Insights into the annotated genome sequence of Methanoculleus bourgensis MS2T, related to dominant methanogens in biogas-producing plants

• First completely sequenced genome of Methanoculleus bourgensis isolated from a sewage sludge digester.
• Potential adaptive genome features were identified.
• Methanoculleus bourgensis strain MS2T is highly related to dominant methanogens of a production-scale biogas plant.

The final step of the biogas production process, the methanogenesis, is frequently dominated by members of the genus Methanoculleus. In particular, the species Methanoculleus bourgensis was identified to play a role in different biogas reactor systems. The genome of the type strain M. bourgensis MS2T, originally isolated from a sewage sludge digestor, was completely sequenced to analyze putative adaptive genome features conferring competitiveness within biogas reactor environments to the strain. Sequencing and assembly of the M. bourgensis MS2T genome yielded a chromosome with a size of 2,789,773 bp. Comparative analysis of M. bourgensis MS2T and Methanoculleus marisnigri JR1 revealed significant similarities. The absence of genes for a putative ammonium uptake system may indicate that M. bourgensis MS2T is adapted to environments rich in ammonium/ammonia. Specific genes featuring predicted functions in the context of osmolyte production were detected in the genome of M. bourgensis MS2T. Mapping of metagenome sequences derived from a production-scale biogas plant revealed that M. bourgensis MS2T almost completely comprises the genetic information of dominant methanogens present in the biogas reactor analyzed. Hence, availability of the M. bourgensis MS2T genome sequence may be valuable regarding further research addressing the performance of Methanoculleus species in agricultural biogas plants.