Vol 87, No 2 (2018)

The microorganisms forming symbioses with insects play an important role in nutrition, development and evolution of their hosts. They make it possible for their hosts to use poorly digestible nutrients, to resist the biotic and abiotic stresses, and to regulate the metamorphosis. The microsymbionts of insects may be facultative (genetically specialized for symbiosis but retaining the capacity for autonomous existence; they are usually located extracellularly, in the gut, hemolymph, or salivary glands of the host) or obligatory (incapable of autonomous existence due to the loss of large parts of their genomes; they are usually located inside specialized host cells). The intracellular symbionts (endocytobionts) are capable of vertical transmission during the host reproduction, which determines the loss of many housekeeping genes, including the genes for replication, transcription and translation. In some obligatory symbionts, amplification of genes performing the functions useful for the hosts, such as the synthesis of essential amino acids, was found. These symbionts exhibit increased rates of accumulation of mutations, including non-synonymous nucleotide substitutions, reflecting suppression of the purifying selection and activation of genetic drift stimulating the genome reduction. Transfer of some genes from endocytobionts to the nuclear chromosomes of insects enables them to implement the novel metabolic functions, including assimilation of rare nutrients. The obligatory intracellular insect symbionts may be used as models to reconstruct the early stages of evolution of cellular organelles, which involve reduction of essential genes and the loss of genetic individuality of the symbionts, i.e., the ability for self-maintenance and expression of their residual genomes. Genetic analysis of insect microsymbionts extends the opportunities for their practical application associated with biological control of harmful insects (herbivorous, bloodsucking) and stimulation of the beneficial ones (honey collectors, pollinators, antagonists of pests).

Ability to reduce insoluble Fe(III) compounds has not been shown for alkaliphilic lithotrophic sulfate and sulfur reducers. Detection of this metabolic process in sulfidogenic prokaryotes could significantly expand the present knowledge on physicochemical range of their growth and physiological activity, which is now limited by low negative ambient redox potential. Capacity for direct reduction of Fe(III) from chemically synthesized ferrihydrite was tested for eight species of hydrogenotrophic haloalkaliphilic sulfidogens grown with formate or H2 as electron donors in the absence of sulfur compounds in the medium. Out of eight tested species, six reduced iron with formate and five, with hydrogen as the electron donor. Iron reduction correlated with stimulation of growth on formate or hydrogen only in two sulfidogenic species. Analysis of available genomes of five tested species revealed that only Dethiobacter alkaliphilus and Desulfuribacillus alkaliarsenatis possess the gene sets of multiheme cytochromes c required for typical dissimilatory iron reduction. The presence of these genes in two strains with high iron-reducing activity indicates the capacity of some haloalkaliphilic sulfidogenic bacteria for carrying out direct dissimilatory reduction of insoluble Fe(III) forms in the absence of sulfur-containing electron acceptors, i.e., without using sulfide as a soluble mediator of iron reduction. In other studied microorganisms, the ability to reduce iron is probably caused by nonspecific metabolic activity and is not directly linked to energy generation for growth, although the rates of Fe(III) reduction determined in our experiments make it possible to suggest significant role of sulfidogenic microorganisms (normally reducing sulfur and sulfate) in the iron cycle in haloalkaline ecosystems upon decreased content of sulfur compounds.

Unlike the wild type, the mutant Aspergillus carbonarius synthesized a yellow pigment, partially saturated canthaxanthin (PSC) when the growth medium acidified to low pH. Since the pigment found pharmaceutical applications, the possible mechanism involved in its ability to grow at extreme acidic conditions is described. To understand the mutation in the pathway, specific inhibitors affecting carotenoid biosynthesis were used in the medium and PSC synthesis and cell integrity were studied. Results suggested that the possible occurrence of mutation in the isoprenoid pathway for higher production of carotenoid as well as ergosterol caused the mutant to grow in extremely acidic conditions. The results also suggested that the flow of carbon for sterol biosynthesis and that of carotenoids are dependent. The deposition of carotenoids and ergosterol in the cell membrane causing the cells to maintain pH homeostasis under the acidic growth conditions is of significant importance. In A. carbonarius, understanding the cause of stress induced PSC accumulation is essential for efficient expression and production of the pharmaceutically significant carotenoid and this will further facilitate research into the role of carotenoids in stress tolerance of other filamentous fungi.

Soil, enodphytic, and insect-pathogenic micromycetes of the genus Beauveria are widespread in nature and are important producers on mycoinsecticides, enzymes, and pharmacologically usable and toxic compounds. The goal of the work was to determine chemodiagnostic approaches to differentiation of Beauveria cryptic species using the strains B. bassiana BBL and B. pseudobassiana BCu22 by comparing their toxicological properties (insecticidal, antimicrobial, phytotoxic, cytotoxic, and esterase-inhibition activity) and metabolite profiles (TLC and HPLC/DAD patterns) of the extracts from the cultures of these fungi growing on different loose substrates, on solid and liquid media. It was shown that when the strains were cultured in liquid media (SDAY and Adámek medium) and on solid substrates (millet and Czapek agar medium), they could be differentiated by the extract yield and chromatographic profiles, as well as by their insecticidal, antifungal, and cytotoxic activity. Thus, antifungal properties were more pronounced in B. pseudobassiana BCu22 grown in liquid Adámek and SDAY media, while cytotoxic properties were more notable in B. bassiana BBL grown in Adámek medium and on millet. Insecticidal properties of the extracts from these cultures varied depending on the substrate composition. Since the extracts of the studied fungi exhibited a broad spectrum of biological activity, the toxic properties of Beauveria spp. should be considered in the course of assessment of safety of these fungi as bioinsecticides.

