Temperature Response of Aerobic Methane-Oxidizing Bacteria in Lake Sediments from King George Island, Maritime Antarctica.

Methane (CH4) is a major greenhouse gas that contributes substantially to global warming. The release of biogenic CH4 into the atmosphere is a critical factor in global climate change and can be enhanced by increasing temperature. Over the past 50 years, Maritime Antarctica has been among the most rapidly warming regions of the planet. Methane-oxidizing bacteria (MOB) can oxidize a substantial fraction of the CH4 produced by methanogenic archaea before it reaches the atmosphere. However, a major knowledge gap in the global CH4 cycle in the Southern Ocean and Antarctica concerns its biological consumption by MOB, which act as an important biological sink. Although temperature is known to strongly influence CH₄ oxidation rates, its effects on the structure of MOB communities and their associated phospholipid fatty acid (PLFA) profiles in polar environments remain poorly understood. In this study, the effect of temperature on the structure of the active community of aerobic MOB in the sediment of a lake on Fildes Peninsula in Maritime Antarctica was investigated using stable isotope probing of phospholipid fatty acids (PLFA-SIP) and 16S rRNA gene amplicon sequencing. Differential abundance analysis of microcosms incubated at 5 and 20 °C for 20 and 40 days showed Methylobacter and Crenothrix as the main MOB at both temperatures, while PLFA C16:1ω7c and C16:1ω5c, biomarkers of gammaproteobacterial MOB, increased their concentration. The rise in temperature from 5 to 20 °C decreased the diversity of the MOB community, suggesting certain vulnerability due to lack of redundancy of function. This study provides new insights into the impact of temperature on the structure of MOB and the total bacterial community in a polar lake system.