卷 87, 编号 4 (2018)

Analysis of the literature and GenBank data showed that the genus Ogataea is heterogeneous and includes at least five non-described genera. Comprehensive phylogenetic analysis of the present genus Ogataea may be conducted only based on multigene analysis of all the known species. Possibilities of molecular species identification in biogeographical and ecological studies of yeasts are discussed.

Biodegradation of crude oil components by strain AG_S10, an acidophilic member of the genus Mycobacterium, was studied under extremely acidic conditions (pH 2.5). The degree of degradation of the same hydrocarbons in different kinds of oil was found to be different. The direction of biodegradation was, however, the same: the share of n-alkanes in oxidized oil decreased, while the share of branched alkanes increased. At the same time, the degree of redistribution of methane hydrocarbons in degraded oil varied significantly for different oils, although no strict dependence on the type of oil was found. After 28 days of incubation at 30°C and pH 2.5, the degradation of n- and iso-alkanes was 99 and 44%, respectively for the light, low-viscosity oil of the Nizhnevartovsk deposit, 58 and 32%, respectively for the medium-density oil of the Moscow oil-procesing plant, and 80 and 16% and 99 and 69%, respectively for the heavy, viscous oils of the Cheremukhovskoe and Usinkoye oil fields. Moreover, after extended cultivation time strain AG_S10 completely utilized alkanes, as well as a significant part of the naphthene component of the aliphatic fraction. The studied strain was characterized by ability to oxidize a broad spectrum of methane hydrocarbons, including high-molecular C₁₇–C₃₀n-alkanes, in oils of different properties and composition. Apart from its scientific interest, farther investigation of biodegradation of high-paraffin oils and viscous oils with elevated paraffin content by strain AG_S10 may be useful in view of the technical issues associated with paraffin accumulation in the course of recovery and transportation of these oils.

Chitinase is one of the most important enzymes due to its diversity and a variety of potential uses. This study is an attempt to enhance chitinase production for antifungal biocontrol by subjecting Bacillus thuringiensis NM101-19 strain grown on shrimp shell wastes to various doses of gamma irradiation. Six mutants (BM-4, BM-6, BM-8, BM-12, BM-15, and BM-17) obtained at gamma ray doses of 40, 60, 80, 100, 120 and 140 Gy, respectively produced higher levels of chitinolytic activities in comparision to the wild-type strain. The BM-15 mutant strain showed the highest chitinase production (65.41 U/mL) which was 2.60 times more than the wild type (25.11 U/mL). Biocontrol efficacy of the mutants was statistically superior to the wild-type strain against all tested phytopathogens. Random amplified polymorphic DNA (RAPD) and inter simple sequence repeat (ISSR) PCR techniques, with five primers for each, were used in order to detect the variation in DNA profile between the mutant and wild-type strains in response to gamma-radiation treatments. RAPD and ISSR analysis indicated the appearance and disappearance of DNA polymorphic bands at different gamma ray doses. The results confirmed that the mutagenesis technique is a potent strategy to enhance the chitinase activity for industrial and agricultural purposes.

A thermophilic, anaerobic, chemolithoautotrophic bacterium (strain SU872^T) was isolated from a shallow-sea hydrothermal vent at Kunashir Island. The cells were motile, gram-negative, oval or rodshaped 0.5‒0.6 μm thick and 1.5‒2.0 μm long, occurring singly or in pairs. Strain SU872^T grew at 50 to 79°C (optimum at 74°C), pH from 5.0 to 8.0 (optimum at 6.7‒7.0), and NaCl concentration of 1.5–4.5%. Strain SU872^T was able to grow by disproportionation of elemental sulfur, thiosulfate, or sulfite, with CO₂/HCO₃⁻ as the sole carbon source. Growth was enhanced in the presence of ferrihydrite (poorly crystalline Fe(III) oxide) as as a sulfide-scavenging agent. Sulfate was not used as an electron acceptor. Growth also occurred with elemental sulfur, thiosulfate, or sulfite (but not sulfide) as electron donors and nitrate as an electron acceptor, with production of sulfate and ammonium. Analysis of the 16S rRNA gene sequence revealed 97.8% similarity between strain SU872^T and the type strain Thermosulfurimonas dismutans S95^T (phylum Thermodesulfobacteria). According to the results of DNA–DNA hybridization, the similarity of genomic DNA of the strains SU872^T and T. dismutans S95^T was 48%. Based on its phenotypic characteristics and the results of phylogenetic analysis, it is proposed to assign the isolate to a new species of the genus Thermosulfurimonas,—Thermosulfurimonas marina sp. nov., with the type strain SU872^T (=DSM 104922^T, =VKM B-3177^T, =UNIQEM SU872^T).

