SUMMARY: Chlamydomonas are common, single-celled green algae that are flagellated and can move around. They’re a strange cross between plants and protists. In this study, scientists subjected chlamydomonas to predation by paramecia (common freshwater ciliates) and observed that after about 750 generations, the chlamydomonas took on characteristics of multicellular life. Not only were the normally motile algae forming colonies, but the more advanced ones consisted of cells enclosed in the cell wall of the mother cell and cells that clumped together within an extracellular matrix (gooey material produced around the cells, similar to biofilm in bacteria). This experiment shows that single-celled organisms have the genetic ability to develop multicellular characteristics when put under selective pressure (none of the non-pressured algae showed this type of colony formation). It is also important to note that only 2 of the 5 focal groups developed clumping capability.
LESSON COMMENTS: Topics that can be covered include evolution, response to ecosystem changes, ecosystem relationships, genetics, and mitosis. If you’re doing a population activity either analog or computer simulation, this article can be used as supporting evidence and/or as a real life example of the results of change over time. Students can read it before or after the lab as either a pre-lab assignment or post-lab synthesis/analysis exercise. To go one step further, this article can be compared to the microbiome or antibiotic resistance articles in this database. Students can compare and contrast the differences between prokaryotes and eukaryotes, biofilm and extracellular matrix, bacterial colonies and multicellular structures.
Herron, M. D., Borin, J. M., Boswell, J. C., Walker, J., Chen, I. K., Knox, C. A., … Ratcliff, W. C. (2019). De novo origins of multicellularity in response to predation. Scientific reports, 9(1), 2328. doi:10.1038/s41598-019-39558-8