ABSTRACT
Activity and growth of anaerobic methanotrophs (ANME) largely depends on the methane availability. High pressure incubation has shown to be more effective way for the study of anaerobic oxidation of methane (AOM) and enhance the growth rate of ANME. The main aim of this study is to investigate the effect of the methane partial pressure and temperature on anaerobic oxidation of methane and sulfate reduction activities by highly enriched ANME-2a community. The biomass containing ANME-2 was incubated in different pressure and temperature gradients for 80 days, i.e. 2 MPa, 10 MPa, 20 MPa and 30 MPa at 15°C to explore the AOM activity and monitor the response of microbial community at different pressures. The temperature used for the incubations were 4°C, 15°C and 25°C to study the response of the microbial community with temperature. The incubation at 10 MPa pressure and 15°C temperature showed the most active condition for the studied ANME-2 phylotype, whereas activity with 2 MPa pressure at 15°C was almost comparative to the response at 10 MPa pressure. The incubations at 20 MPa and 30 MPa pressure showed the depletion in activities after 30 days. Incubations at 4°C and 25°C at 10 MPa showed the minimum activity. Further, the microbial community analysis showed the shift in bacterial community composition after incubation in different conditions; however the archaeal community was remained stable. Thus, the finding of 15°C at 10 MPa pressure as most favorable condition for studied ANME-2 activity, suggesting the link with the biomass origin in situ pressure and temperature which is almost 10 MPa and 15°C respectively. The retardation of microbial activity at higher pressure of 20 MPa and 30 MPa in this study, also suggests the studied ANME cells might be influenced by increasing pressure and the ANME might not be piezophiles.
