4 [16] Hydrate Ridge ANME-2a/2c and SRB consortia 1.4 MPa Fed-batch 7.5 [9] Conclusions After 286 days incubation in a simulated cold seep environment under

high methane pressure, ANME-2 and SRB in the sediment from Captain Arutyunov Mud Volcano were enriched. Based on biovolume calculation, the populations of ANME-2 and SRB increased for 12.5 times and 8.4 times. Within total biomass volume, 99.7% was accounted from aggregates. Therefore the incubation condition apparently favoured the cells to form aggregates, especially in small size (2<Ø≤5 μm), rather than to JNK-IN-8 live as single cells. No aggregate bigger than 15 μm in diameter was observed; they apparently divided after reaching a critical size. Based on the 16S rRNA gene clone library, the archaeal diversity was low, and contained only ANME-2 (88%) and MBG-D (12%). In contrast, the bacterial community was highly diverse. Methods Incubation condition In a previous AC220 nmr study, the sediment sample originally from Captain Arutyunov Mud Volcano (Gulf of Cadiz, North East Atlantic) was diluted 12 times with artificial sea water medium and incubated in a continuous high-pressure bioreactor at 15°C [11]. This bioreactor system was a simulator for cold seep ecosystems, where sulphate and high-pressure methane were supplied. Because the high apparent affinity for methane (37 mM) in SR-AOM reaction

and low dissolubility of methane in seawater (1.3 mM at 15°C at ambient pressure), it is necessary to supply high pressure methane to obtain high concentration of dissolved methane which can be directly used by microorganisms for high in vitro SR-AOM activity [11]. During this research, the reactor was operated in a fed-batch mode or a continuous mode. When it was in fed-batch mode, the methane pressures were switched between 1, 4.5 and 8 MPa. When it was in continuous mode, the methane pressure was either 1 or 8 MPa and the flow rate was 0.1 ml/min (HRT 100 hours). The SR-AOM activities under different operational conditions have been described previously [11]. To take a BIX 1294 chemical structure slurry sample, the

incubation vessel was open under a nitrogen atmosphere and manually stirred to make the slurry sample homogeneous. The slurry samples before (S1) and Resveratrol after (S2) 286 days incubation were fixed in 4% formaldehyde and stored at 4°C for cell staining. Additional slurry from S2 was stored at -20°C for DNA extraction and clone library analysis. Cell and aggregates quantification To assess the number and the size of cells and aggregates, DAPI (4′, 6-diamidino-2-phenylindole) staining was performed on S1 (after 2000 times dilution) and S2 (after 5600 times dilution). Subsequently, the samples were filtrated onto a circular GTTP polycarbonate filter (0.2 μm, Millipore, Germany) with a diameter of 2.5 cm. The number of cells (or aggregates) was quantified under a microscope (Zeiss, Carl Zeiss Microimaging GmbH, Germany) at 1,000 times magnification. The diameter of a single cell was assumed as 0.