Volume 92, Nº 1 (2023)

Abstract—Microscopic fungi form and excrete numerous and diverse secondary metabolites, including pigments of various colors, which may be used as an alternative to chemical and plant colorants used in industry. Azaphilone compounds, first discovered in fungi of the genus Monascus, are among the promising classes of fungal pigments. The review analyzes the publications on formation of azaphilone-type pigments in Monascus fungi, as well as in Talaromyces and Aspergillus сavernicola. Brief information is provided concerning the antimicrobial, antitumor, anti-inflammatory, and hypolipidemic activities of azaphilone pigments. is given. Possible strategies for increasing the efficiency of the production process and directed synthesis of yellow, orange, and red pigments and their derivatives are discussed. In general, the review provides for assessment of the role of azaphilone pigments, as well as of the prospects and ways to expand their production for use as natural dyes in various fields.

Abstract—An alkaliphilic, facultatively anaerobic bacterium (strain T05b^T) was isolated from a terrestrial mud volcano on the Taman Peninsula, Russia. The cells of the isolate were motile spirilla 0.5 µm thick and 1.5–2.5 µm long. Strain T05b^T grew at 6–42°C (optimum at 30°C), pH 8.0–11.0 (optimum at 9.0), and 0–14% NaCl (wt/vol). Lactate, formate, malate, pyruvate, H₂, elemental sulfur, sulfite, thiosulfate, and sulfide were used as electron donors; nitrate, fumarate, elemental sulfur, sulfite, thiosulfate, dimethyl sulfoxide, arsenate, and oxygen could be used as electron acceptors. Nitrate was reduced to ammonium. Malate, pyruvate, and fumarate were fermented. Microaerobic growth was possible at up to 3% О₂ (vol/vol). Strain T05b^T did not use sulfate and Fe(III) as electron acceptors, was unable of elemental sulfur, sulfite, or thiosulfate disproportionation, and did not ferment glucose, fructose, sucrose, lactate, formate, maleate, yeast extract, or peptone. The predominant fatty acids were C16:1 ω7 (45.9%), C16:0 (25.8%), and C18:1 ω7 (20.9%). The genome of strain T05b^T was 2.46 Mb in size and had the G + C DNA content of 45.5%. It contained the genes encoding the following enzymes of energy metabolism: Nap nitrate reductase periplasmic complex, Phs/Psr thiosulfate/polysulfide reductase, Sqr sulfide:quinone oxidoreductase, and Arr respiratory arsenate reductase. Ac-cording to analysis of the 16S rRNA gene nucleotide sequence, strain T05b^T exhibited 98.61% similarity to the type strain of Sulfurospirillum alkalitolerans (phylum “Campylobacterota”). Based on its phenotypic characteristics and the results of phylogenetic analysis, assignment of the isolate to a new Sulfurospirillum species, Sulfurospirillum tamanensis sp. nov., is proposed, with the type strain T05b^T (=DSM 112596^T = VKM B-3538^T).

Abstract—The biochemical composition of Arthrospira (Spirulina) platensis (Nordstedt) Gomont after long-term storage in the state of anhydrobiosis (4 years, 17 years) was determined by the standard methods. It was shown that protein content (55.3–61.2%) and total carbohydrates content (13.0–15.6%) in cyanobacterial cells were in agreement with the data known from the literature and with our results obtained at the onset of storage. The biomass had low content of free nucleotides (1.8–2.6%), lipids (1.3–11.0%), and especially pigments (0.5–1.3, 0.03–0.12, 1.4–2.0, 0.03–0.05% for chlorophyll a, carotenoids, C-phycocyanin, and allophycocyanin, respectively). The content of nucleic acids content was 3.1–24.0 and 0.11–0.16% for RNA and DNA, respectively. Microscopic examination of A. platensis (17 years of storage) showed high numbers of irreversibly damaged and dead cells (34.2 and 65.8%, respectively). To determine the quantitative and morphological parameters of associated microflora, a complex physicochemical treatment (methanol, ultrasound, and centrifugation) of the reactivated cyanobacterial suspension proved the most efficient. Three main groups were distinguished in the morphological structure of the microbiome (rod-shaped, rounded, and convoluted forms). The community was dominated by rod-shaped forms: large and small rods accounted for 60.5 and 14.4%, respectively. Mycelial forms (thin filaments), cocci, and convoluted forms were less common. On average, the volume of a bacterial cell was 0.27 ± 0.04 µm³. The contribution of bacteria to the biomass of A. platensis varied from 3.3 to 11.3% (8.3 ± 4.4% on average) of the dry weight of A. platensis. It has been suggested that the biochemical parameters and viability of cyanobacteria were affected by the accompanying microflora.

