Methanotrophs, methanogens and microbial community structure in livestock slurry surface crusts
Crusts forming at the surface of liquid manure (slurry) during storage have been shown to harbour a potential for mitigating CH4 emissions. This study investigated the microbial community in surface crusts, with a focus on micro-organisms related to CH4 metabolism.
Methods and Results
Microbial communities in four crusts from cattle and swine slurries were investigated using denaturing gradient gel electrophoresis and tag-encoded amplicon pyrosequencing. All crusts had distinct compositions of bacteria and archaea. The genera Methylobacter, Methylomicrobium, Methylomonas, and Methylosarcina of Type I, and Methylocystis of Type II, dominated the methane-oxidizing bacteria (MOB) community, whereas Methanocorpusculum was the predominant methanogen. Higher numbers of operational taxonomic units (OTUs) representing Type I than Type II MOB were found in all crusts. Potential CH4 oxidation rates were determined by incubating crusts with CH4, and CH4 oxidization was observed in cattle, but not in swine slurry crusts.
Slurry surface crusts harbour a diverse microbial community. Type I MOB are more diverse and abundant than Type II MOB in this environment. The distinct CH4 oxidation rates could be related to microbial compositions.
Significance and Impact of the Study
This study is the first to present the overall microbial community structure in slurry surface crusts. A better understanding of microbial community in surface crusts could support strategies for mitigation of CH4 emissions from livestock manure management.