and C. moewusii, at that time the 
better-known species, would not. Sager's early studies on the control of 
the sexual cycle by nitrogen availability in C. reinhardtii (Sager and 
Granick, 1953, 1954) and on pigment-deficient and antibiotic-resistant 
mutants (Sager and Palade, 1954; Sager, 1955) began a long series of 
papers. The discovery of non-Mendelian (uniparental) inheritance of 
certain antibiotic resistance mutations (Sager, 1954) opened the field of 
experimental organelle genetics, for which Chlamydomonas has re-
mained one of the best model systems. Contemporary studies by Eber-
sold, Levine , and their collaborators (Ebersold and Levine , 1959; Eber-
sold et al., 1962) led to construction of the first nuclear genetic maps for 
C. reinhardtii and to the use of Chlamydomonas mutants for diverse 
studies in cell biology, plant physiology, and other disciplines. Al l these 
topics will be discussed at length in the chapters which follow. For a 
brief review of the entire body of experimental work using Chlamydo-
monas as a model system, the article by Trainor and Cain (1986) is also 
recommended. 
Origins of the Major Laboratory Strains of Chlamydomonas 
Chlamydomonas moewusii and Chlamydomonas eugametos 
Moewus's studies were conducted primarily on a group of 16 natural and 
10 derived strains assigned to the species C. eugametos, which he de-
scribed in 1931, and on isolates of several additional species that he 
found to be interfertile with these, although by the usual taxonomic 
criteria they would appear to be widely separated (Smith, 1946). Isolates 
obtained from Moewus and supposedly equivalent to his type species of 
C. eugametos were found by Czurda (1935) and Gerloff (1940) to differ 
significantly from Moewus's description, and Gerloff redescribed one o f 
these isolates as the new species C. moewusii (see Gowans, 1963, 
1976a). The species described by Moewus resembles C. sphagnophila 
Origins of the Major Laboratory Strains of Chlamydomonas 15 
Pascher (Ettl, 1976a). Gowans (1963) suggested that the name C. euga-
metos Moewus be retained for the laboratory strains now in use, even 
though they do not conform to the description given by Moewus in 1931. 
The name of the C. moewusii strains would then become C. eugametos 
var. moewusii (Gerloff) Gowans. After comparison of the " C . eugame-
tos" strains in the Cambridge collection, Farooqui (1974) suggested that 
Moewus had used the same species name for two distinctly different 
isolates, one ( C C A P 11/5) corresponding to Czurda's emendation of 
Moewus ' original description of C. eugametos, and the other ( C C A P 
11/6) resembling C. hydra Ettl (Ettl, 1965b; see Table 1.3). Farooqui 
recommended that C. eugametos sensa Czurda be retained as a valid 
species name to include both the C C A P 11/5 series of C. eugametos and 
the laboratory strains of C. moewusii. Ettl (1976a) has preferred to desig-
nate all these strains as C. moewusii Gerloff, thereby discarding C. 
eugametos as a species name. Common laboratory usage among nontax-
onomists is to use the name C. eugametos for the strains obtained from 
Moewus and C. moewusii for all subsequent isolates, and this terminol-
ogy will be followed in the present book. Where both sets of strains have 
been used interchangeably, I will refer to the group as C. moewusii, on 
Ettl's recommendation. 
Early work by Gowans (prior to 1954 for mt
+
 and prior to 1959 for 
mt~) was done with C. eugametos strains obtained from Moewus by 
Smith, but when these stocks were lost in a culture chamber failure 
Gowans continued his work with the U T E X stocks 9 and 10, obtained 
from Moewus by Bold in 1951 (R . Starr, personal communication, cited 
in Cain, 1979). Most of Gowans's mutants were isolated in this back-
ground (Gowans, 1976a; see Chapter 11). Gerloff s type material for C. 
