Response characteristics of aerobic methane oxidation to oxygen concentration in marine habitats

It is not clear whether methanotrophs and the aerobic methane oxidation of marine habitats are unique and how they respond to oxygen concentration. In this paper, experimental investigations on the aerobic oxidation of methane were conducted under different oxygen concentrations (0%、1%、10% and 50%), using fresh seabed sediments as the source of methanotrophs. The results show that aerobic methane oxidation is rejective to anoxic condition (0%). Both the oxidation rate and abundance of methanotrophs decrease as the oxygen concentration increases. When oxygen concentration increases from 1% to 50%, the oxidation rate will decrease by about 15 times, and the total abundance of methanotrophs decreases by two orders in magnitude. The dominant methanotrophs belong to type I-Methylobacter, which consist of Methylobacter leteus and Methylobacter whittenburyi. When oxygen concentration increases, the proportion of Methylobacter leteus decreases, while that of Methylobacter whittenburyi increases. The study further suggests that the optimum oxygen concentration of methanotrophs and the aerobic methane oxidation is 1%, which is very close to the original environment of the sampling location. It means that the optimum oxygen concentration of methanotrophs will gradually approach the original living environment under a long-term acclimatization in specific biotope such as that with low oxygen concentration under low temperature and high pressure.