Investigations on the microbial life in several coastal solar salterns have revealed the presence of novel organisms and synthesis of unusual molecules active in extreme conditions which might be useful in different biotechnological industries. Biodiversity of heterotrophic aerobic bacteria isolated from two salterns, Pomorie salterns and Burgas salterns located at Burgas Bay, Black Sea coast, Bulgaria, as well as ability of the isolates to synthesize biotechnologically valuable compounds were investigated. The results revealed high taxonomic and metabolic bacterial diversity—we isolated 20 morphologically different moderately halophilic and two halotolerant strains affiliated with 11 species from eight genera referred to the phyla Proteobacteria, Firmicutes, and Actinobacteria. Gram-negative bacteria belonged to the genera Halomonas, Chromohalobacter, Salinivibrio, Cobetia, and Nesiotobacter, and gram-positive strains were representatives of the genera Virgibacillus, Salinicoccus, and Brevibacterium. All isolates were found to be alkalitolerant, and 41% of them were psychrotolerant. The strains degraded nine of the tested 18 substrates; polygalacturonase, catalase, phytase, and lipase producers were predominant. This is the first reported detection of xanthan lyase, gellan lyase, arabinase, and phytase activities in halophilic bacteria. Nine of the strains belonging to five different genera were found to produce exopolysaccharides (EPS). The highest level of EPS was observed in Chromohalobacter canadensis strain 28. More than a half of the strains displayed antimicrobial activity against one to five test bacteria and yeasts. The present study is the first report on halophilic bacteria isolated from salterns at the Black Sea coast indicating that the investigated area is an untapped resource of halophilic bacteria with biotechnological potential.

Three strains of haloalkaliphilic bacteria were isolated from microbial mats of soda-saline lakes of the Badain Jaran Desert, Inner Mongolia (China). Based on the data on ribosomal phylogeny, they were identified as members of the genus Halomonas. These bacteria were moderate alkaliphiles and extreme halophiles. The peptidases secreted by these bacteria were shown to have narrow substrate specificity. They hydrolyzed proteins and para-nitroanilide substrates and showed maximal activity in the hydrolysis of L-leucyl-p-nitroanilides (LpNA). The maximum activity of the peptidases occurred at alkaline pH values (8–10) and elevated salinity (50–100 g/L); the enzymes were thermostable (up to 50°С). The results of inhibitor analysis and substrate specificity examination of extracellular enzymes indicated them to belong to the class of aminopeptidase-like metallopeptidases.

The goal of the work was to reveal the differences in the structure of microbial communities of Transbaikalia alkaline lakes stemming from the differences in their salinity and hydrochemical parameters. The lakes studied were Verkhnee Beloe (Buryat Republic, Russia), as well as Khilganta, Gorbunka, and Borzinskoe (Transbaikal krai, Russia) with salinity from 12.3 to 430 g/L, which differed in the mineral composition of the sediments and hydrochemical parameters. Lake sediments were found to contain 47 prokaryotic phyla (42 bacterial and 5 archaeal ones). The phyla Proteobacteria, Euryarchaeota, Bacteroides, Chloroflexi, Actinobacteria, and Firmicutes were predominant, comprising over 95% of the classified sequences. Comparative abundance of archaea increased with salinity from below 1% in Lake Verkhnee Beloe to 35% in Lake Borzinskoe. The most numerous bacterial OTUs belonged to gammaproteobacteria of the genus Halomonas (up to 15% of the number of classified sequences). The most numerous archaeal OTUs were identified at the genus level as members of the genera Halorubrum and Halohasta belonging to the family Halorubraceae, which comprises extremely halophilic Euryarchaeota.

Clone libraries and morphological analysis were used to investigate cyanobacterial diversity in the cyanobacterial mat and dry crust at the bottom of the shallow, saline, alkaline Lake Khilganta (Southern Siberia, Russia). Filamentous cyanobacteria belonging to Phormidium genus and Coleofasciculus chthonoplastes were found to predominate during the dry period (2006) and the wet periods (1995 and 2012), respectively. Community composition during the dry and wet periods differed significantly. While 11 operational taxonomic units of cyanobacteria were revealed, only 3 occurred during both dry and wet periods. Occurrence of cosmopolitan C. chthonoplastes, which is common in neutral saline environments, is not typical of a continental alkaline lake and may be explained by the similarity of the dominant ions composition in lake water and in seawater.

Central Asia is one of the world largest regions, which has been relatively poorly studied from the microbiological point of view. The lakes of this region have a broad range of ecological conditions, from lowmineral to hypersaline ones. Long-term observations revealed that microbial communities of these lakes reflect the climatic and ecological changes in this region. Genomic research showed that some microbial species were found only in Central Asian lakes, but not in other regions of the world. The combination of these factors makes Central Asian lakes a promising subject for microbiological investigation.