moewusii appears to have been lost, and the laboratory cultures of this 
species now in use ( U T E X 96 and 97, Table 1.3) are those isolated in 
N e w York by Provasoli in 1948 (see Lewin , 1949). Mutants isolated by 
Lewin (1949-1954 references) are in this background. Morphologically, 
these two strains are generally considered to be indistinguishable from 
the C. eugametos strains ( C C A P 11/5 a - c ) obtained from Moewus. The 
U T E X stocks 9 and 10 are interfertile with stocks 96 and 97, albeit with 
high lethality among meiotic products in some combinations (Gowans, 
1963; Cain, 1979; Lemieux et al., 1981). (See Chapter 4 for a discussion 
of mating type assignment in these strains.) The C. eugametos isolates 
( U T E X 9 and 10) are now known to differ from C. moewusii ( U T E X 96 
and 97) at the molecular level in restriction digests of chloroplast D N A 
(Mets , 1980; Lemieux et al., 1981; see Chapter 8) , and some physiologi-
cal and isozymic differences have also beenreported (Bernstein and 
Jahn, 1955; Trainor, 1959; Thomas and Delcarpio, 1971). Based on Im-
munoelectrophoresis of acetone extracts of whole cells, Brown and 
Walne (1967) reported that the U T E X isolates of C. eugametos and C. 
moewusii were antigenically very similar, but that C. moewusii var. 
tenuichloris and var. rotunda (see Wiese et al., 1983; Tsubo, 1961) 
16 1. An Overview of the Genus Chlamydomonas 
showed greater differences from C. moewusii than did C. eugametos. 
Although these studies were primitive by modern standards of immunol-
ogy, they are consistent with the interfertility of C. eugametos and C. 
moewusii and the inability of var. tenuichloris and var. rotunda to cross 
with either of these. Other related strains, also not interfertile, include 
C. moewusii yapensis (formerly C. moewusii syngen I I ; see Wiese et al., 
1983); C. moewusii var. monoica, a homothallic variety described by 
Deason and Ratnasabapathy (1976); and C. moewusii forma micro-
stigmata, which differs from the original C. moewusii in its small, linear 
eyespot and irregularly perforated chromatophore (Flint and Ettl, 1966). 
Chlamydomonas reinhardi, reinhardii, reinhardti, or reinhardtii? 
The species C. reinhardtii was described in 1888 by P. A . Dangeard, and 
named for Ludwig Reinhard(t), a Ukrainian botanist who in 1876 had 
published a description of copulation in a species he identified as C. 
pulvisculus. Since details of sexual reproduction in this species differed 
in several respects from those typical of C. pulvisculus as described by 
Goroschankin (see Ettl, 1976a), Dangeard described Reinhardts isolate 
as a new species, C. reinhardti. This name was later cited by Goro-
schankin (1891) and Gerloff (1940) as C. reinhardi and by Pascher (1927) 
as C. reinhardii. Reinhardts name appears in bibliographies (Gerloff, 
1940; Ettl, 1976a) with the t, but in an obituary (Reinhard, 1922) and in 
some reference materials as Reinhard. Whatever Reinhardts own pref-
erence for transliteration from the Cyrillic version of his name, the pres-
ence of the t in the original species description is binding for taxonomic 
purposes. The use of two z"s rather than one is dictated by rules of 
botanical Latin nomenclature: when the epithet is for the discoverer of a 
plant, the specific name is in the genitive singular; to form this when the 
name ends in a consonant, the letters // are added. Thus the correct 
spelling is reinhardtii (Ettl, 1976a). 
Three principal strains of C. reinhardtii are widely used for genetic 
and biochemical analyses (Figure 1.5). All have been identified in the 
literature as descendants of a mating pair (mt
+
 and mt~) of clones de-
rived from a single zygospore isolated in a potato field in Amherst, 
Massachusetts, in 1945 and designated by G. M . Smith as isolate 137c, 
referring to the third (c) zygote colony recovered from soil sample num-
ber 137 (see Table 1.4). In the early 1950s both Ebersold and Sager 
received cultures from Smith which were reported to be the 137c strain. 
However , the descendants of these cultures differ in several properties, 
most notably the ability to utilize nitrate as their sole nitrogen source. 
This distinction results from the presence in the Ebersold stocks of two 
unlinked nuclear gene mutations, nit-1 and nit-2, either one of which is 
sufficient to prevent nitrate utilization (see Chapter 6). These loci have 
been mapped to linkage groups I X and I I I , respectively (see Chapter 11). 
