Temperature response of aerobic methane-oxidizing bacteria in lake sediments from King George Island, Maritime Antarctica

Methane (CH4) is a crucial greenhouse gas, and makes a major contribution to global warming. The release of biogenic CH4 into the atmosphere is a critical factor in global climate change, and can be promoted by increased temperature. Over the past 50 years, Maritime Antarctica has been among the most rapidly warming regions of the planet. Methane oxidizing bacteria (MOB) play a crucial role in CH4 oxidation in diverse ecosystems acting as a major biological sink. However, understanding of CH₄ biological sinks in Maritime Antarctica and the impact of temperature on the structure of MOB remains limited. MOB exhibit phospholipid fatty acids (PLFA) profiles of their cell membranes, and their identification can be used as biomarkers. 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 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.