Analysis of microbial methane oxidation capacity of landfill soil cover using quorum sensing

Landfill gas (LFG) has become the second-largest anthropogenic source of methane (CH4) emissions globally. CH4 is the second most significant greenhouse gas after carbon dioxide (CO2), thus it is crucial to mitigate the methane emission of landfills. The soil in landfill cover layers is rich in methane-oxidizing bacteria (MOB), which use CH4 as their sole carbon and energy source. However, during the microbial methane oxidation process, the oxidation rate tends to decrease over time. It is anticipated that extracellular polymeric substance (EPS) is one of the key factors governing the reduction in the methane oxidation rate. Furthermore, the quorum sensing (QS) is responsible to regulate the production of EPS in the microbial system. To clarify the mechanism of QS in controlling the microbial methane oxidation rate, laboratory experiments were conducted to study the correlations between the oxidation rate of MOB, the EPS content and the concentration of AHLs signaling molecules and to elucidate the regulatory mechanism of the QS on the microbial methane oxidation rate. The following conclusions were drawn: It is observed that the EPS produced by MOB can inhibit their methane oxidation rate. The addition of AHLs increases the EPS content produced by MOB. It is postulated that in the QS system of MOB, AHLs signaling molecules stimulate production of EPS, and its accumulation inhibits methane oxidation rate of MOB. Thus, the QS would provide a new perspective for the mitigation measures for methane emission in landfills.