In 1955-1956 Ebersold went to Harvard to work with Levine, and his 
wild-type strain became the ancestral stock of the many nonphotosyn-
Origins of the Major Laboratory Strains of Chlamydomonas 17 
Tsubo 
1954 
Sager 
1953 
21 g rmt
+ 
4Y mf 
Tokyo 
1959 
C8 mt+ 
C9 mr 
Smith 
1945 
Hartshorne Cambridge 
1949 
loss of nitrate reductase 
\ 
Ebersold 
1955 
„ Levine 
' l956 
1950 
11/32a m t
+
-
11/32bmt" -
lndiana/Texas_ 
1953 
-89 "mt
+
" [mf ] 
' 90 "mf" [mt
+
] 
Göttingen 
11-32a "mt
+
" [mf ] 
11-32b "mf" [mt
+
] 
[mating types become 
labeled in reverse] 
. Gillham 
1968 
Chlamydomonas Genetics 
Center 1979 
CC-124 mt-
CC-125 m t
+ 
Lewin 
1956 
Togasaki - Luck - Goodenough 
R3 m t
+ 
NO mt" 
Figure 1.5. Laboratory strains of C. reinhardtii derived from the collection of G. M. 
Smith. Uncertainty remains as to whether the Sager, UTEX 89 and 90, and Ebersold-
Levine lines represent descendants of the same original isolate or independent isolations. 
thetic mutants isolated and characterized in Levine 's laboratory. All 
these mutant stocks appear to carry both the nit-1 and nit-2 mutations, 
indicating that these mutations were present very early in the history of 
the Ebersold-Levine line. Furthermore, isolates obtained from Eber-
sold by Lewin in 1956 were observed at the time to be unable to grow on 
nitrate medium (Lewin , personal communication). Thus if the Sager and 
Ebersold-Levine branches diverged from a common ancestor, the nit 
mutations must have arisen prior to 1956. The strains C8 and C9 of the 
algal collection in Tokyo (see Table 1.4) are derived from stocks sent to 
Tsubo by Sager in 1954 and are thus presumably equivalent to the Sager 
strain. 
The third 137c strain, which, like Sager's strain, can utilize nitrate, is 
derived from cultures given by Smith to Hartshorne (1953, 1955), who 
gave them to the Cambridge ( C C A P ) collection in 1950. The mt
+
 and mt~ 
isolates of this strain were designated C C A P ll/32a and ll/32b respec-
tively. In 1953 cultures of these stocks were sent from C C A P to the 
Indiana University collection of algae (now the University of Texas 
Algal Collection, U T E X ) , where they were numbered 89 and 90, with 89 
supposedly being mt
+
 and 90 being mt~. Later evidence indicates that 
U T E X 89 is in fact mt~ and U T E X 90 is mt
+
 ( I . Friedmann, personal 
communication to R. Starr, confirmed by the Chlamydomonas Genetics 
Center at Duke). A transatlantic mating type switch thus appears to have 
occurred (see Figure 1.5). The stocks ll-32b and ll-32a of the Samm-
lung von Algenkulturen, Göttingen, were obtained by Koch prior to 
1969 from Indiana ( U T E X ) , not from C C A P , and did not switch mating 
18 1. An Overview of the Genus Chlamydomonas 
types on the return voyage. Thus S A G 1 l-32b is equivalent to U T E X 90 
and to C C A P 1 l/32a and is mt
+
 with respect to the Ebersold-Levine and 
Sager strains. These differences should be borne in mind, particularly 
when reading the literature on gametogenesis and mating, in which be-
haviors and structures specific to one mating type are described. Other 
isolates of C. reinhardtii which are also clearly of independent origin 
(Florida and Caroline Islands strains, Table 1.4) mate well with the 137c 
strains and appear to resemble them in morphological and molecular 
respects. W e have been unable to persuade the French strain ( S A G 
77.81, CC-1374) to mate with either mt
+
 or mt~ cultures in our labora-
tory but have found that it otherwise resembles the rest of the C. 
reinhardtii strains. A l l these isolates are able to utilize nitrate. 
Will the Real 137c Please Stand Up? 
Both Sager and Levine were told that the strain given them by Smith 
was 137c. In 1955, Sager identified the mt
+
 and mt~ isolates of her 
strains as 137 + and 137- and described the isolation of the 21 gr line as a 
single-cell clone of 137
+
, selected for ability to grow well in the dark. 
Her 4 Y isolate was selected in the mt~ stock as a spontaneous mutant 
which was yellow in the dark. A subsequent note (Sager and Ramanis, 
1976a) states 
All stocks used in this work are descendants of a single pair of mating 
strains, 21 gr and 4Y, which are clonal isolates of the strains received from 
G. M. Smith. Smith's strains came initially from a single zygote isolated 
from nature, so we may assume our starting strains were minimally F fs 
from the same zygote, and probably progeny of additional rounds of inter-
crossing by Smith. 
