Unsuspected diversity among marine aerobic anoxygenic phototrophs.
Aerobic, anoxygenic, phototrophic bacteria containing bacteriochlorophyll a (Bchla) require oxygen for both growth and Bchla synthesis. Recent reports suggest that these bacteria are widely distributed in marine plankton, and that they may account for up to 5% of surface ocean photosynthetic electron transport and 11% of the total microbial community. Known planktonic anoxygenic phototrophs belong to only a few restricted groups within the Proteobacteria alpha-subclass. Here we report genomic analyses of the photosynthetic gene content and operon organization in naturally occurring marine bacteria. These photosynthetic gene clusters included some that most closely resembled those of Proteobacteria from the beta-subclass, which have never before been observed in marine environments. Furthermore, these photosynthetic genes were broadly distributed in marine plankton, and actively expressed in neritic bacterioplankton assemblages, indicating that the newly identified phototrophs were photosynthetically competent. Our data demonstrate that planktonic bacterial assemblages are not simply composed of one uniform, widespread class of anoxygenic phototrophs, as previously proposed; rather, these assemblages contain multiple, distantly related, photosynthetically active bacterial groups, including some unrelated to known and cultivated types.
Béjà
Oded
O
Monterey Bay Aquarium Research Institute, Moss Landing, California 95039-0628, USA.
Suzuki
Marcelino T
MT
Heidelberg
John F
JF
Nelson
William C
WC
Preston
Christina M
CM
Hamada
Tohru
T
Eisen
Jonathan A
JA
Fraser
Claire M
CM
DeLong
Edward F
EF
D020561:Alphaproteobacteria / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology; D001420:Bacteria, Aerobic / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D001426:Bacterial Proteins; D022202:Chromosomes, Artificial, Bacterial; D005798:Genes, Bacterial; D014644:Genetic Variation; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D010788:Photosynthesis / Q000235:genetics*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics; D010802:Phylogeny; D010839:Phytoplankton; D014871:Water Microbiology
D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; C094744:light-harvesting complex 1, Rhodospirillum