The Microbial Community of Poultry Farm Waste and Its Role in Hydrogen Sulfide Production

Microbiology - The microbiota of chicken litter remains largely unexplored, despite its leading role in the formation of volatile odorants and unpleasant odors. One of the main components of the...     

Metagenomic Analysis of the Microbial Community in the Underground Coal Fire Area (Kemerovo Region,Russia) Revealed Predominance of Thermophilic Members of the Phyla Deinococcus-Thermus,Aquificae, and Firmicutes

Microbiology - Underground burning of coal seams accompanied by release of gases leads to development of local thermal ecosystems. We investigated the microbial community of the ground heated to...     

Application of Microbial Mats for the Isolation of Spore-Forming Prokaryotes from Deep Biosphere

Microbiology - Deep biosphere is an prolific source of novel prokaryotes. A phylogenetically distant lineage of Firmicutes was reported in 2019 as a new genus Thermoanaerosсeptrum. Ecology of...     

European checkerspots (Melitaeini: Lepidoptera,Nymphalidae) are not aposematic – the point of view of great tits (Parus major)

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Formation of Covellite (CuS) Under Biological Sulfate-Reducing Conditions

Sulfate-reducing bacteria (SRB) play a major role in the precipitation of metal sulfides in the environment. In this work, biogenic copper sulfide formation was examined in cultures of SRB and compared to chemically initiated Cu sulfide precipitation as a reference system. Mixed cultures of SRB were incubated at 22, 45, and 60°C in nutrient solutions that contained copper sulfate. Abiotic reference samples were produced by reacting uninoculated liquid media with Na₂S solutions under otherwise identical conditions. Precipitates were collected anaerobically by centrifugation, frozen in liquid N₂, and freeze-dried, followed by analysis using X-ray diffraction (XRD), X-ray fluorescence, and scanning electron microscopy. Covellite (CuS) was the only mineral found in the precipitates. Covellite was less crystalline in the biogenic precipitates than in the abiotic samples based on XRD peak widths and peak to background ratios. Poor crystallinity may be the result of slower precipitation rates in bacterial cultures as compared to the abiotic reference systems. Furthermore, bacterial cells may inhibit the nucleation steps that lead to crystal formation. Incubation at elevated temperatures improved the crystallinity of the biotic specimens.     

Components of antioxidant systems in the cells of aerotolerant sulfate-reducing bacteria of the genus <Emphasis Type="Italic">Desulfovibrio</Emphasis> (strains A2 and TomC) isolated from metal mining waste

Two strains of sulfate-reducing bacteria of the genus Desulfovibrio (A2 and TomC) isolated from metal mining waste were able to grow on agar Postgate C nutrient medium under microaerobic conditions. Since their growth in liquid nutrient medium was just slightly affected by 1% O₂ (initial concentration in the gas phase) and 0.05–0.1 mM H₂O₂, these strains were relatively oxygen-tolerant. Only the presence of oxidants in high concentrations (5–10% О₂ or 0.3–1.0 mM H₂O₂) resulted in practically complete inhibition of their growth. Strain A2 was more resistant to oxidative stresses than strain TomC. Activities of the key enzymes of antioxidant defense—superoxide dismutase (SOD), catalase, and peroxidase—were revealed in the cell-free extracts of strain A2 grown under strict anaerobic conditions. While strain TomC was found to possess no peroxidase activity, its catalase activity was much higher than that of strain A2 (36 and 2 U/mg protein, respectively). SOD activity of both strains was almost the same (5 U/mg protein). Sublethal H₂O₂ doses (concentration of 0.05–0.15 mM and exposure for 45–240 min) resulted in a drastic increase of catalase activity, especially in strain A2. Sublethal О₂ doses (1–2% in the gas phase) had no significant effect on activities of the antioxidant enzymes of both strains. The cytochrome composition determined from the absolute absorption spectra of the whole cells of strains TomC and A2 revealed the presence of the c heme (438 and 831 pmol/mg protein) and the d heme (336 and 303 pmol/mg protein, respectively). The presence of the d heme indicated the presence of the bd heme–heme quinol oxidase, which together with the c heme may provide for the functioning of the electron transport segment of the antioxidant defensive system, which is responsible for aerotolerance of sulfate-reducing bacteria.     