Sager's stock 5065B, whose progenitor came from a cross of 21 gr x 
4 Y , has the constitution sr-500 act-1 msr-1 mt
+
 and is the ancestor of 
many of Sager's subsequent stocks (see Sager, 1962a; Sager and Ra-
manis, 1976a). Sager's stock 5177D, used as a control in several recent 
studies in her laboratory, is a streptomycin-resistant mt~ isolate first 
described in Burton et al. (1979). 
The stocks which became U T E X 89 and 90 are referred to in the 
original file cards of the C C A P simply as "from Gilbert Smith Via J. 
Hartshorne, Received July 1950," with no mention of 137c. Hartshorne 
himself (1953, 1955) thanks Smith for his "interest and advice" and 
acknowledges receipt of the cultures but gives no strain number or other 
description. The first published identification of these stocks as 137c is 
by Hoshaw (1965), who reviewed the remains of Smith's collection for 
U T E X (then the Indiana collection) after Smith's death in 1959 and 
equated the 89 and 90 cultures already in the collection with the 137c 
isolates. A t that time four stocks in Smith's collection were identified as 
C. reinhardtii: a mating pair, 137c mt
+
 and mr, from Amherst, Massa-
Origins of the Major Laboratory Strains of Chlamydomonas 19 
chusetts, 1945; 136f, from South Deerfield, Massachusetts, 1945; and 
684c, from Santa Cruz, California, 1946. A catalogue from Smith's notes 
of "Heterothallic species of Chlamydomonas on hand, 9/1/51," commu-
nicated by Robert Page to Richard Starr at Indiana in 1959, lists three 
additional numbers in a group with C. reinhardtii: 358, from Bluefields, 
Nicaragua, originally collected in 1940; 375, from May ville, Florida, 
1946; and 413, from Livermore, California, 1949. By the time these were 
given to the Indiana collection, 358 had been identified as C. elliptica 
var. britannica (now U T E X 1059 and 1060), and 375 as C. frankii (now 
U T E X 1057 and 1058) (see Hoshaw, 1965). Number 413, which had been 
a pair of stocks in 1951 but was now a single isolate and had been moved 
by Smith to a group by itself, was not further identified and appears to 
have been discarded. 
On examination of Smith's strains, Hoshaw in collaboration with Ettl 
concluded that strains 136f and 684c differed sufficiently from U T E X 89 
and 90 in body shape and chromatophore (chloroplast) structure to war-
rant description as a new species, which they named C. smithii (Hoshaw 
and Ettl, 1966). The Massachusetts (136f) strain is considered to be the 
type species. Both strains interact sexually with C. reinhardtii but differ 
from one another in the degree to which they form viable zygotes 
(Hoshaw and Ettl, 1966; Bell and Cain, 1983). They also differ both from 
C. reinhardtii and from each other in the restriction patterns of their 
chloroplast and mitochondrial D N A s (Boynton et al., 1984, 1987; Palmer 
et al., 1985). Because Hoshaw tested the C. smithii strains for mating 
with the U T E X 89 and 90 pair of C. reinhardtii, they too are listed in the 
U T E X and S A G catalogues with mating types reversed relative to the 
remainder of the wild-type strains. The 136f strain ( U T E X 1062, S A G 
54.72, CC-1373) is mt
+
 with respect to the Ebersold-Levine and Sager 
lines of 137c (see Table 1.4) and mates well with these lines, giving many 
viable progeny. The 684c strain ( U T E X 1061, S A G 53.72, CC-1379) 
agglutinates sexually with 136f and with the 137c strains as mt~ but 
rarely produces viable progeny. In matings with CC-125 (Ebersold-
Levine wild-type mû) to CC-1379, we observed incomplete fusions re-
sembling budding yeast cells or dumbbell configurations and saw no 
zygotes. 
