Microbiology

The review analyzes current information on the processes of formation of microbial biofilms, both fixed on biotic and abiotic surfaces, and arising as a result of autoaggregation and coaggregation in the thickness of the liquid. The physicochemical phenomena occurring during recognition of the phase boundary surface by microorganism cells are described in detail. The components of the extracellular polymer matrix of biofilms, the regulation of their formation, the structural significance for the architecture of biofilms and the protective role when exposed to biocides (including antibiotics) and other adverse environmental factors are described in detail. Approaches to managing the formation of microbial biofilms are considered. A new scheme for the formation of microbial biofilms proposed in the literature, including three stages instead of five, is analyzed.

The efficiency of cryopreservation of cyanobacteria and eukaryotic microalgae of different taxonomic groups, including charophyte, chlorophyte and ochrophyte microalgae, was assessed using 24 strains of the algological part of the All-Russian Collection of Microorganisms (VKM) as an example. Microalgae cultures differing in cell size, morphological organization of the thallus, reproduction method, presence and size of mucous membranes, and ability to form dormant cells were selected for comparative study. Two types of cryoprotectors (methanol and dimethyl sulfoxide), two types of nutrient media (slant agar and liquid medium), and three methods for determining the survival of microalgae after cryopreservation were tested. It was shown that a two-step cryopreservation protocol using both cryoprotectants (methanol and dimethyl sulfoxide) was successfully applied to all 24 studied strains, regardless of their taxonomic affiliation and morphological features. Based on the results of the experiment, a standard operating procedure for cryopreservation of microalgae was developed, including a liquid culture medium with dimethyl sulfoxide, as well as two methods for determining the survival of microalgae after cryopreservation – growth in a liquid medium and streaks on agar. The proposed protocol not only ensures the preservation of cell viability and the possibility of further use of the strain as a morphologically and genetically representative sample, but also minimizes time and resource costs, as well as the risk of contamination of cultures.

We have mapped RNA‒DNA hybrids in the prokaryotic genome for the first time. Using the S9.6 antibody immunoprecipitation method (S9.6-DRIP) followed by whole-genome sequencing, we identified 219 unique peaks of RNA‒DNA hybrids in the genome of Escherichia coli TOP10. These peaks corresponded to 219 different genes and were predominantly distributed in the coding regions of the genome (88.12%). Analysis of individual genes containing RNA‒DNA hybrids revealed that they encode enzymes involved in important energy and metabolic processes in prokaryotes, such as lipoic acid synthesis.