Firmicutes is an Important Component of Microbial Communities in Water-Injected and Pristine Oil Reservoirs,Western Siberia,Russia

The dominant microbial components of fluids from wells in pristine and water-injected, high-temperature, Western Siberian oil fields, were analyzed by PCR-DGGE. Particular emphasis was placed on sulphate-reducing organisms, due to their ecological and industrial importance. Bacterial phylotypes obtained from the non-water-injected Stolbovoye oil field were more diverse than those from the Samotlor field, which is subject to secondary oil recovery by reinjection of recycled production water. The majority of phylotypes from both sites were related to Firmicutes. The low similarity to their closest relatives indicates unique bacterial communities in deep underground production waters and crude oil. Archaeal phylotypes detected only in the Samotlor samples were represented by Methanosarcinales and Methanobacteriales.     

Copper resistance in Desulfovibrio strain R2

A sulfate-reducing bacterium, designated as strain R2, was isolated from wastewater of a ball-bearing manufacturing facility in Tomsk, Western Siberia. This isolate was resistant up to 800 mg Cu/l in the growth medium. By comparison, Cu-resistance of reference cultures of sulfate-reducing bacteria ranged from 50 to 75 mg Cu/l. Growth experiments with strain R2 showed that Cu was an essential trace element and, on one hand, enhanced growth at concentrations up to 10 mg/l but, on the other hand, the growth rate decreased and lag-period extended at copper concentrations of >50 mg/l. Phenotypic characteristics and a 1078 bp nucleotide sequence of the 16S rDNA placed strain R2 within the genus Desulfovibrio. Desulfovibrio R2 carried at least one plasmid of approximately of 23.1 kbp. A 636 bp fragment ot the pcoR gene of the pco operon that encodes Cu resistance was amplified by PCR from plasmid DNA of strain R2. The pco genes are involved in Cu-resistance in some enteric and aerobic soil bacteria. Desulfovibrio R2 is a prospective strain for bioremediation purposes and for developing a homologous system for transformation of Cu-resistance in sulfate-reducing bacteria. This revised version was published online in June 2006 with corrections to the Cover Date.     

Flavonoid Production in Transformed Scutellaria baicalensis Roots and Ways of Its Regulation

A root culture of skullcap (Scutellaria baicalensisGeorgi) transformed with pRi T-DNA was initiated by the inoculation of sterile seedlings with Agrobacterium rhizogenes(wild-type strain A-4). The flavonoid concentration in cultured roots comprised 5% of the root dry weight and was maintained essentially constant during a subculture. For four weeks of culturing, the weight of the roots increased by 20–30 times; when the roots were cultured for a longer time and with periodic enrichment of the nutrient medium, their weight increased 50-fold. Skullcap roots were shown to synthesize flavones characteristic of intact roots (wogonin, baicalein, and baicalin). The addition of 0.01–1 mM L-phenylalanine (a precursor of flavonoids) to the nutrient medium affected neither root growth, nor their flavonoid concentration. Root elicitation with 100 M methyl jasmonate for 72 h increased the flavonoid content per flask and per root dry weight by 1.8 and 2.3 times, respectively.     

Growth of sulfate-reducing bacteria with solid-phase electron acceptors

Hannebachite (CaSO3 x 0.5H2O), gypsum (CaSO4 x 2H2O), anglesite (PbSO4), and barite (BaSO4) were tested as electron acceptors for sulfate-reducing bacteria with lactate as the electron donor. Hannebachite and gypsum are commonly associated with flue gas desulfurization products, and anglesite is a weathering product found in lead mines. Barite was included as the most insoluble sulfate. Growth of sulfate-reducing bacteria was monitored by protein and sulfide (dissolved H2S and HS-) measurements. Biogenic sulfide formation occurred with all four solid phases, and protein data confirmed that bacteria grew under these electron acceptor conditions. Sulfide formation from gypsum was almost comparable in rate and quantity to that produced from soluble sulfate salt (Na2SO4); hannebachite reduction to sulfide was not as fast. Anglesite as the electron acceptor was also reduced to sulfide in the solution phase and galena (PbS) was detected in solids retrieved from spent cultures. Barite as the electron acceptor supported the least amount of growth and H2S formation. The results demonstrate that low-solubility crystalline phases can be biologically reactive under reducing conditions. Furthermore, the results demonstrate that galena precipitation through sulfide production by sulfate-reducing bacteria serves as a lead enrichment mechanism, thereby also alleviating the potential toxicity of lead. In view of the role of acidophilic thiobacilli in the oxidation of sulfides, the present work accentuates the role of anaerobic and aerobic microbes in the biogeochemical cycling of solid-phase sulfates and sulfides.