The foregoing history does not permit one to state unequivocally 
whether the Levine , Sager, and U T E X lines of C. reinhardtii all came 
from the same zygote. I f Smith kept only one 137c pair and all three lines 
arose from it, then loss of nitrate reductase must have occurred between 
about 1952, when Sager obtained her stocks, and 1956, the earliest docu-
mentation of a C. reinhardtii strain unable to grow on nitrate. Nitrate 
reductase activity is suppressed in cultures grown on medium containing 
ammonia (see Chapter 6) , so there would have been no selective advan-
tage to nit
+
 stocks; however, spontaneous occurrence of two indepen-
dent mutations in the same stock in such a short time seems unlikely. I f 
20 1. An Overview of the Genus Chlamydomonas 
the lines arose from two or three different original isolates, however, it is 
not clear what these correspond to in Smith's catalogue. Molecular evi-
dence (Boynton et al., 1984, 1987, and unpublished results) rules out the 
C. smithii, C. frankii, and C. elliptica pairs as possibilities. The one 
unidentified strain, Smith 413, was listed with the C. reinhardtii group in 
1951, contemporary with the dispersal of the three major lines, but by 
1954 (unpublished notes from Robert Page) Smith had relegated this to a 
separate category, whereas the Levine, Sager, and U T E X lines are un-
questionably all C. reinhardtii and would presumably have been identi-
fied as such by Smith. Sagerand Tsubo (1961) made crosses involving "a 
pair of strains of the two mating types from one zygote and an unrelated 
strain of which were "isolated by Smith from other parts of the 
United States [than 137c]." Since the pair of strains from one zygote 
cannot be C. smithii, whose mt
+
 and mt~ isolates came from different 
sites, it seems possible that Smith had additional strains not included in 
those stock lists that have been preserved. One further possibility, 
which might be considered the compromise position, is that all three 
lines came from the same 137c zygote but arose from the four different 
meiotic products. In this scenario, the 137c zygote would be a natural 
ditype for the nit mutations, which could then have arisen at their leisure 
over time on the evolutionary scale. The major argument against this 
hypothesis is the fact that Smith listed only one pair of 137c isolates 
among his strains. 
Whatever the origin of the laboratory strains of C. reinhardtii, it is 
obviously of importance to identify the specific wild-type strain in which 
a given mutation has been isolated. For example, David Luck and Jona-
than Jarvik (personal communications) have independently found strain-
specific electrophoretic variants in flagellar proteins which could be 
confused with mutational alterations. In order to interpret their observa-
tions on induced mutations, both have had to make systematic compari-
sons of ancestral stocks in their collections. The Ebersold-Levine strain 
is used by Togasaki, by Goodenough, by Boynton and Gillham, and by 
workers in several other laboratories active in genetic research, and 
most of the nuclear mutations that have been mapped were isolated in 
this strain. Important exceptions include Sager's y-1, widely used both 
as a centromere marker and as a basis for studies of chloroplast develop-
ment; the cycloheximide-resistance mutation act-I; and Sager's allele of 
the methionine sulfoximine-resistance mutation msr-1. Sager's strain 
has also been used as the parent for isolation of new nitrate reductase 
mutations (Nichols and Syrett, 1978; Sosa et al., 1978). The strains C8 
and C9, which are derived from isolates sent to Tsubo by Sager in 1954, 
have been extensively used in physiological studies by Japanese investi-
gators but have not been widely used for genetics. The chloroplast mu-
tants isolated by Gillham, Boynton, and their collaborators were ob-
tained in the Ebersold-Levine strain, whereas Sager's were obtained in 
her strain. Possible effects of strain differences in crosses involving 
Origins of the Major Laboratory Strains of Chlamydomonas 21 
these mutants are discussed in Chapter 8. The U T E X strainshave not 
been important as a background for new mutations. 
Strain 2137 was isolated by Spreitzer (Ph.D. thesis, Case Western 
Reserve University, 1980) from a cross of 21 gr x Ebersold-Levine 137c 
mr. It was selected for ability to grow as single cells in minimal me-
dium, for negative phototaxis (agg-1, derived from Ebersold-Levine 
mt~) (see Chapters 5 and 11), and for green color when grown in the dark 
(a property of the 21 gr strain used by Spreitzer; both mt
+
 and mr 
isolates of the Ebersold-Levine wild type in Spreitzer's collection 
were yellow in the dark and were confirmed to carry a y-1 allele). Non-
photosynthetic and herbicide-resistant mutants have been isolated 
in this strain. Strain 2137 contains nit-1 and the wild type allele of 
nit-2. 
