Physiological, chemotaxonomic and genomic characterization of two novel piezotolerant bacteria of the family Marinifilaceae isolated from sulfidic waters of the Black Sea

Abstract Diversity analyses of microbial enrichments obtained from deep sulfidic water (2000 m) collected from the Black Sea indicated the presence of eleven novel putative lineages of bacteria affiliated with the family Marinifilaceae of the phylum Bacteroidetes. We obtained pure cultures of four strains (i.e. M1PT, M3P, A4T and 44) of this family, which can be grouped into two different clades based on their 16S rRNA gene sequences. All four strains were Gram-negative, rod-shaped and facultative anaerobic bacteria. The genomes of all strains were sequenced and physiological analyses were performed. All strains utilized a wide range of carbon sources, which was supported by the presence of the pathways involved in carbon utilization encoded by their genomes. The strains were able to grow at elevated hydrostatic pressure (up to 50 MPa), which coincided with an increased production of unsaturated and branched fatty acids and a decrease in hydroxy fatty acids. Intact polar lipid analysis of all four strains showed the production of ornithine lipids, phosphatidylethanolamines and capnine lipids as major intact polar lipids (IPLs). Genes involved in the hopanoid biosynthesis were also identified. However, bacteriohopanepolyols (BHPs) were not detected in either of the strains. Based on distinct physiological, chemotaxonomic, genotypic and phylogenetic differences to other members of the genera Ancylomarina and Labilibaculum, it was concluded that strain M1PT and A4T represent two novel species for which the names Ancylomarina euxinus sp. nov. and Labilibaculum euxinus sp. nov., respectively, are proposed.