ABSTRACT
Bacteria play a key role in biogeochemical cycles in natural and anthropogenic ecosystems. In river ecosystems, bacteria intensively colonize silt sediments. Microorganisms are essential for energy conversion, biogeochemical nutrient cycling, pollutant degradation, and biotransformation of organic matter; therefore, bottom sediments can be a source of metabolically diverse microorganisms, including those with promise for industrial biotechnologies. The aim of this work was to isolate and study pure cultures of microorganisms - producers of industrially important enzymes and decomposers of organic matter - from bottom sediments of the Ob River. Pork fat and diesel fuel were used as substrates to obtain enrichment and pure cultures for selective cultivation of bacteria with lipolytic and hydrocarbon-oxidizing activity. A total of 21 pure cultures were isolated. The phylogenetic position of the obtained bacterial isolates was determined based on the analysis of 16S rRNA gene sequences. The strains isolated on selective media belonged to representatives of the genera Pseudomonas and Aeromonas (Gammaproteobacteria), and the genus Microvirgula (Betaproteobacteria). The ability of strains to grow on culture media containing pork fat, olive oil and diesel fuel was analyzed. The lipolytic activity of the isolates was evidenced by cultivation on a diagnostic medium containing 1 % tributyrin. The phylogenetic and metabolic diversity of the cultivated non-pathogenic bacterial strains with lipolytic and oil-oxidizing activity revealed in the study indicates the biotechnological potential of the isolates. The most promising strains were M. aerodenitrificans sp. LM1 and P. lini sp. KGS5K3, which not only exhibited lipolytic activity on the diagnostic medium with tributyrin in a wide temperature range, but also utilized diesel fuel, pork fat and olive oil.
ABSTRACT
The genome of Melioribacter roseus, one of two members of the recently described phylum Ignavibacteriae, was searched for the genes encoding proteins associated with copper transport or containing copper as cofactors, and the effect of Cu2+ concentration in the medium on M. roseus growth was investigated. Genomic analysis revealed a variety of copper-containing oxidoreductases in this facultative anaerobe. Three ATPases responsible for copper transport were identified. One of them (MROS_1511) was.probably involved in assembly of the copper-containing cytochrome c oxidase, while two others (MROS_0327 and MROS_0791) probably carried out a detoxification function. The presence of several copper-containing oxidoreductases and copper homeostasis systems in M. roseus is in agreement with the previously hypothesized origin of the phylum Ignavibacteriae from an aerobic ancestor common with those of Bacteroidetes and Chlorobi.
