Aims: Crusts forming at the surface of liquid manure (slurry) during storage has been shown to harbor a potential for mitigating CH4 emissions. This study investigated the microbial community in surface crusts, with a focus on microorganisms related to CH4 metabolism. Methods and Results: Microbial communities in four crusts from cattle and swine slurries were investigated using DGGE 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 MOB community, whereas Methanocorpusculum was the predominant methanogen. Higher numbers of OTUs representing Type I than Type II MOB were found in all crusts. Potential CH4 oxidation rates were determined by incubations of crusts with CH4, and CH4 oxidization was observed in cattle, but not in swine slurry crusts. Conclusions: Slurry surface crusts harbor 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 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 contribute to mitigation of CH4 emissions from livestock manure management.
Journal of Applied Microbiology, 2014, Vol 117, Issue 4, p. 1066-1078