Effect of Pressure on the Diversity and Potential Activity of Aerobic Methanotrophs in Marine Sediments: A Case Study From the Shenhu Area, Northern South China Sea

High hydrostatic pressure in deep-sea environments potentially impacts microbial community diversity, the structure of cellular components and functions. The specific characteristics of aerobic methanotrophs originating from deep-sea environments and their responses to local pressure fluctuations in terms of community diversity and methane oxidation potential remain unexplored. This study investigates subsurface sediments rich in aerobic methanotrophs from the natural gas hydrate-bearing region in the Shenhu area, Northern South China Sea. By conducting aerobic oxidation of methane (AeOM) incubation experiments under various environmental pressures up to 10 MPa, the study aims to elucidate differences in microbial community diversity and AeOM rates. The results show a profound impact of pressure on both the taxonomic composition of bacterial and methanotrophic communities and their capacity for methane consumption. The key aerobic methanotrophs, that is, Methylococcales, exhibit a gradual decrease in composition as pressure rises. Accordingly, their AeOM rates also show a significant negative correlation with pressure (r = 0.986, P < 0.01). The composition of three dominant methanotrophic genera, that is, unclassified_Methylococcaceae, Methylobacter, and Methylocaldum, exhibited irregular fluctuations under varying pressure conditions, with the lowest abundance observed at 2 MPa. Our study also shows that unclassified_Methylococcaceae is the primary methanotroph that exhibits the main response to pressure changes in marine environments.