Abstract—The goal of the study was to investigate the mechanism of quorum sensing (QS) inhibition in the model bacterium Chromobacterium subtsugae 026 (previously – C. violaceum 026) by Eucalyptus viminalis Labill leaf extract, and to identify the plant-derived components that provide this biological activity. The raw extract showed pronounced anti-QS activity within a broad concentrations range which were an order of magnitude lower than required for bacterial growth suppression (the MIC₅₀/EC₅₀ ratio of 43.6). Chemical analysis of the extract revealed six small plant-derived molecules: pyrogallol, 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-1, p-cymene, 4-((1E)-3-hydroxy-1-propenyl)-2-methoxyphenol, gallic and palmitic acids, whose inhibitory effect on QS in Chromobacterium spp. has previously been shown by in vitro experiments or predicted by in silico models. In addition, minor components γ-caprolactone and γ-octanolactone, structurally similar to acylated homoserine lactones, QS autoinducers in Chromobacterium spp., were found in the extract. Chemically synthesized analogs of these molecules showed anti-QS activity in the C. subtsugae 026 bioassay (ЕС₅₀ = 354.2 and 145.6 µg/mL, respectively). Enrichment of the E. viminalis leaf extract with γ-caprolactone or γ-octanolactone significantly increased the anti-QS activity of these compositions, which was determined by isobolographic analysis as additive or superadditive effects.

Abstract—The biological activity of chitosan asparaginate particles formed in the chitosan‒L-aspartic acid‒water system at the initial stage of phase separation was investigated. Cultivation of Staphylococcus aureus 209 P and Escherichia coli 113-13 in the medium supplemented with nanoparticles resulted in massive death of bacterial cultures. The biocidal activity against gram-positive bacteria was most pronounced. Biological tests revealed high biocompatibility of chitosan nanoparticles and their ability to accelerate the proliferative activity of the cultures of epidermal and epithelial cells. Our results indicate that chitosan asparaginate nanoparticles are promising for medico-biological and pharmaceutical applications.

Abstract—The most advantageous characteristic of the materials made of synthetic polymers, such as their resistance to biodegradation, is simultaneously the reason for their accumulation and environmental pollution. Nevertheless, some type of plastics under aerobic conditions undergo slow microbial degradation, however, there is lack of information on the anaerobic degradation of plastics. In this work, we studied the growth of anaerobic moderately thermophilic (55°C) consortiums in the presence of samples made of polypropylene (PP) and polyvinyl chloride (PVC). It was shown that the microbial biomass increased compared to the control, as well as anaerobic decomposition products (CO₂, H₂, and H₂S) were detected, and the total weight of the plastics decreased by 4.4% (PP) and 6.5% (PVC) compared to the control. Bacterial cells adhere and form colonies and biofilms on the surface of the plastic materials. An analysis of the composition of microbial communities showed an increased number of anaerobic hydrolytics of the genus Tepidimicrobium, potential syntrophic bacteria of the genus Tepidanaerobacter, and especially sulfate-reducing bacteria (Desulfohalotomaculum). With help of differential scanning calorimetry and Fourier spectroscopy it was revealed that the decrease in the mass of plastic mainly occurred due to the hydrolysis of additives (plasticizers). The role of such microbial communities in the aquatic environment and anaerobic layers of the municipal solid waste landfills, where PP and PVC plastics can be destructed under the elevated temperatures of anaerobic conditions, is discussed.

Abstract—Comparative phylogenetic analysis of NAD⁺-dependent formate dehydrogenases (NAD⁺–FDH) genes, which have been detected in all available genomes of methylotrophs of the genera Ancylobacter, Starkeya and Angulomicrobium, as well as in other members of the family Xanthobacteraceae (Xanthobacter, Aquabacter, Azorhizobium), was carried out. The position of Xanthobacteraceae on the tree constructed based on comparison of NAD⁺–FDH amino acid sequences was found to correlate with the 16S rRNA gene-based phylogeny. The sequences of the NAD⁺–FDH proteins of the genera Ancylobacter, Starkeya, and Angulomicrobium exhibited 87.8–98.3% identity, indicating that this protein is very conservative within this group of methylotrophs. For the first time, analysis of the NAD⁺–FDH functional genes is recommended as a supplementary criterion for interspecies differentiation between methylotrophic bacteria of the genus Ancylobacter.