title: Growth and activity of ANME clades with different sulfate and sulfide concentrations in the presence of methane.
abstract: Extensive geochemical data showed that significant methane oxidation activity exists in marine sediments. The organisms responsible for this activity are anaerobic methane-oxidizing archaea (ANME) that occur in consortia with sulfate-reducing bacteria. A distinct zonation of different clades of ANME (ANME-1, ANME-2a/b, and ANME-2c) exists in marine sediments, which could be related to the localized concentrations of methane, sulfate, and sulfide. In order to test this hypothesis we performed long-term incubation of marine sediments under defined conditions with methane as a headspace gas: low or high sulfate (±4 and ±21 mM, respectively) in combination with low or high sulfide (±0.1 and ±4 mM, respectively) concentrations. Control incubations were also performed, with only methane, high sulfate, or high sulfide. Methane oxidation was monitored and growth of subtypes ANME-1, ANME-2a/b, and ANME-2c assessed using qPCR analysis. A preliminary archaeal community analysis was performed to gain insight into the ecological and taxonomic diversity. Almost all of the incubations with methane had methane oxidation activity, with the exception of the incubations with combined low sulfate and high sulfide concentrations. Sulfide inhibition occurred only with low sulfate concentrations, which could be due to the lower Gibbs free energy available as well as sulfide toxicity. ANME-2a/b appears to mainly grow in incubations which had high sulfate levels and methane oxidation activity, whereas ANME-1 did not show this distinction. ANME-2c only grew in incubations with only sulfate addition. These findings are consistent with previously published in situ profiling analysis of ANME subclusters in different marine sediments. Interestingly, since all ANME subtypes also grew in incubations with only methane or sulfate addition, ANME may also be able to perform anaerobic methane oxidation under substrate limited conditions or alternatively perform additional metabolic processes.
authors.affiliation: Laboratory of Microbiology, Wageningen University Wageningen, Netherlands.
authors.forename: Peer H A
authors.initials: PH
authors.lastname: Timmers
authors.affiliation: Laboratory of Microbiology, Wageningen University Wageningen, Netherlands.
authors.forename: H C A
authors.initials: HC
authors.lastname: Widjaja-Greefkes
authors.affiliation: Laboratory of Microbiology, Wageningen University Wageningen, Netherlands ; Laboratory of Systems and Synthetic Biology, Wageningen University Wageningen, Netherlands.
authors.forename: Javier
authors.initials: J
authors.lastname: Ramiro-Garcia
authors.affiliation: Laboratory of Microbiology, Wageningen University Wageningen, Netherlands ; European Centre of Excellence for Sustainable Water Technology Wetsus, Leeuwarden, Netherlands.
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Plugge
authors.affiliation: Laboratory of Microbiology, Wageningen University Wageningen, Netherlands ; Centre of Biological Engineering, University of Minho Braga, Portugal.
authors.forename: Alfons J M
authors.initials: AJ
authors.lastname: Stams
keywords: ANME; AOM; SR; methane oxidation; niche separation; sulfate reduction