Figure 1 from Salomé and Merchant 2019. Taxonomic Basis of Chlamydomonas and Volvox. Ehrenberg’s drawings of Chlamydomonas and Volvox cells, published in 1838. Cells that belong to the same species are indicated by Roman numerals in the right panel. I, Gonium pectorale; II, Gonium punctatum; III, Gonium tranquillum; IV, Gonium hyalinum; V, Gonium glaucum; VI, Eudorina elegans; VII, Syncrypta volvox; VIII, Sphaerosira volvox; IX, Synura uvella; X, Chlamidomonas pulvisculus; XI, Uroglena volvox. The species was identified as Chlamidomonas pulvisculus but renamed Chlamydomonas reinhardtii in 1888.

In a new(-ish) article in The Plant Cell, Patrice Salomé and Sabeeha Merchant review the history and utility of the green alga Chlamydomonas reinhardtii as a model organism. The article discusses the advantages of Chlamy as a model organism, the scientific questions it has been used to explore, the history of Chlamy research, the characteristics of the species, the existing resources and databases, and genetic and genomic techniques. It’s a good introduction to Chlamy research in a more easily-digestible form than the massive, three-volume Chlamydomonas Sourcebook.

I found the historical section particularly interesting, describing the original description (as Chlamydomonas pulvisculus) by Christian Ehrenberg (see Figure 1 above), early genetic work by Franz Moewus and Gilbert Smith, the subsequent generation of mutants during the 1950s and ’60s, and the development of transformation techniques starting in the ’90s. The descriptions of the vegetative and sexual life cycles are short but informative:

Figure 3A from Salomé and Merchant 2019. The sexual and vegetative cycles of C. reinhardtii. Adapted from a figure originally drawn by Karen VanWinkle-Swift and published in The Chlamydomonas Sourcebook, Volume 1 (Harris, 2008).

Perhaps the most valuable sections for students considering Chlamydomonas research are those on the available techniques and resources. Methods for transformation of nuclear and organelle genomes are described briefly but with sufficient references for further detail. Databases, culture collections, and mutant collections are also described.

Throughout, the article is optimistic about the future of Chlamydomonas research, while acknowledging that important challenges remain:

Chlamydomonas has had a long, rich history as a model organism for studying photosynthesis and cilia biology…Chlamydomonas now finds itself at another turning point in its long history: large-scale mutant collections bring hypothesis-driven science and reverse genetics within grasp, while we wait for the optimization of genome-editing methods.

Many classical mutants remain uncharacterized (at the molecular level), while large insertional mutant collections are being screened for phenotypes of interest, with thousands of algal genes not annotated or associated with a clear function…As the most thoroughly characterized unicellular alga, C. reinhardtii can transcend its impact in algal biology by becoming a model for future microalgae and biotechnology for decades to come.

Stable links:

Harris, E.H. 2009. The Chlamydomonas Sourcebook, Second Edition. San Diego, California: Academic Press.

Salomé, P.A. and Merchant, S.S. 2019. A series of fortunate events: introducing Chlamydomonas as a reference organism. Plant Cell, 31: 1682–1707. doi: 10.1105/tpc.18.00952