Phylogenetic diversity in sulphate-reducing bacterial communities from oxidised and reduced bottom sediments of the Barents Sea.

In the bottom sediments from a number of the Barents Sea sites, including coastal areas of the Novaya Zemlya, Franz Josef Land, and Svalbard archipelagos, sulphate reduction rates were measured and the phylogenetic composition of sulphate-reducing bacterial (SRB) communities was analysed for the first time. Molecular genetic analysis of the sequences of the 16S rRNA and dsrB genes (the latter encodes the ß-subunit of dissimilatory (bi)sulphite reductase) revealed significant differences in the composition of bacterial communities in different sampling stations and sediment horizons of the Barents Sea depending on the physicochemical conditions. The major bacteria involved in reduction of sulphur compounds in Arctic marine bottom sediments belonged to Desulfobulbaceae, Desulfobacteraceae, Desulfovibrionaceae, Desulfuromonadaceae, and Desulfarculaceae families, as well as to uncultured clades SAR324 and Sva0485. Desulfobulbaceae and Desulfuromonadaceae predominated in the oxidised (Eh = 154-226 mV) upper layers of the sediments (up to 9% and 5.9% from all reads of the 16S rRNA gene sequences in the sample, correspondingly), while in deeper, more reduced layers (Eh = -210 to -105 mV) the share of Desulfobacteraceae in the SRB community was also significant (up to 5%). The highest relative abundance of members of Desulfarculaceae family (3.1%) was revealed in reduced layers of sandy-clayey sediments from the Barents Sea area affected by currents of transformed (mixed, with changed physicochemical characteristics) Atlantic waters.

Aerotolerant Thiosulfate-Reducing Bacterium Fusibacter sp. Strain WBS Isolated from Littoral Bottom Sediments of the White Sea-Biochemical and Genome Analysis.

The strain WBS, an anaerobic, psychro- and halotolerant bacterium belonging to the genus Fusibacter, was isolated from the littoral bottom sediments of the White Sea, Arctic, Russia. Fusibacter bizertensis WBS grew at temperatures between 8 and 32 °C (optimum growth at 18-20 °C), pH between 5.2 and 8.3 (optimum growth at pH 7.2), and at NaCl concentrations between 0 and 70 g L-1 (optimum growth at 32 g L-1). It reduced sulfate, thiosulfate, and elemental sulfur into sulfide, and, probably, the strain is able to disproportionate thiosulfate. The strain also utilized a wide range of substrates as it is a chemoorganotrophic bacterium. Analysis of the sequenced genome revealed genes for all enzymes involved in the Embden-Meyerhof glycolytic pathway as well as genes for the non-oxidative stage of the pentose phosphate pathway. The presence of genes encoding aldehyde dehydrogenases and alcohol dehydrogenases also suggests that, in addition to acetate, alcohols can also be the fermentation products. The strain possessed superoxide dismutase and peroxidase activities and the ability to consume O2, which is in full accordance with the presence of corresponding genes of antioxidant defense in the genome. The phylogenetic analysis suggested that the strain WBS is the closest relative of Fusibacter bizertensis LTF Kr01T (16S rRNA gene sequence similarity 98.78%). Based on biochemical and genomic characteristics, the strain WBS is proposed to represent a novel aero-, halo- and psychrotolerant strain from the genus Fusibacter, isolated for the first time among its members from cold oxygenated marine bottom sediments.

The positive effect of exogenous hemin on a resistance of strict anaerobic archaeon Methanobrevibacter arboriphilus to oxidative stresses.

Methanogenic archaeon Methanobrevibacter arboriphilus (strains AZ and DH1), which is a strict anaerobic microorganism not able to synthesize heme, possessed a very high catalase activity in the presence of 20-50 µM hemin in a growth medium. We investigated the effect of various oxidative stresses (hydrogen peroxide and oxygenation) on M. arboriphilus cells grown on the standard nutrient medium supplemented with 0.1 % yeast extract, and on the same medium supplemented with hemin. It was demonstrated that 30 µM hemin had a very significant positive effect on the resistance of M. arboriphilus strains to H(2)O(2) and O(2) stresses because of 30- to 40-fold increase of heme catalase activity. Thus, hydrogen peroxide (0.6-1.2 mM) or oxygen (3-5 %) had a strong negative impact on low-catalase cultures grown in the hemin-free standard medium, whereas the presence of 30 µM hemin in the medium results in a high yield of biomass even under conditions of four times stronger H(2)O(2) and two times stronger O(2) stresses. The intracellular catalase activity reached a high level in 30-60 min after hemin was added to the nutrient medium, but the activity already increased about 5-7-fold in 6 min after hemin addition. Our experimental data suggest that exogenous hemin provides an effective antioxidative defense in representatives of the genus Methanobrevibacter, specially playing an important role in the puromycin-insensitive formation of the active heme-containing catalase from presynthesized apoenzyme and heme.

An oxygen reduction chain in the hyperthermophilic anaerobe Thermotoga maritima highlights horizontal gene transfer between Thermococcales and Thermotogales.

