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
Drainage waters at the metal mining areas often have low pH and high content of dissolved metals due to oxidation of sulfide minerals. Extreme conditions limit microbial diversity in- such ecosystems. A drainage water microbial community (6.5'C, pH 2.65) in an open pit at the Sherlovaya Gora polymetallic open-cast mine (Transbaikal region, Eastern Siberia, Russia) was studied using metagenomic techniques. Metagenome sequencing provided information for taxonomic and functional characterization of the micro- bial community. The majority of microorganisms belonged to a single uncultured lineage representing a new Betaproteobacteria species of the genus Gallionella. While no.acidophiles are known among the cultured members of the family Gallionellaceae, similar 16S rRNA gene sequences were detected in acid mine drain- ages. Bacteria ofthe genera Thiobacillus, Acidobacterium, Acidisphaera, and Acidithiobacillus,-which are com- mon in acid mine drainage environments, were the minor components of the community. Metagenomic data were -used to determine the almost complete (-3.4 Mb) composite genome of the new bacterial. lineage desig- nated Candidatus Gallionella acididurans ShG14-8. Genome analysis revealed that Fe(II) oxidation probably involved the cytochromes localized on the outer membrane of the cell. The electron transport chain included NADH dehydrogenase, a cytochrome bc1 complex, an alternative complex III, and cytochrome oxidases of the bd, cbb3, and bo3 types. Oxidation of reduced sulfur compounds probably involved the Sox system, sul- fide-quinone oxidoreductase, adenyl sulfate reductase, and sulfate adenyltransferase. The genes required for autotrophic carbon assimilation via the Calvin cycle were present, while no pathway for nitrogen fixation was revealed. High numbers of RND metal transporters and P type ATPases were probably responsible for resis- tance to heavy metals. The new microorganism was an aerobic chemolithoautotroph of the group of psychrotolerant iron- and sulfur-oxidizing acidophiles of the family Gallionellaceae, which are common in acid mine drainages.