The C. smithii 136f mt
+
 strain (CC-1373) has recently found great 
utility as a source of restriction fragment length polymorphisms for nu-
clear (Ranum et al., 1988), chloroplast (Palmer et al., 1985), and mito-
chondrial (Boynton et al., 1987, 1988) D N A s . A n independently isolated 
mt~ strain, S-l D-2 (CC-1952), has also been valuable in this regard 
(Ranum et al., 1987; Gross et al., 1988). Whether these strains should be 
considered as separate species is debatable. Both are clearly interfertile 
with C. reinhardtii, but at the molecular level they are distinctive, and at 
least so far as chloroplast D N A is concerned they are far more different 
from the Ebersold-Levine and Sager strains of C. reinhardtii than are 
the Florida and Caroline Islands strains (Boynton et al., 1987, and un-
published; Table 1.4). 
Mentions of other strains of uncertain identity occasionally appear in 
the literature. Whereas zygotes formed from either the Sager or Eber-
sold-Levine strain can germinate into either four or eight products (see 
Chapter 4) , Tan and Hastings (1977) reported that a strain they called 
137F, which they equated with the 89-90 pair, yielded zygotes which 
could not form eight viable products, apparently because of a failure of 
D N A synthesis during the postmeiotic mitotic division. They cited 
Sueoka et al. (1967) for the origin of the strain, but this paper mentions 
only an octet strain from Levine and a strain from Sager which gives 
predominantly four products. Chiang et al. (1970) acknowledged receipt 
of 137F from Levine and distinguished this strain from the 89-90 pair, 
but in Siersma and Chiang (1971) the wild-type strains from Levine are 
identified as 137c. Bruce (1970) described 137F as a mating pair obtained 
from Levine in 1960, originally from Sager. Since clearly both the Eber-
sold-Levine and Sager strains can germinate into either four or eight 
viable products neither of these can be 137F as described by Tan and 
Hastings. Test crosses in our laboratory suggest that the 89-90 pair does 
form many inviable zygotes and may therefore be the 137F used by Tan 
and Hastings. The origin of this designation is still uncertain, however; 
no 137F appears in those of Smith's notes that were made available to 
us. 
22 1. An Overview of the Genus Chlamydomonas 
Other Chlamydomonas Species Used Experimentally 
Chlamydomonas reinhardtii is undoubtedly the species of choice for 
laboratory studies involving genetics, since by far the greatest number 
of mutations have been isolated and mapped in this species, and it has 
been the most thoroughly investigated structurally and biochemically. 
Chlamydomonas moewusii and C. eugametos continue to be used in 
several laboratories, particularly for studies of mating, in which context 
they provide a useful contrast to C. reinhardtii in several respects. The 
spectrum of mutants isolated in C. moewusii and C. eugametos is limited 
by their obligate photoautotrophy, and the map of nuclear linkage 
groups remains much less complete than for C. reinhardtii. A few other 
species have found special applications in research and deserve men-
tion here. 
Chlamydomonas nivalis is the principal organism found in red snow in 
arctic and alpine regions of the northern hemisphere (Viala, 1967; K o l , 
1968; Czygan, 1970; Thomas, 1972; Fjerdingstad, 1973; Fjerdingstad et 
al., 1974, 1978; Mosser et al., 1977; Kawecka and Drake, 1978; Ka-
wecka, 1981; Marchant, 1982). A second species, C. sanguinea, also 
appears in red snow deposits in Europe and in the southern hemisphere. 
Hardy and Curl (1972) provide a good, nontechnical description and 
color photographs of the red snow phenomenon. The red color devel-
oped by C. nivalis results from accumulation of carotenoids, identified 
by Viala (1966) as astaxanthin esters, in cytoplasmic granules around the 
cell periphery (Weiss, 1983b). Czygan (1970) reported that these pig-
ments accumulated under conditions of nitrogen deficiency, with a con-
comitant decrease in chlorophyll content. The red cells, which are non-
flagellated and are described in most publications as "resting cel ls ," can 
withstand prolonged storage at low temperature. Presumably the red 
pigmentation has an adaptive advantage in cells living in high light inten-
sities; similar pigment accumulations are seen in other algae such as 
Dunaliella species, which grow in salt lakes in desert regions (Ben-
Amotz and Avron , 1983). Lipid accumulation is also typical of algal cells 
grown at low temperature (Hoham, 1975; Weiss, 1983b). The structural 
features that enable these species to survive freezing are discussed in 
Chapter 2 in the context of efforts to preserve Chlamydomonas cells in 
frozen suspensions. "Green snow" species of Chlamydomonas are also 
known in frozen habitats with lower light intensity. C. balle niana, from 
the Antarctic, and C. yellowstonensis, described from Yellowstone 
National Park but also reported in the Caucasus, thrive and produce 
motile cells at temperatures below freezing ( K o l , 1941; Kol and Flint, 
1968). 
