卷 87, 编号 5 (2018)

Human natriuretic peptides (NUPs) types A and C were shown have different effects on the growth of monospecies and binary biofilms of human skin commensal microorganisms Staphylococcus epidermidis and Staphylococcus aureus. The effect of natriuretic peptides depended on cultivation conditions: at 37°С growth of monospecies biofilms formed by S. epidermidis and S. aureus was stimulated and inhibited, respectively, resulting in changed values of the biofilm average thickness and biomass in presence of NUPs. At 33°С effects of NUPs reversed: growth of S. epidermidis monospecies biofilms was inhibited. In binary biofilms at 37°С, NUPs were able to increase the competitiveness of S. epidermidis against S. aureus. NUPs affected predominantly biofilms and, to a lesser degree, planktonic cultures. This phenomenon makes it possible to consider NUPs as the molecules able to regulate the interactions between the human organism and skin microbiota.

The effect of sodium, potassium, magnesium, and aluminum ions, as well as of the chloride ion on the growth and ferrous iron oxidation by moderately thermophilic acidophilic iron-oxidizing microorganisms was studied. Strains of the microorganisms predominant in biohydrometallurgical processes (bacteria of genus Sulfobacillus and archaea of the genus Acidiplasma) were the subjects of the study. Ability of the studied strains to grow and oxidize ferrous iron in the media containing different concentrations of sodium, potassium, magnesium, and aluminum (up to 1000 mM) was determined. The experiments were conducted in two variants, in which the studied metals were added to the medium as sulfates and chlorides, respectively. It was revealed that inhibitory effects of the studied metals on the studied strains differed insignificantly and that high concentrations all studied salts inhibited growth and ferrous iron oxidation. The studied Acidiplasma strains were shown to be more tolerant to the cations than the Sulfobacillus strains. The inhibitory effect of chloride ion on the studied strains was the most significant, which were probably adapted to the habitats characterized by high concentrations of metals and sulfates, but not of chloride ions. The mechanisms of action of the studied light metal ions on growth of iron-oxidizing acidophilic microorganisms are discussed.

Secondary metabolites of 25 Penicillium strains isolated from high-latitude ecosystems (upper layer of Antarctic soils and Arctic permafrost deposits) were analyzed. Out of the studied strains, 80% were found to produce secondary metabolites belonging to benzodiazepine alkaloids (anacin, cyclopenin, and cyclopeptin), quinoline alkaloids (viridicatin and 3-methoxyviridicatin), diketopiperazine alkaloids (aurantiamine, 3,12-dihydroroquefortine, roquefortine and rugulosuvin B), polycyclic indole alkaloids (communesin B and chаetoglobosine A), clavine ergot alkaloids (rugulovasins A and B, festuclavine, fumigaclavines A and B, and cyclopiazonic acid), polyketides (mycophenolic acid and citreoviridin), terpenes (andrastins A and B and phomenone), and N-acetyltriptamine. Most strains of the Penicillium subgenus isolated from anthropogenically impaired upper layers of Antarctic deposits and from subsurface Arctic deposits exhibited more complete spectra of secondary metabolites compared to three strains isolated from permafrost 15 000 to 600 000 years old. This is the first report on andrastins formation by a P. restrictum. Wide occurrence of rugulovasins in P. variabile strains was shown.

A facultative methylotroph, strain F5^Т, which uses methylamine and a broad spectrum of polycarbon substrates as carbon and energy sources, was isolated from silt of a freshwater lake in the southern Moscow region. The cells were gram-negative, coccoid, non-spore-forming, nonmotile, colorless, reproducing by binary fission and possessing a capsule. The organism was mesophilic, neutrophilic, not halophilic, oxidase- and catalase-positive, and capable of nitrate reduction to nitrite. Methylamine was oxidized by amine dehydrogenase and via the icl^- serine pathway of С₁ metabolism, as was indicated by activities of hydroxypyruvate reductase and serine-glyoxylate aminotransferase and by the absence of hexulosephosphate synthase and ribulose bisphosphate carboxylase. Predominant fatty acids were C_18:1ω7c (72.3%) and C_16:0 (11.6%). Phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, and phosphatidylethanolamine were the dominant phospholipids. The G + C DNA content was 65.8 mol % (T_m). Q₁₀ was the dominant ubiquinone. Strain F5^T exhibited high similarity of the 16S rRNA gene sequences with Paracoccus strains: P. aminovorans JCM7685^T = VKM B-2140^Т (98.0%), P. huijuniae FLN-7^Т (97.9%), and P. limosus NB88^T (97.5%). However, the level of DNA-DNA relatedness between the strains F5^Т and P. aminovorans^Т was only 21 ± 3%. Based on the data obtained, strain F5^Т was identified as a new Paracoccus species with proposed name Paracoccus simplex sp. nov. (= VKM B-3226^T = CCUG 71989^T).

