Genome Analyses and Genome-Centered Metatranscriptomics of Methanothermobacter wolfeii Strain SIV6, Isolated from a Thermophilic Production-Scale Biogas Fermenter

Abstract

In the thermophilic biogas-producing microbial community, the genus <i>Methanothermobacter</i> was previously described to be frequently abundant. The aim of this study was to establish and analyze the genome sequence of the archaeal strain <i>Methanothermobacter wolfeii</i> SIV6 originating from a thermophilic industrial-scale biogas fermenter and compare it to related reference genomes. The circular chromosome has a size of 1,686,891 bases, featuring a GC content of 48.89%. Comparative analyses considering three completely sequenced <i>Methanothermobacter</i> strains revealed a core genome of 1494 coding sequences and 16 strain specific genes for <i>M. wolfeii</i> SIV6, which include glycosyltransferases and CRISPR/<i>cas</i> associated genes. Moreover, <i>M. wolfeii</i> SIV6 harbors all genes for the hydrogenotrophic methanogenesis pathway and genome-centered metatranscriptomics indicates the high metabolic activity of this strain, with 25.18% of all transcripts per million (TPM) belong to the hydrogenotrophic methanogenesis pathway and 18.02% of these TPM exclusively belonging to the <i>mcr</i> operon. This operon encodes the different subunits of the enzyme methyl-coenzyme M reductase (EC: 2.8.4.1), which catalyzes the final and rate-limiting step during methanogenesis. Finally, fragment recruitment of metagenomic reads from the thermophilic biogas fermenter on the SIV6 genome showed that the strain is abundant (1.2%) within the indigenous microbial community. Detailed analysis of the archaeal isolate <i>M. wolfeii</i> SIV6 indicates its role and function within the microbial community of the thermophilic biogas fermenter, towards a better understanding of the biogas production process and a microbial-based management of this complex process.