SummaryBacteria of the genus Citrobacter are found in soil, water, the intestinal tract of animals, human clinical samples (urine, sputum, blood, wound drainage, etc.), also in wastewaters and waste dumps of mines. Gram-negative bacteria SR35, capable of reducing sulfur and sulfate ions, were isolated from the waste dump of the Nadiya coal mine, Chervonograd Mining and Industrial district (Lviv region, Ukraine). The work aimed to identify and study morphological, physical and chemical properties (cell shape, size, Gram staining, sporulation, motility, oxygen requirements, ability to form H2S, utilization of carbon sources, catalase activity, oxidase activity) of isolate SR35. Methods. We used standard microbiological and biochemical research methods (microbial culture, microscopy methods, determination of amilase, lipase activity). Chromosomal DNA was isolated by the method of soft lysis. The 16S rRNA gene was amplified using universal primers 27F and 1492R. It was sequenced by the Sanger method. Phylogenetic reconstruction was performed using the MEGA X program. Identification of isolates was carried out based on both the sequence of the 16S rRNA gene and physiological and biochemical properties. Results. The studied bacteria are rods (0.5–0.8×1.5–2.0μm), which form chains and are capable of reducing nitrate and sulfate ions and assimilating several carbon sources. Glucose, lactose, mannose, mannitol, and inositol are fermented with the formation of acid. Motile. Catalase positive, oxidase negative. Form H2S during growth in Kligler’s medium. According to the results of pairwise alignment of the isolate’s 16S rRNA gene sequence, the highest percentage of identity with representatives of the genus Citrobacter was established (99.23–99.86% identity, coverage 98%) and it was confirmed by phylogenetic reconstruction. Citrobacter sp. SR35 is resistant to 2 μM cadmium (II), 5 mM iron (II), 0.25 mM cobalt (II), 10 mM manganese (II), 0.5 mM copper (II), and 0.1 mM chromium (VI). Conclusions. According to the results of sequencing of the 16S rRNA (accession number GenBank OP279754) gene, and physiological, and biochemical characteristics (oxidase, catalase, metabolism of carbon sources, production of H2S, etc.), it was established that isolate SR35 belongs to the genus Citrobacter.

The microbiota plays an important role in the processes of plant overgrowth of coal mine waste dumps, enabling the transformation of numerous compounds into forms available to plants. The overgrowth of coal mine dumps is influenced by many factors. Pioneers are plant species that have a wide ecological and phytocenotic amplitude. Calamagrostis epigeios (L.) Roth. occupies a special place among them. The composition of the microbiota of the rhizosphere zone of C. epigeios was studied in relation to the age of the plants and the stage of the succession of the “Vizeyska” mine dump (Ukraine). It was established and confirmed as a result of two-factor variance analysis that the growth phase of C. epigeios and the stage of the succession of coal mine waste dumps have different effects on the number of microorganisms from the rhizosphere zone of plants. The number of pedotrophic microorganisms, microorganisms that metabolize nitrogen of organic compounds, cellulose-degrading microorganisms, and microscopic fungi depended more on the age of C. epigeios, and not on the stage of the succession of the studied area. The number of chemolithotrophic bacteria, particularly thiobacteria, decreased with the change of the growth phase of C. epigeios. The number of acidophobic thiobacteria depended more on the stage of succession, and the number of acidophilic thiobacteria depended more on the age of the C. epigeios. The number of microorganisms that metabolize nitrogen of organic compounds, oligonitrophilic microorganisms and microorganisms that metabolize nitrogen of inorganic compounds in the samples of tailings from the area with grasses and perennials and from the area with grasses, shrubs, and sun-loving trees was higher, compared to the number of these groups of microorganisms in the control and changed with the change in the growth phase of C. epigeios. The number of microorganisms that metabolize nitrogen of organic compounds, oligonitrophilic microrganisms and microorganisms that metabolize nitrogen of inorganic compounds was the highest in the samples from the area with grasses, shrubs, and sun-loving trees during the adult growth phase of C. epigeios. In the area where C. epigeios dominated within the vegetation, the highest number of microorganisms that metabolize nitrogen of organic compounds was also during the adult phase of C. epigeios, and the number of bacteria that assimilate mineral forms of nitrogen and oligonitrophilic microorganisms was the highest during the sub-adult stage. The index of pedotrophicity is higher in the samples taken in the area where C. epigeios prevails among other herbaceous plants, and where in the tree layer there are Betula pendula, Populus tremula with an admixture of Pinus sylvestris. Pedotrophicity indices which were calculated for these samples do not depend on the growth stage of C. epigeios and are higher than for the control area. Immobilization-mobilization of nitrogen indices in samples of tailings from the area with grasses and perennials and from the area with grasses, shrubs, and sun-loving trees ranged from 1.94 to 3.52 and were higher compared to the control site.