The structure of microbial mats from the Mramornaya Bay (Crimea) was investigated. Light microscopy in combination with transmission and scanning electron microscopy revealed the base of bacterial mats to be interwoven thin filaments (100 to 500 nm in diameter) consisting mainly of sulfur. Numerous bean-shaped single microbial cells (~1.6 × 0.7 µm), some of which were attached to sulfur filaments, were also revealed. High-throughput sequencing of the 16S rRNA genes revealed predominance of bacteria of the genera Arcobacter (27%), Alcaligenes (17%), and Desulfuromonas (8.5%) as well as of uncultured members of the family Lachnospiraceae (4.9%). No clearly predominant microbial taxa were revealed in the detritus sample below the mats. Similar to the bacterial mat, bacteria of the genera Arcobacter and Desulfuromonas were predominant in the detritus, but their relative abundance was significantly lower (4.1 and 6%, respectively). Analysis of the 16S rRNA gene sequences specific for the genus Arcobacter revealed considerable phylogenetic diversity of this group in the samples from both the upper bacterial mats and the detritus sediment. Most of obtained sequences formed common clusters with the sequences of various uncultured members of the genus Arcobacter, while an insignificant share of them was related to the recently described sulfide-oxidizing bacterium “Candidatus Arcobacter sulfidicus.” Thus, members of the phylogenetically heterogeneous group of epsilonproteobacteria of the genus Arcobacter were the dominant component of the Mramornaya Bay microbial communities.

Hydrocarbon-oxidizing bacteria isolated from soil samples from different climatic zones (Belarus, Libya, Iraq, and Antarctica) were studied. Techniques of physiological, biochemical, and molecular genetic analysis were used to identify 18 strains, most of which belonged to nonmycelial actinomycetes. Informative genetic markers used for identification of bacteria of the genus Rhodococcus were the genes alkB (for R. pyridinivorans), rpoC and groES (for R. erythropolis), groEL (for R. opacus), and random chromosome fragments (for R. opacus and R. pyridinivorans). Bacteria isolated from Libyan sandy soil and Antarctic soil and identified as Dietzia sp. 10-15, Deinococcus sp. А2-6, Alkanindiges sp. A36-1, and Alkanindiges sp. A36-3 exhibited low similarity of their 16S rRNA gene sequences to those of the closely related species and differed from them in a number of physiological and biochemical characteristics, which supported their identification as members of new species. Comparative physiological, biochemical, and fingerprint analysis of the strains belonging to the same species revealed intraspecific polymorphism. Strains capable of growth at high and low temperatures, resistant to UV-irradiation, elevated NaCl concentration, and acidic or alkaline conditions were revealed. This is the first report of oil degradation by R. pyridinivorans 5Ар at elevated temperature (45°C) and by R. erythropolis A2-h2 at 4°C.

Insolubility of chitosan and oligochitosan in aqueous media above pH 6.2–6.5 and the resulting decreased penetration thorough mucosa restricts significantly their application in biomedical compositions. To create non-cytotoxic chitosan derivatives with a high antibacterial activity in weakly alkaline physiological media, alkali-soluble derivatives of oligochitosan and low-molecular weight chitosan were synthesized by coupling a betaine substituent to the nitrogen atom of glucosamine units. Comparative studies of the pH range of the solubility of these derivatives depending on the chain length and modification degree of oligochitosan with M_w = 9.7 ± 1.7 kDa were carried out. It was found that 12 mol % of betaine substituents was the optimal modification degree ensuring the existence of a single-phase solution of modified oligochitosan (M_w = 2–10 kDa) within the entire pH range. Investigation of the antibacterial activity of betaine derivatives against gram-positive (S. aureus) and gram-negative (E. coli) bacteria revealed their high antibacterial effect in both weakly acidic and weakly alkaline environments. Betaine derivatives were found to be nottoxic towards cow lung epithelial cells (LEC) at concentrations below 2.5 mg/mL. The results obtained seem promising for the application of these derivatives in biomedical compositions.

The effect of chitosan (200 kD, 75% deacetylation) on Nosema apis development in bee colonies during wintering was investigated. The conditions for development of the nosematous infection were analyzed. According to the results of determination of PCR products specific for N. apis, chitosan decreased significantly the degree of infection of individual bees with N. apis spores. The scheme of stimulation of the bee immune system by chitosan via the changes in the level of antimicrobial peptides and proteins of the macroorganism antioxidant systems is discussed. Due to a decrease in the degree of infection with N. apis, survival of the bees increased during the long winter period.

The mini-review deals with the recent developments in investigation and application of chitosan and its derivatives within a broad range of human activities. A short historical note on discovery of chitin and chitosan is provided. Special attention is paid to chitosan occurrence and structure, as well as to antimicrobial properties of this biopolymer and their dependence upon the physicochemical characteristics of chitosan: its molecular mass and deacetylation degree, and the conditions of derivative formation. The possible mechanisms of chitosan biological activity are briefly considered.