A marineChlamydomonassp. emerging as an algal model

The freshwater microalgaChlamydomonas reinhardtii, which lives in wet soil, has served for decades as a model for numerous biological processes, and many tools have been introduced for this organism. Here, we have established a stable nuclear transformation for its marine counterpart,Chlamydomonassp. SAG25.89, by fusing specificcis‐acting elements from itsActingene with the gene providing hygromycin resistance and using an elaborated electroporation protocol. LikeC. reinhardtii,Chlamydomonassp. has a high GC content, allowing reporter genes and selection markers to be applicable in both organisms.Chlamydomonassp. grows purely photoautotrophically and requires ammonia as a nitrogen source because its nuclear genome lacks some of the genes required for nitrogen metabolism. Interestingly, it can grow well under both low and very high salinities (up to 50 g · L‐1) rendering it as a model for osmotolerance. We further show thatChlamydomonassp. grows well from 15 to 28°C, but halts its growth at 32°C. The genome ofChlamydomonassp. contains some gene homologs the expression of which is regulated according to the ambient temperatures and/or confer thermal acclimation inC. reinhardtii. Thus, knowledge of temperature acclimation can now be compared to the marine species. Furthermore,Chlamydomonassp. can serve as a model for studying marine microbial interactions and for comparing mechanisms in freshwater and marine environments.Chlamydomonassp. was previously shown to be immobilized rapidly by a cyclic lipopeptide secreted from the antagonistic bacteriumPseudomonas protegensPF‐5, which deflagellatesC. reinhardtii.