Physiological and Genomic Characterization of sp. nov. from Oil-Degrading Methanogenic Enrichment and Reclassification of the Family .

The goal of the present work was to determine the diversity of prokaryotes involved in anaerobic oil degradation in oil fields. The composition of the anaerobic oil-degrading methanogenic enrichment obtained from an oil reservoir was determined by 16S rRNA-based survey, and the facultatively anaerobic chemoorganotrophic bacterial strain HO-Ch2 was isolated and studied using polyphasic taxonomy approach and genome sequencing. The strain HO-Ch2 grew optimally at 28 °C, pH 8.0, and 1-2% (/) NaCl. The 16S rRNA gene sequence of the strain HO-Ch2 had 98.8% similarity with the sequence of CF5-4. The genomic DNA G + C content of strain HO-Ch2 was 73.4%. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the genome of strain HO-Ch2 and genomes were 79.8-82.0% and 20.5-22.2%, respectively, i.e., below the thresholds for species delineation. Based on the phylogenomic, phenotypic, and chemotaxonomic characterization, we propose strain HO-Ch2 (= VKM Ac-2850 = KCTC 49656) as the type strain of a new species within the genus , with the name sp. nov. Based on the phylogenomic analysis of 187 genomes of we propose the taxonomic revision of the genera and and of the family . We also propose the reclassification of as comb. nov., as comb. nov., as comb. nov., and the transfer of the genus to the family of the order .