Pervasive mixotrophy: genomic and metagenomic evidence for widespread organic compound uptake potential in marine autotrophs

Yelton, A.P. ... et. al.-- 17th Ocean Sciences Meeting, 23-28 February 2014, Honolulu, Hawaii USAPhotoheterotrophy or mixotrophy, the assimilation of organic compounds by autotrophs, has recently been demonstrated in both of the major marine cyanobacteria, Prochlorococcus spp. and Synechococcus spp. However, the ubiquity of this lifestyle remains unclear. Here we analyze metagenomic data from sixty-eight stations in all of the major oceans from the Tara Oceans expedition. This data has made it possible for the first time to track the global prokaryotic mixotrophic potential. Taxonomic assignment of organic compound uptake-related genes indicates that many (up to 29%) originate in genomes of “autotrophs”. Prochlorococcus spp. in particular have many organic compound uptake and metabolism genes. Additional data from forty-eight cultured isolates and single cell genomes indicates that Prochlorococcus ecotypes have differential capabilities to take up and catabolize organic compounds with strains belonging to the LL IV clade having the largest number of these genes. Metagenomic data demonstrate more organic compound uptake potential and a different gene complement for deep euphotic zone and mesopelagic Prochlorococcus. Overall, the cyanobacterial genetic potential for mixotrophy is globally distributed and extensive, suggesting cyanobacteria play an important role in oceanic secondary productivityPeer Reviewe