title: Methane production by phosphate-starved SAR11 chemoheterotrophic marine bacteria.
abstract: The oxygenated surface waters of the world's oceans are supersaturated with methane relative to the atmosphere, a phenomenon termed the 'marine methane paradox'. The production of methylphosphonic acid (MPn) by marine archaea related to Nitrosopumilus maritimus and subsequent decomposition of MPn by phosphate-starved bacterioplankton may partially explain the excess methane in surface waters. Here we show that Pelagibacterales sp. strain HTCC7211, an isolate of the SAR11 clade of marine α-proteobacteria, produces methane from MPn, stoichiometric to phosphorus consumption, when starved for phosphate. Gene transcripts encoding phosphonate transport and hydrolysis proteins are upregulated under phosphate limitation, suggesting a genetic basis for the methanogenic phenotype. Strain HTCC7211 can also use 2-aminoethylphosphonate and assorted phosphate esters for phosphorus nutrition. Despite strain-specific differences in phosphorus utilization, these findings identify Pelagibacterales bacteria as a source of biogenic methane and further implicate phosphate starvation of chemoheterotrophic bacteria in the long-observed methane supersaturation in oxygenated waters.
authors.affiliation: 1] Department of Microbiology, Oregon State University, Corvallis, Oregon 97331, USA [2] [3].
authors.forename: Paul
authors.initials: P
authors.lastname: Carini
authors.affiliation: 1] College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA [2].
authors.forename: Angelicque E
authors.initials: AE
authors.lastname: White
authors.affiliation: Department of Microbiology, Oregon State University, Corvallis, Oregon 97331, USA.
authors.forename: Emily O
authors.initials: EO
authors.lastname: Campbell
authors.affiliation: Department of Microbiology, Oregon State University, Corvallis, Oregon 97331, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Giovannoni
mesh_terms: D020561:Alphaproteobacteria / Q000378:metabolism*; D008697:Methane / Q000378:metabolism*; D009943:Organophosphorus Compounds / Q000378:metabolism*; D010710:Phosphates
chemical_list: D009943:Organophosphorus Compounds; D010710:Phosphates; C032627:methylphosphonic acid; D008697:Methane