Microbiology

The review presents the key results of the study of biosilica obtained from diatoms and its application in various fields of science and technology. The purpose of this review is to systematize data on the properties, modification methods and areas of application of this material. The data on the properties of biosilica are summarized and the main modification methods are considered, which can significantly expand the range of functional characteristics of this material. Particular attention is paid to the use of unmodified and modified biosilica in biomedicine as nanocouriers of drugs, materials for tissue regeneration, treatment of infected wounds, as well as biosensors and matrices for SERS analysis. Data on its effectiveness in environmental studies, such as wastewater treatment from heavy metals, organic dyes and phenols, are presented. New promising areas of application of biosilica are separately considered, including its use in energy, chromatographic analysis and other innovative areas. The review summarizes modern data and emphasizes the importance of developing new modification methods to expand the functionality of this unique material.

In August 2023, studies of microbial communities in the water column of a cascade of high-mountain lakes in the Western Caucasus (Lake Klukhorskoye) were conducted. Data on the composition of microbial communities and the biogeochemical activity of microbial processes were obtained and analyzed. The lakes of the cascade (Bolshoye, Maloye and Vostochnoye Klukhorskie) are located at an altitude of 2670–2980 m and are ultra-fresh and oligotrophic, similar in hydrochemical composition, but differing in temperature and water transparency. The value of primary photosynthesis production was 5.3–8.0 μg C l^–1 day^–1, dark carbon dioxide assimilation 0.5–1.2 μg C l^–1 day^–1. The values of the total number of microorganisms varied from 70 to 150 thousand cells ml^–1. In the oligotrophic waters of the Klukhor Lakes, the bacterial phyla Actinobacteriota, Bacteroidota, and Pseudomonadota, representing mainly aerobic heterotrophic groups, dominated in the microbial community. Archaea constituted less than 1% of the community. Microorganisms that are indicators of turbid and transparent waters of the studied lakes were identified. These are aerobic Gram-positive bacteria of the Ilumatobacteraceae family, psychrophilic bacteria of the Comamonadaceae family – important components of glacial microbiomes, and oligotrophic bacteria of the Sphingomonadaceae family, resistant to solar radiation, including ultraviolet radiation. The microalgae community of the water column of Lake Bolshoe Klukhorskoye included representatives of green microalgae, diatoms Pinnularia, chrysomonads, and cryptophytes. The composition of microalgae in the three lakes differed significantly. The cyanobacteria of the transparent Maloye Klukhorskoye Lake were poorer than those of the Bolshoe Klukhorskoye Lake. In the Bolshoe Klukhorskoye Lake, copepods Centropages sp. and Acanthodiaptomus denticornis, adapted to extreme high-mountain conditions, including low temperatures and high ultraviolet radiation, were found in the water column. The results of the work indicate that the formation of new periglacial lakes and the loss of connection with glaciers during their retreat leads to a change in the structure of plankton communities during the transition from turbid glacial lakes to transparent ones. The composition of microbial communities of water bodies and their biogeochemical productivity can be indicators of large-scale and local climate change.

A new sulfate-reducing strain SRJS8^T with a high capacity to biodegradate petroleum hydrocarbons has been isolated from the bottom sediments of the northern part of the Sea of Japan. The cells were gram-positive, single-spore-forming motile rods 0.4–0.5 × 2.0–5.0 µm in size. Strain SRJS8^T grew at the temperature range from 6°C to 30°C (optimum at 25°C), pH 6.3–7.7 (optimum 7.3), and NaCl concentrations ranging from 0 to 20g/L (optimum 2 g/L). Strain SRJS8^T used butanol, glycerol, methanol, ethanol, butyrate, lactate, pyruvate, formate, yeast extract, H₂/CO₂, crude oil as electron donors and carbon source in the presence of sulfate. SRJS8^T used sulfate, sulfite, thiosulphate, elemental sulphur, fumarate and Fe(III) as electron acceptors with lactate presence. The closest relative of the SRJS8^T was Desulfosporosinus lacus STP12^T with 98.49% similarity. The complete genome of strain SRJS8^T (5.43 Mb) was sequenced. DNA–DNA homology of the SRJS8^T and D. lacus was 57.4%, and the ANI value was 93.69%. The genomic DNA G + C content was 42.08%. In accordance to the obtained data, SRJS8^T is a novel species within the Desulfosporosinus genus, for which the name Desulfosporosinus shakirovi sp. noV. is proposed. The type strain is SRJS8^T (= VKM B-3489^T, = JCM 39189^T).

Biofilm formation has equal adaptive significance for both epiphytic and endophytic rhizobacteria due to their primary localization on the surface of plant roots. The typical strains Azospirillum brasilense Sp7 and A. baldaniorum Sp245 formed biofilms in the root system of wheat (Triticum aestivum L.) mainly in the zones of the root apex and root hairs, as well as in the places of formation of lateral roots. In the case of the strain Enterobacter cloacae K7 isolated from the roots of Jerusalem artichoke (Helianthus tuberosus L.), biofilm formation in certain root zones was not a characteristic feature. Strain K7 colonized the roots, forming biofilms on the surface of the conduction, absorption, and root tip zones. The strains Sp7/Sp245 and K7 were not antagonists, and in the population of their mixed biofilms (studied on the Sp7 and K7 model), the proportions of subpopulations of each strain were approximately the same. However, in the root system of seedlings inoculated with mixed cultures of K7 and Sp7/Sp245, there were areas in the biofilms in which multicellular clusters of one strain were isolated from the cluster of bacteria of the other. Diffuse distribution of Sp7/Sp245 cells among enterobacteria or K7 cells between azospirillum was not typical.