Aims: 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.
Conclusions: 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.
Keywords: denaturing gradient gel electrophoresis; livestock slurry surface crust; methane-oxidizing bacteria; methanogen; pyrosequencing.
© 2014 The Society for Applied Microbiology.