Abstract
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-Ch2T was isolated and studied using polyphasic taxonomy approach and genome sequencing. The strain HO-Ch2T grew optimally at 28 °C, pH 8.0, and 1–2% (w/v) NaCl. The 16S rRNA gene sequence of the strain HO-Ch2T had 98.8% similarity with the sequence of Actinotalea ferrariae CF5-4T. The genomic DNA G + C content of strain HO-Ch2T was 73.4%. The average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values between the genome of strain HO-Ch2T and Actinotalea 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-Ch2T (= VKM Ac-2850T = KCTC 49656T) as the type strain of a new species within the genus Actinotalea, with the name Actinotalea subterranea sp. nov. Based on the phylogenomic analysis of 187 genomes of Actinobacteria we propose the taxonomic revision of the genera Actinotalea and Pseudactinotalea and of the family Actinotaleaceae. We also propose the reclassification of Cellulomonas carbonis as Actinotalea carbonis comb. nov., Cellulomonas bogoriensis as Actinotalea bogoriensis comb. nov., Actinotalea caeni as Pseudactinotalea caeni comb. nov., and the transfer of the genus Pseudactinotalea to the family Ruaniaceae of the order Ruaniales.
Highlights
Oil field exploitation results in the exhaustion of oil reserves, oil biodegradation, and a decrease in oil quality
Results of the 16S rRNA gene sequence and core-genome analysis, the average nucleotide identity (ANI), and in silico DNA–DNA hybridization, as well as the phenotypic and chemotaxonomic characterization supported the classification of strains
Using the 16S rRNA gene sequences and genome sequences from the reference type strains of the class Actinomycetia from the GenBank database, the phylogenomic and pangenomic comparison was performed. These data elucidated the phylogenetic relationships among the genera Actinotalea, Pseudactinotalea, and Cellulomonas and confirmed the reclassification of Cellulomonas carbonis and Cellulomonas bogoriensis as new combinations within the genus Actinotalea and the transfer of the genus Pseudactinotalea to the family Ruaniaceae of the order Ruaniales
Summary
Oil field exploitation results in the exhaustion of oil reserves, oil biodegradation, and a decrease in oil quality. Microbial anaerobic oil degradation in oil fields is considered among the processes of transformation of certified light oil to heavy oil and into bitumen [1]. Oil reservoirs do not contain free oxygen. Under these conditions, the possible electron acceptors for microorganisms are CO2 , sulfate, sulfur and other oxidized sulfur. Microorganisms 2022, 10, 378 compounds, or iron hydroxides [2,3]. Nitrate and other nitrogen oxides do not occur in formation water. In this ecosystem, oil is the main source of organic matter
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