Volume 93, Nº 5 (2024)

Until mid-1970s, cyanobacteria have been interpreted as algae despite they differed from other members of this taxonomic group by the absence of cell nucleus (that is currently considered a character of prokaryotic organization). However, when bacteria were reinterpreted as prokaryotes, blue-green algae became reattributed as cyanobacteria, and bacteriologists began to study their cultured strains with microbiology methods. But since these objects did not obey the provisions of bacteriological code (ICNB), the development of their taxonomy had certain problems, especially regarding nomenclature, that could not be solved until early-2010s. Current changes in taxonomy of cyanobacteria result from a general progress in taxonomy of prokaryotes due to the explosive accumulation of 16S rRNA gene sequencing data, particularly of uncultured objects. Advances in the description of cyanobactera are as follows: I) based on polyphasic approach, new taxa ranging from species to order were published; II) “dark” objects demonstrating several types of non-photosynthetic metabolism were described; III) the objects producing red-shifted chlorophylls d and f were published. Advances in the nomenclature of cyanobacteria are: IV) taxa validly published according to the botanical code (ICN) are also considered valid under the prokaryotic code (ICNP); V) category of phylum was introduced into ICNP, and due to valid publication of the type genus Cyanobacterium, the phylum name Cyanobacteriota became legitimate; VI) names of uncultured Candidatus objects could get standing in nomenclature based on the SeqCode in which type material is represented by genomic DNA sequences. Advances in the classification of cyanobacteria are: VII) evolutionary tree of oxygenic phototrophs and related phylotypes was construed; VIII) phylogenomic system of orders and families was elaborated; IX) ecogenomic system combining genome analysis and genome distribution data was offered. The subject for future research is a restriction of taxonomic redundancy in cyanobacteria, and further attempts to develop their species concept.

Culture of cyanobacteria “Anabaena” sp. isolated from alluvial meadow soils in the south of Russia and deposited in the collection of cultures of microalgae and cyanobacteria IPPAS of the Institute of Plant Physiology named after. K.A. Timiryazev RAS under the number IPPAS B-2020. Phylogenetic analysis showed that the studied strain belongs to a clade that unites the genera Sphaerospermopsis, Amphiheterocytum, Raphidiopsis, Wollea and Neowollea, but cannot currently be assigned to any of them. The phytotoxicity, fungicidal and antioxidant activities of the strain were studied. The culture turned out to be non-toxic. Water-alcohol extract and biomass of “Anabaena” sp. IPPAS B-2020 had a complete suppression of micromycetes Fusarium culmorum, Fusarium graminearum, Fusarium sporotrichioides with a maximum diameter of the growth inhibition zone of 2.5 cm. The water extract of cyanobacteria “Anabaena” sp. had pronounced antioxidant activity. IPPAS B-2020 in the amount of 20 µl – 39.3%. As part of the metabolites of “Anabaena” sp. IPPAS B-2020 detected organic acids (citric, lactic, acetic), terpenes, alkanes, alcohols and other low molecular weight organic compounds. Culture “Anabaena” sp. IPPAS B-2020 is of interest for biotechnology as a producer of such important biologically active compounds as tributyl phosphate, D-limonene, squalene, α-pinene.

The diversity of microbial communities and potential functional activity in anaerobic processes of oil degradation of bottom sediments was determined in the area of the Bolshaya Zelenovskaya oil seepage site (lake Baikal). When microorganisms of subsurface and deep sediment were cultivated in enrichment cultures containing oil and various electron acceptors for one year at 10ºC, the concentration of n-alkanes decreased by 1.2–2 times, and PAHs by 2.2–2.8 times. The conversion of hydrocarbons was accompanied by the generation of hydrocarbon gases (methane, ethane). The microbial community of the subsurface sediment was characterized by greater bacterial diversity than that of the deep sediment and was represented by microorganisms specialized in the decomposition of a wide range of substrates, including petroleum hydrocarbons. The deep layers of sediment were dominated by Atribacterota, Caldisericota and Bathyarchaeia (Thermoproteota), as well as representatives of the “rare biosphere” Elusimicrobiota and Candidatus Hadarchaeota. Among the main participants in the degradation of oil in bottom sediments of the lake. Representatives of the phyla Bacillota, Pseudomonadota, Chloroflexota, Actinomycetota, Desulfobacterota, Atribacterota, Halobacteriota and Bathyarchaeia (Thermoproteota) can be classified as Baikal.

Increasing plastic pollution is a serious environmental problem as widespread production and inadequate disposal of plastic materials lead to adverse impacts on ecosystems. The research investigated the structural and functional features of the anaerobic microbial community in contact with waste from extruded polystyrene (XPS) under methanogenic (MG), nitrate-(NR) and sulfate-reducing (SR) conditions. It has been shown that the presence of XPS in the microbial community does not have a negative effect on the processes of biogas formation, but, on the contrary, leads to an increase in the yield of methane and volatile fatty acids and a change in their ratio. Microparticles of different sizes were found in the culture fluid of variants with XPS: in NR conditions ‒ 2.4 × 10⁶/ml, in SR conditions ‒ 1.2 × 10⁶/ml and in MG conditions ‒ 0.4 × 10⁶/ml, while in control variants microparticles was not found. Using scanning electron microscopy, it was revealed that in all experimental variants the surface of the polymer became looser, more textured, and irregularities, cracks and holes appeared. Increased diversity in the microbial community, associated with an increase in the number of microbial morphotypes, correlates with the results of high-throughput sequencing of the 16S rRNA gene. When XPS was introduced into an anaerobic community incubated in different donor-acceptor conditions, the number of groups of microorganisms included in it increased and the proportion of representatives of hydrolytic and acidogenic bacteria (Sedimentibacter, Lentimicrobium), acetogenic syntrophs (Syntrophomonas, Desulfovibrio, Geobacter) and methanogenic archaea (Methanosarcina, Methanobacterium) increased. Our study shows that waste from XPS is not inert for the microbial community and contact with it leads to significant changes in its structure and functioning. However, since the experiments were carried out using household XPS containing various fillers in addition to the main polymer, there is a possibility that, along with polystyrene, additional substances included in its composition (plasticizers, dyes, etc.) are also subject to degradation. The ability of microorganisms to destroy the polymer itself requires further research.