Herein, we reveal the alteration in phenol oxidase enzymes complex production from Azospirillum brasilense Sp245 omegon mutants with polar and lateral flagella dysfunction and from A. brasilense Sp7 phase variants with different plasmid composition. The enzymatic activities for various laccases, tyrosinases, Mnperoxidases, and lignin peroxidases as well as the isomorphic composition of intracellular laccases and tyrosinases were estimated for the studied variants and the parent strains. It was noted that various genetic events correlating with phenotypic heterogeneity in A. brasilense populations affect their phenol oxidase activity level.

Geochemical, biogeochemical, and molecular genetic investigation of the upper (0–5 cm) bottom sediments of the Yamal sector of the Kara Sea was carried out. The Yamal sector is well-protected from the massive inflow of river water. The sediments were oxidized at the surface and weakly reduced in the 3−5-cm layer. C_org content varied from 0.1 to 1.3%, while the level of dissolved СН₄ was 1.9 to 20.3 μmol L^–1. The isotopic composition of organic matter (OM) carbon, δ¹³Corg, varied from–27.5 to–22.2‰ (–25.4‰ on average). The share of terrigenous OM was 13.3 to 72.2% (48.9% on average). The rate of methane production, methane oxidation, and sulfate reduction varied from 0.8 to 9.0 (2.7 on average) nmol СН₄ dm^–3 day^–1, from 9.9 to 103 (31.6 on average) nmol СН₄ dm^–3 day^–1, and from 0.49 to 2.2 (1.1 on average) μmol S dm–3 day–1, respectively. High-throughput sequencing of the amplicons of the 16S rRNA genes was used to reveal the physiological groups of microorganisms responsible for the processes of methane production and oxidation, sulfate reduction, and oxidation of reduced sulfur compounds. Members of the phylum Woesearchaeota were predominant among archaea. Methanogenic archaea belonged to the families Methanobacteriaceae, Methanococcaceae, and Methanosarcinaceae (Euryarchaeota). Methanotrophs of the family Methylococcaceae were revealed among the Gammaproteobacteria, with their share in the sediments ~1%. In the class Deltaproteobacteria (15.4%), three orders of sulfate reducers were predominant: Desulfobacterales, Desulfovibrionales, and Desulfuromonadales. Oxidation of reduced sulfur compounds was carried out by chemolithoautotrophic bacteria of the genera Sulfurovum, Sulfurimonas, and Arcobacter of the class Epsilonproteobacteria (1.1% of the total microbial number).

Diversity of the oil-degrading microbial strains isolated from the water and sediments of the Gulf of Finland (Baltic Sea) in winter and in summer was studied. Substrate specificity of the isolates for aliphatic and aromatic hydrocarbons was studied. The isolates belonged to 32 genera of the types Proteobacteria (alpha-, beta-, and gammaproteobacteria), Actinobacteria,Firmicutes, and Bacteroidetes. Seasonal variations of the oil-degrading microbial communities was revealed. The presence of the known genes responsible for the degradation of oil aliphatic and aromatic hydrocarbons was determined. The alkB sequence of the alkane hydroxylase gene was found in ~16% of the studied strains. The sequence of the phnAc phenanthrene 3,4- dioxygenase was found in Sphingobacterium sp. and Arthrobacter sp. isolates retrieved in winter and summer. In five Pseudomonas sp. strains from winter samples, the classical operons of naphthalene degradation (nah) were localized in catabolic plasmids, of which three belonged to IncР-9, one, to IncР-7, and two to an unidentified incompatibility group. Burkholderia and Delftia strains contained the operons for naphthalene degradation via salicylate and gentisate (nag). The presence of nag genes has not been previously reported for Delftia spp. strains. The sequences of the nagG salicylate 5-hydroxylase gene were also found in Achromobacter, Sphingobacterium, and Stenotrophomonas strains.

Along the coastal belt of Makran, on the southeastern margin of Iran, there are several active and inactive mud volcanoes with different morphologies. Ain—an actively bubbling eye-shaped mud pool—is one of these unique geological phenomena. Present study indicates the first overview of the bacterial diversity of this mud volcano obtained by culture techniques. For this purpose, two samples were collected at two different depths of the mud pool and were cultivated on two different nutrient culture media. A total of 13 isolates were randomly chosen for further phenotypic and genotypic characterization. Growth of the isolates occurred at 25–42°C, pH 8–10 and 0–10% NaCl, indicating that most of them were haloalkaliphiles. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the bacterial isolates belonged to three major taxa: Gammaproteobacteria (genera: Marinobacter, Nitrincola, Stentrophomonas), Actinobactera (genera: Kocuria, Brevibacterium, Dietzia) and Firmicutes (genus Planomicrobium). Gammaproteobacteria were the most abundant, following Actinobacteria and Firmicutes. Most of the strains isolated in the present study had the ability to produce extracellular hydrolytic enzymes such as lipases, amylases, proteases and DNases, making them important biotechnologically.