Abstract
Advanced physicochemical and chemical absorption methods for chlorinated ethenes are feasible but incur high costs and leave traces of pollutants on the site. Biodegradation of such pollutants by anaerobic or aerobic bacteria is emerging as a potential alternative. Several mycobacteria including Mycolicibacterium aurum L1, Mycolicibacterium chubuense NBB4, Mycolicibacterium rhodesiae JS60, Mycolicibacterium rhodesiae NBB3 and Mycolicibacterium smegmatis JS623 have previously been described as assimilators of vinyl chloride (VC). In this study, we compared nucleotide sequence of VC cluster and performed a taxogenomic evaluation of these mycobacterial species. The results showed that the complete VC cluster was acquired by horizontal gene transfer and not intrinsic to the genus Mycobacterium sensu lato. These results also revealed the presence of an additional xcbF1 gene that seems to be involved in Coenzyme M biosynthesis, which is ultimately used in the VC degradation pathway. Furthermore, we suggest for the first time that S/N-Oxide reductase encoding gene was involved in the dissociation of the SsuABC transporters from the organosulfur, which play a crucial role in the Coenzyme M biosynthesis. Based on genomic data, M. aurum L1, M. chubuense NBB4, M. rhodesiae JS60, M. rhodesiae NBB3 and M. smegmatis JS623 were misclassified and form a novel species within the genus Mycobacterium sensu lato. Mycolicibacterium aurum L1T (CECT 8761T = DSM 6695T) was the subject of polyphasic taxonomic studies and showed ANI and dDDH values of 84.7 and 28.5% with its close phylogenetic neighbour, M. sphagni ATCC 33027T. Phenotypic, chemotaxonomic and genomic data considering strain L1T (CECT 8761T = DSM 6695T) as a type strain of novel species with the proposed name, Mycolicibacterium vinylchloridicum sp. nov.
Highlights
Chlorinated ethenes (CE) are one of the major contaminants of soil and groundwater due to its excessive use in several industries, such as polyvinylchloride industry and plastic manufactory
Mycobacterial strains showed a great adaptability to different contaminated terrestrial and aquatic environments through their ability to produce biosurfactants and to degrade chlorinated pollutants, such as Mycobacterium chubuense DSM 44219T and Mycobacterium obuense DSM 44075T (Tsukamura et al, 1981; Coleman et al, 2006; Satsuma and Masuda, 2012; Das et al, 2015). These latter strains together with Mycobacterium aurum species were transferred to the genus Mycolicibacterium defined after the taxonomic revision of the genus Mycobacterium based on comparative genomic studies by Gupta et al (2018)
The strain included in this study was obtained from CECT and the strain designation L1T was used in the whole manuscript to avoid confusion
Summary
Chlorinated ethenes (CE) are one of the major contaminants of soil and groundwater due to its excessive use in several industries, such as polyvinylchloride industry and plastic manufactory. Mycobacterial strains showed a great adaptability to different contaminated terrestrial and aquatic environments through their ability to produce biosurfactants and to degrade chlorinated pollutants, such as Mycobacterium chubuense DSM 44219T and Mycobacterium obuense DSM 44075T (Tsukamura et al, 1981; Coleman et al, 2006; Satsuma and Masuda, 2012; Das et al, 2015). These latter strains together with Mycobacterium aurum species were transferred to the genus Mycolicibacterium defined after the taxonomic revision of the genus Mycobacterium based on comparative genomic studies by Gupta et al (2018).
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