Chlamydomonas reinhardtii

Chlamydomonas reinhardtii is a single-cell green alga about 10 micrometres in diameter that swims with two flagella. It has a cell wall made of hydroxyproline-rich glycoproteins, a large cup-shaped chloroplast, a large pyrenoid, and an eyespot that senses light. Chlamydomonas species are widely distributed worldwide in soil and fresh water. Chlamydomonas reinhardtii is an especially well studied biological model organism, partly due to its ease of culturing and the ability to manipulate its genetics. When illuminated, C. reinhardtii can grow photoautotrophically, but it can also grow in the dark if supplied with organic carbon. Commercially, C. reinhardtii is of interest for producing biopharmaceuticals and biofuel, as well being a valuable research tool in making hydrogen. The C. reinhardtii wild-type laboratory strain c137 (mt+) originates from an isolate collected near Amherst, Massachusetts, in 1945 by Gilbert M. Smith. The species' name has been spelled several different ways because of different transliterations of the name from Russian: reinhardi, reinhardii, and reinhardtii all refer to the same species, C. reinhardtii Dangeard. Chlamydomonas is used as a model organism for research on fundamental questions in cell and molecular biology such as: How do cells move? How do cells respond to light? How do cells recognize one another? How do cells generate regular, repeatable flagellar waveforms? How do cells regulate their proteome to control flagellar length? How do cells respond to changes in mineral nutrition? (nitrogen, sulfur, etc.) There are many known mutants of C. reinhardtii. These mutants are useful tools for studying a variety of biological processes, including flagellar motility, photosynthesis, and protein synthesis. Since Chlamydomonas species are normally haploid, the effects of mutations are seen immediately without further crosses. In 2007, the complete nuclear genome sequence of C. reinhardtii was published. Channelrhodopsin-1 and Channelrhodopsin-2, proteins that function as light-gated cation channels, were originally isolated from C.