Species that produce large amounts of extracellular polysaccharide 
may have practical use as soil conditioners. Among these are C. mex-
icana, C. ulvaensis, and C. sajao (Lewin , 1956a, 1957a, 1977, 1983a, 
Other Chlamydomonas Species Used Experimentally 23 
1984; Barclay, 1983; Kroen and Rayburn, 1984; Metting, 1986). Chlamy-
domonas mexicana is now being grown commercially for agricultural 
purposes (Lewin , 1977, 1983a; Metting and Rayburn, 1983; Kroen, 1984; 
Kroen and Rayburn, 1984; Barclay and Lewin, 1985). The chemistry of 
the polysaccharides of these species will be discussed in Chapter 3. 
Chlamydomonas segnis has been studied primarily in one laboratory 
(Badour et al., 1973, 1977; Foo and Badour, 1977; Badour, 1981; Tan 
and Badour, 1983, 1986; Badour and Kim, 1986). It is a freshwater 
species, homothallic and anisogamous, which forms mucilaginous 
palmelloid colonies and is noteworthy for having a pigment-deficient 
eyespot and for accumulation of unusual crystalline protein bodies in the 
chloroplast (Ettl, 1965b, 1976a). The investigations of this species have 
been primarily physiological, concentrating especially on photosynthe-
sis. N o genetic analysis appears to have been done, although mating has 
been observed. 
Chlamydomonas chlamydogama is a vitamin Bi2-requiring species 
that has received a modest amount of experimental attention (Bold, 
1949a,b; Trainor, 1958, 1960, 1961). Chlamydomonas ρ aliens, a partially 
chlorophyll-deficient, acetate-requiring species, is also a natural B j 2 aux-
otroph and was proposed by Pringsheim (1962, 1963b) as an assay organ-
ism for this vitamin. Although C. snowiae was one of the earliest de-
scribed species, it has been studied only in regard to phototaxis (Mayer 
and Poljakoff-Mayber, 1959; Stahl and Mayer, 1963; Chorin-Kirsch and 
Mayer, 1964a,b). Chlamydomonas gymnogama (Deason, 1967), a 
homothallic species which sheds its cell walls early in mating, has been 
used as a source of wall material uncontaminated by cytoplasmic debris 
(Miller et al., 1974).Chlamydomonas monoica is a large homothallic 
species used by Van Winkle-Swift and colleagues (1982, 1986) to investi-
gate the genetic control of sexuality. Inheritance of chloroplast genes 
has been studied in this species, and mutants have been isolated which 
are defective in mating or in zygote formation (see Chapter 4) . Chlamy-
domonas dysosmos (now designated by Ettl, 1976a, as C. sphagnophila 
var. dysosmos) has been used for a few cytological and physiologi-
cal studies, and some mutants have been isolated (Lewin , 1954b; Nei l -
son et al., 1972; Silverberg, 1974; Silverberg and Sawa, 1984). A few 
mutant strains of C. debaryana and C. philotes have also been ob-
tained (see Chapter 11). Chlamydomonas geitleri, another homothallic 
species, has been studied intensively by Necas and colleagues (1981— 
1986c; Zârsky et al., 1985) but has not yet been exploited for genetic 
analysis. 
Physiological and ecological studies have been made of various ma-
rine species (Antia et al., 1975, 1977; Green et al., 1978; Paul and Cook-
sey, 1979; Turner, 1979; Saks, 1982; Cann and Pennick, 1982) and of 
acidophilic species (Erlbaum, 1968; Cassin, 1974; Rhodes, 1981). Sev-
eral species have been used as test organisms for pollution in natural 
24 1. An Overview of the Genus Chlamydomonas 
waters and for laboratory studies of environmental toxins (Soto et al., 
1975a-1979b; Overnell, 1975; Delcourt and Mestre, 1978; Hutchinson et 
al., 1981, 1985; Bates et al., 1982-1985; Hellebust et al., 1982; Irmer et 
al., 1986). Chlamydomonas reinhardtii has been used for most labora-
tory tests of pollutants, however (Button and Hostetter, 1977; Macka et 
al., 1978; Cain and Allen, 1980; Stamm, 1980; see also Chapter 6) .