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Unicellular cyanobacterium symbiotic with a single-celled eukaryotic alga

TitleUnicellular cyanobacterium symbiotic with a single-celled eukaryotic alga
Publication TypeJournal Article
Year of Publication2012
AuthorsThompson AW, Foster RA, Krupke A, Carter BJ, Musat N, Vaulot D, Kuypers MMM, Zehr JP
Keywords2012, MicroB3, rcc, sbr_phyto_dipo, SBR_Phyto_DPO

Symbioses between nitrogen (N)2–fixing prokaryotes and photosynthetic eukaryotes are important for nitrogen acquisition in N-limited environments. Recently, a widely distributed planktonic uncultured nitrogen-fixing cyanobacterium (UCYN-A) was found to have unprecedented genome reduction, including the lack of oxygen-evolving photosystem II and the tricarboxylic acid cycle, which suggested partnership in a symbiosis. We showed that UCYN-A has a symbiotic association with a unicellular prymnesiophyte, closely related to calcifying taxa present in the fossil record. The partnership is mutualistic, because the prymnesiophyte receives fixed N in exchange for transferring fixed carbon to UCYN-A. This unusual partnership between a cyanobacterium and a unicellular alga is a model for symbiosis and is analogous to plastid and organismal evolution, and if calcifying, may have important implications for past and present oceanic N2 fixation.