Phosphate transporters in yeast cells are responsible for phosphorus homeostasis, and also indirectly involved in the regulation of various adaptive processes. One of these processes is the adaptation to ethanol consumption, which requires significant changes in phosphorus metabolism. We demonstrated that knockout mutations in the genes encoding phosphate transporters PHO87, PHO89, PHO90 and PHO91 impair adaptation of Saccharomyces cerevisiae to ethanol consumption at ethanol concentration of 4%. For these mutant strains an extension of the lag phase and in a decrease in the growth rate at the active stage was observed when the cells were cultivated in the medium with 4% ethanol. Mutant cells differ in the content of inorganic polyphosphates, but not orthophosphate, from the parental strain: they contain less long-chain polyphosphates when cultivated on ethanol, but not on glucose. When cultivated on a medium containing 4% ethanol, a strain with a knockout mutation in the PHO84 gene, encoding the transporter of phosphate and divalent metals, as well as knockout strains for the PHM6 and PHM7 genes, responsible for the polyphosphate overplus, did not show any growth differences compared with parent strain in a medium with 4% ethanol. The possible role of phosphate transporters and inorganic polyphosphates in the adaptation of yeast to ethanol consumption is discussed.

Using restriction analysis of the 5.8S-ITS rDNA fragment and sequencing of the D1/D2 domain of 26S rDNA, the yeast microflora of various dairy products sold in Russia was studied. Most of the fermented milk products studied were dominated by lactose-utilizing yeasts Kluyveromyces and Debaryomyces, as well as lactose-negative yeasts Saccharomyces, Monosporozyma, Pichia, Geotrichum and Yarrowia. The yeast Kluyveromyces marxianus was present in most of the fermented milk products studied, while the related species K. lactis was found only in some samples of ayran, curds and cheese. The dominance of K. marxianus is apparently associated with their physiological characteristics (thermo- and osmotolerance), which provide these yeasts with better adaptation to industrial fermentation conditions. The dominant species in mixed-fermentation dairy products, Saccharomyces cerevisiae and Monosporozyma unispora, were completely absent in cheeses and lactic acid fermentation products. In general, the species composition of yeasts largely depended on the fermented milk product, the type of milk and the specific manufacturer.

In a sequentially periodic bioreactor, changes in the structure and properties of a community enriched with phosphate-accumulating microorganisms (PAO) after a shift in pH to more acidic values (pH 6.7–7.1) were traced. The proportion of Candidatus Accumulibacter decreased from 43.6 to 13.9%, while the number of potential FAOs belonging to Dechloromonas and Thauera increased. At the same time, the share of the total amount of FAO changed slightly and amounted to 40–43%. The share of the main competitors of FAO ‒ glycogen-accumulating microorganisms (GAM) during the experiment remained insignificant: Competibacter 16S rRNA gene fragments before and after pH changes amounted to 2‒4%. A decrease in pH led to a drop in the amount of phosphates released in the anaerobic phase, but the amount of phosphorus in the biomass and its removal remained high ‒ 15–17 and 92–94%, respectively.

The adaptive proliferation of bacteria or cell division in the absence of an exogenous organic substrate is controlled by density-dependent mechanisms with the participation of AHL- and AI-2-dependent quorum sensing systems. Along with the signaling molecules of these bacterial communication systems, bacterial metabolites that are permanently released during microbial metabolism, for example, CO₂, can also participate in regulation and can serve as biomarkers of cell density. It has been established that carbon dioxide is necessary for the adaptive proliferation launch, and the increased content of atmospheric CO₂ causes a premature stop to this process. Thus, CO₂ is able to regulate the adaptive reactions of bacteria, including, probably, being one of the signals involved in the initiation and termination of the process of adaptive proliferation. It has been shown that CO₂ in the form of the bicarbonate ion HCO₃^- can activate the cAMP-dependent signaling cascade and is also included in the bacterial cell mass.

A technology has been developed for producing a probiotic preparation by solid-state cultivation of a mixed culture of Bacillus subtilis B-8130, B. subtilis B-2984, B. subtilis B-4099 on beet pulp, which is shown in two preparations (ProStor and GerbaStor). Solid-state fermentation was carried out under conditions of limited access to oxygen at a temperature of 40 ± 5°C, pH 7.5‒8.0 and mixture humidity 45 ± 3% for 48‒50 hours. During the process, acidification of the reaction mass was observed, a significant increase in cell titer and the formation of a biofilm on phytosorbent. The cell titer depended on the factor “stage of fermentation”, but did not depend on the factor type of preparation ‒ ProStor or GerbaStor. Among the identified volatile products, by 48 hours of fermentation the content of acetic acid, 3-methylbutanoic acid, p-guaiacol and 2-n-pentylfuran increased, and aromatic substances of the phenolic series decreased. Additional metabolites were obtained that enhance the antibacterial properties and taste of the probiotic preparation. The formation of a biofilm made it possible to preserve viable cells during drying (45°C): in ProStor 1.2 × 10⁸ CFU/g, and in GerbaStor 0.58 × 10⁸ CFU/g. In HerbaStore with an expanded range of medicinal plants, a decrease in the titer of bacilli is associated with dehydration during drying and with the antibacterial properties of phytocomponents.