title: High abundances of aerobic anoxygenic photosynthetic bacteria in the South Pacific Ocean.
abstract: Little is known about the abundance, distribution, and ecology of aerobic anoxygenic phototrophic (AAP) bacteria, particularly in oligotrophic environments, which represent 60% of the ocean. We investigated the abundance of AAP bacteria across the South Pacific Ocean, including the center of the gyre, the most oligotrophic water body of the world ocean. AAP bacteria, Prochlorococcus, and total prokaryotic abundances, as well as bacteriochlorophyll a (BChl a) and divinyl-chlorophyll a concentrations, were measured at several depths in the photic zone along a gradient of oligotrophic conditions. The abundances of AAP bacteria and Prochlorococcus were high, together accounting for up to 58% of the total prokaryotic community. The abundance of AAP bacteria alone was up to 1.94 x 10(5) cells ml(-1) and as high as 24% of the overall community. These measurements were consistent with the high BChl a concentrations (up to 3.32 x 10(-3) microg liter(-1)) found at all stations. However, the BChl a content per AAP bacterial cell was low, suggesting that AAP bacteria are mostly heterotrophic organisms. Interestingly, the biovolume and therefore biomass of AAP bacteria was on average twofold higher than that of other prokaryotic cells. This study demonstrates that AAP bacteria can be abundant in various oligotrophic conditions, including the most oligotrophic regime of the world ocean, and can account for a large part of the bacterioplanktonic carbon stock.
authors.affiliation: Observatoire Océanologique de Banyuls, Université Pierre et Marie Curie-Paris 6, UMR7621-INSU-CNRS, BP44, F-66650 Banyuls-sur-Mer, France.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Lami
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Cottrell
authors.forename: Joséphine
authors.initials: J
authors.lastname: Ras
authors.forename: Osvaldo
authors.initials: O
authors.lastname: Ulloa
authors.forename: Ingrid
authors.initials: I
authors.lastname: Obernosterer
authors.forename: Hervé
authors.initials: H
authors.lastname: Claustre
authors.forename: David L
authors.initials: DL
authors.lastname: Kirchman
authors.forename: Philippe
authors.initials: P
authors.lastname: Lebaron
mesh_terms: D001420:Bacteria, Aerobic / Q000302:isolation & purification* / Q000378:metabolism; D025541:Bacteriochlorophyll A / Q000378:metabolism; D018533:Biomass; D002734:Chlorophyll / Q000378:metabolism; D015169:Colony Count, Microbial; D017753:Ecosystem; D010140:Pacific Ocean; D010788:Photosynthesis; D010839:Phytoplankton / Q000302:isolation & purification / Q000378:metabolism; D048929:Prochlorococcus / Q000302:isolation & purification / Q000378:metabolism; D012623:Seawater / Q000382:microbiology*; D014753:Vinyl Compounds / Q000378:metabolism
chemical_list: D025541:Bacteriochlorophyll A; D014753:Vinyl Compounds; C510432:divinyl chlorophyll a; D002734:Chlorophyll