Isolation and electroactive characteristics of a methane-oxidation promoting Pseudomonas putida P7

Abstract:

[Objective] To analyze the physiological and electrochemical characteristics of a methanotrophs-associated bacteria isolated from the methanotrophic enrichments in the Yellow River Delta wetland soil, and to explore their effect on the methane oxidation process. [Methods] High-throughput sequencing was used to analyze microbial community of methanotrophic enrichments. The methanotrophs-associated strain was isolated using plate smearing and scribing method and initially identified by 16S rRNA gene sequencing. The morphology of the isolate was depicted by scanning electron microscopy. Gas chromatography was used to analyze the methane concentration, which showed the ability of utilizing methane and influence of improving methane oxidation by methanotroph. Two-chamber microbial fuel cells and Differential Pulse Voltammetry were used to test the electrochemical activity. [Results] The microbial community of methanotrophic enrichments from incubation of Yellow River Delta wetland soil included methanotrophs Methylobacter and other accompanying genera. We isolated a methanol-metabolizing bacterium, Pseudomonas putida P7 (with the similarity of 99.79%) which was a rod bacterium with the length between 1.5 μm and 2.5 μm and width about 0.5 μm. The GC analysis showed that this strain could not use methane but improved methane oxidation (P<0.05). The maximum current density was 28 mA/m², and the results of DPV revealed that the oxidation peak and reduction peak occurred at -0.17 V and -0.25 V, respectively. [Conclusion] We successfully isolated an electrochemical activity microbe, Pseudomonas putida P7, with ability of improving methane oxidation. This study deepened the understanding of the physiological characteristics and functions of the methanotroph-associated bacteria in the process of methane oxidation.