Far‐red light promotes biofilm formation in the cyanobacterium Acaryochloris marina

Summary Light quantity and quality promotes ecological‐niche differentiation of photosynthetic organisms. The existence of cyanobacteria capable of performing photosynthesis using red‐shifted chlorophylls, chlorophyll d and f, reduces competition between species in light‐limiting environments, and permits them to thrive in niches enriched in far‐red light. We examined global transcriptome changes due to changing the culture light conditions in Acaryochloris marina, a chlorophyll d‐containing cyanobacterium. We identified the functional category of ‘photosynthesis’ as the most down‐regulated and the category of ‘cell wall/membrane biogenesis’ as the most up‐regulated through a functional enrichment analysis of genes differentially expressed. Within the category of ‘cell wall/membrane biogenesis’, genes encoding glycosysltransferases accumulated the most in response to far‐red light. Further experimental results confirmed that cells grown under far‐red light form biofilms with a significantly increased adherence compared to cells grown under white light. Taken together, these results indicate that Acaryochloris marina shifts its lifestyle from a planktonic state under white light to an immobilized state under far‐red light.