A Day (and Night) in the Life of Green Algae

Researchers uncover the diurnal functioning of reference algae important to the development of a variety of high-value bioproducts.

The Science

Single-cell green algae such as Chlamydomonas hold great potential for creating bioproducts and biofuels, but are greatly influenced by changes in their environment such as light and temperature. Scientists studied these algae under controlled conditions that mimicked day and night to learn how the genetic and biomolecular machinery of these algae responded to this daily rhythm.

The Impact

Over the course of 24 hours, land plants open and close their buds, sprout or lose leaves, and produce and consume sugars. Most of these and other activities in plants are driven by the Sun, leading to a circadian rhythm that allocates certain functions to the right time of the day or night. Green algae are thought to follow a similar pattern. Understanding how green algae change physiologically and metabolically over the course of a day will help scientists better predict how to make the best use of these algae to create or enhance the production of bioproducts and biofuels.


Chlamydomonas is an important reference model for photosynthesis and fermentation. To uncover the daily workings of these reference algae, scientists from the University of California at Los Angeles, Heinrich Heine University in Germany, University of Nebraska, and Pacific Northwest National Laboratory teamed with counterparts at EMSL, the Environmental Molecular Sciences Laboratory, which is a U.S. Department of Energy Office of Science user facility. They exposed the algae to conditions mimicking a day in nature, with light-dark cycles superimposed with warm-cool cycles. They then analyzed the inner workings of the genetic code and its products, including how certain genes and proteins matched measurements of pigments, select metabolites, and physiological parameters. The results yielded a number of insights. Nearly 85 percent of the algal genome changed throughout the day to coordinate cellular growth before cell division. Timing of changes in specific genes was dictated by their biological function. And, in contrast to conventional thinking, nighttime physiology proved to be a time of enhanced fermentation rather than a “quiet phase” with little activity. The rich dataset developed in this work will serve as a resource for other fundamental and applied research studies on algal productivity.

Principal Investigator(s)

Sabeeha Merchant
University of California, Los Angeles


This work was supported by the U.S. Department of Energy’s Office of Science (Office of Biological and Environmental Research), including support of the Environmental Molecular Sciences Laboratory (EMSL), a DOE Office of Science User Facility; the European Molecular Biology Organization; and the National Science Foundation.


Strenkert, D., S. Schmollinger, S.D. Gallaher, P.A. Salomé, S.O. Purvine, C.D. Nicora, T. Mettler-Altmann, E. Soubeyrand, A.P.M. Weber, M. Lipton, G.J. Basset, and S.S. Merchant. “Multiomics resolution of molecular events during a day in the life of Chlamydomonas.” Proceedings of the National Academy of Sciences 116(6), 2374-2383 (2019). DOI:10.1073/pnas.1815238116