The hyperthermophile Thermotoga maritima, although strictly anaerobic, is able to grow in the presence of low amounts of O(2). Here, we show that this bacterium consumes O(2) via a three-partner chain involving an NADH oxidoreductase (NRO), a rubredoxin (Rd) and a flavo-diiron protein (FprA) (locus tags: TM_0754, TM_0659 and TM_0755, respectively). In vitro experiments showed that the NADH-dependent O(2) consumption rate was 881.9 (± 106.7) mol O(2) consumed min(-1) per mol of FprA at 37°C and that water was the main end-product of the reaction. We propose that this O(2) reduction chain plays a central role in the O(2) tolerance of T. maritima. Phylogenetic analyses suggest that the genes coding for these three components were acquired by an ancestor of Thermotogales from an ancestor of Thermococcales via a single gene transfer. This event likely also involved two ROS scavenging enzymes (neelaredoxin and rubrerythrin) that are encoded by genes clustered with those coding for FprA, NRO and Rd in the ancestor of Thermococcales. Such genomic organization would have provided the ancestor of Thermotogales with a complete set of enzymes dedicated to O(2)-toxicity defence. Beside Thermotogales and Thermococcales, horizontal gene transfers have played a major role in disseminating these enzymes within the hyperthermophilic anaerobic prokaryotic communities, allowing them to cope with fluctuating oxidative conditions that exist in situ.

In Vitro Evaluation of Probiotic Potential of Selected Lactic Acid Bacteria Strains.

Research of human microbiome demonstrates that in order to develop next generation of probiotic agents, it is necessary to choose bacterial strains featured by special properties, such as the ability of the cells to attach to intestinal walls, resistance to bile and acids, bacteriocin synthesis, antioxidative and antipathogenic activity, and survivability in intestines. Thirty-three strains of lactic acid bacteria of Lactobacillus and Lactococcus genera from the Lomonosov Moscow State University Collection of Microorganisms (CM MSU) have been tested for important probiotic properties which assist these bacteria to settle effectively in intestines: cell adhesion, ability to form biofilms, agglutination with lectin (concanavalin A), and antimicrobial activity. The results of experiments clearly demonstrate that all these properties can be classified as strain characteristics and differ even within the same species. Besides the cultures of Lactobacillus with good agglutination ability with concanavalin A (Lact. caucasicus CM MSU 155, Lact. brevis CM MSU 521), we also discovered strains with high adhesion properties (Lact. acidophilus CM MSU 146-89% affinity for hexadecane; Lact. paracasei CM MSU 527-85%; Lact. plantarum CM MSU 508-78%; Lact. caucasicus CM MSU 155-70%; and Lact. delbrueckii CM MSU 571-57%), biofilm formation ability with a hydrophobic carrier (Lact. plantarum CM MSU 588-OD590 of crystal violet extracts = 1.336; Lact. brevis CM MSU 521-OD590 = 1.207; and Lact. brevis CM MSU 535-OD590 = 1.151), and with high antimicrobial activity specially to Staphylococcus aureus. Lact. brevis CM MSU 521 possesses the best property combination, which makes it potentially applicable as a very good lactic acid probiotic strain.

Response of Desulfovibrio vulgaris Hildenborough to hydrogen peroxide: enzymatic and transcriptional analyses.

We studied the effect of hydrogen peroxide (H(2)O(2)) stress on the anaerobic sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough. In a lactate/sulfate medium, growth was affected from 0.1 mM H(2)O(2) and totally inhibited at 0.7 mM. Surprisingly, transcript analyses revealed that the PerR regulon exhibited opposite regulation in the presence of 0.1 and 0.3 mM H(2)O(2). The variations in peroxidase- and superoxide dismutase-specific activities in the cell-free extracts of H(2)O(2)-stressed cultures were related to changes in the corresponding transcript abundance. Our data suggest that sod, sor, ngr and tpx genes, in addition to the PerR regulon, belong to the H(2)O(2) stimulon.

Antimicrobial activity of different proteins and their fragments from Bacillus thuringiensis parasporal crystals against clostridia and archaea.

Proteins of parasporal crystals (Cry proteins) from entomopathogenic bacterium Bacillus thuringiensis (subspecies kurstaki, galleriae, tenebrionis) as well as some fragments of these proteins, obtained by limited proteolysis, are capable of antimicrobial action against anaerobic bacteria and archaea-Clostridium butyricum, Clostridium acetobutylicum and Methanosarcina barkeri. The MICs are 45-150 microg/mL. Electron microscopy showed that lysis of M. barkeri cells in the presence of 49kDa fragment of Cry3Aa toxin is generally similar to the bacterial cell lysis, which has been previously detected in the presence of Cry11A, Cry1Ab and other Cry proteins. The Cry1D-like toxin from crystals of B. thuringiensis subsp. galleriae has been put forward as an example of the supposition that cell wall and some of its components like teichoic acid and N-acetylgalactosamine have possible influence on Cry toxins, enhancing their antimicrobial activity. The possible ecological role of the antimicrobial activity of Cry proteins is also discussed.

The catalase and superoxide dismutase genes are transcriptionally up-regulated upon oxidative stress in the strictly anaerobic archaeon Methanosarcina barkeri.

Methanosarcina barkeri is a strictly anaerobic methanogenic archaeon, which can survive oxidative stress. The oxidative stress agent paraquat (PQ) suppressed growth of M. barkeri at concentrations of 50-200 microM. Hydrogen peroxide (H2O2) inhibited growth at concentrations of 0.4-1.6 mM. Catalase activity in cell-free extracts of M. barkeri increased about threefold during H2O2 stress (1.3 mM H2O2, 2-4 h exposure) and nearly twofold during superoxide stress (160 microM PQ, 2 h exposure). PQ (160 microM, 2-4 h exposure) and H2O2 (1.3 mM, 2 h exposure) also influenced superoxide dismutase activity in cell-free extracts of M. barkeri. Dot-blot analysis was performed on total RNA isolated from H2O2- and PQ-exposed cultures, using labelled internal DNA fragments of the sod and kat genes. It was shown that H2O2 but not PQ strongly induced up-regulation of the kat gene. PQ and to a lesser degree H2O2 induced the expression of superoxide dismutase. The results indicate the regulation of the adaptive response of M. barkeri to different oxidative stresses.