Girguis, P, R, Monterey Bay Aquarium Research Institute, Moss Landing, USA, girguis@mbari.org
Cozen, A, E, University of California Santa Cruz, Santa Cruz, USA, acozen@es.ucsc.edu
DeLong, E, , Massachusetts Institute of Technology, Boston, USA, delong@mit.edu

GROWTH AND POPULATION DYNAMICS OF METHANOTROPHIC ARCHAEA AND SULFATE REDUCING BACTERIA IN A CONTINUOUS FLOW BIOREACTOR

The consumption of methane in anoxic marine sediments is a biogeochemically significant process mediated by anaerobic methanotrophs. Anaerobic methanotrophic archaea have yet to be recovered in pure culture and key aspects of their ecology and physiology remain poorly understood To better characterize the growth and physiology of archaeal methanotrophs and their syntrophic sulfate-reducing bacterial partners, we used an anoxic, continuous flow bioreactor to incubate hydrocarbon seep sediments containing established methane oxidizing microbial populations, as well as benthic sediments without demonstrable methane oxidation rates. Sediments were sampled periodically and the growth rates of ANME-1 and ANME-2 archaea, as well as Desulfosarcina-like sulfate-reducing bacteria, were estimated using a quantitative polymerase chain reaction (qPCR). Sediment methane and sulfate concentrations and methane oxidation rates were also concomitantly determined. Here we report on the first growth rate estimates and population growth dynamics of both ANME-1 and ANME-2 anaerobic methanotrophs, as well as the syntrophic sulfate-reducing bacteria in low and high advective porewater flow regimes. These data demonstrate that anaerobic methanotrophs are capable of attaining substantial growth despite the putatively low energy yields from anaerobic methane oxidation.