Authigenic mineralization and detrital clay binding by freshwater biofilms: The Brahmani river,India

This study sought to understand the origin and fate of one of the bitumen mounds found on the bottom of Lake Baikal. These mounds are located at a depth of 900 m beneath oil spots detected on the surface of Lake Baikal (53° 18′24^″, 108° 23′20^″). The two mounds were sampled with a manipulator from a “MIR” deep-water manned submersible. Mature mound No. 8 was subjected to chemical and microbiological studies. Mound No. 3 was subjected only to chemical studies; we failed to perform microbiological analyses of this mound for logistic reasons. Oil spots collected from the water surface, samples of mound No. 3 and No. 8, were subjected to GC/MS analysis. The water contained aliphatic hydrocarbons with chains between C₈ and C₂₃, with the most abundant chain length being C₁₈. Mound No. 3 with the most abundant chain length being C₁₈ actively released oil droplets into the water. It contained 770 mg/g of C₁₃-C₃₂ n-alkanes, with a maximum at C₂₃ (160 mg/g). Mound No. 8 was inactive and contained 148 mg/g of aliphatic C₂₂-C₃₄ n-alkanes, with a maximum at C₂₅. Mound No. 8 also consisted of 3% inorganic matter, 48% unresolved complex mixture (UCM) and less than 1% other compounds (polyaromatic hydrocarbons, isoprenoids, carotenoids, and hopanes). The core of this sample used as inoculate, yielded Rhodococci when cultivated on oil as the only source of carbon. Cultivation of the sample on agar-containing Raymond inorganic medium with crude West Siberian oil as the only source of carbon revealed colonies of these bacteria, which all appeared identical. PCR was performed with DNA isolated from 5 colonies, using primers for 16S rRNA genes. Comparison of the sequences of the 5 PCR products over a length of 714 bp revealed that they were almost identical. Phylogenetic analysis of these homologous sequences showed that they were similar to the corresponding sequences of the genus Rhodococcus. Substrate demands, the morphology of the colonies, and SEM and TEM data confirmed that the isolates obtained could indeed be Rhodococci. All of the isolates could grow in bulk cultures with inorganic medium supplemented with crude oil. Moreover, all of the isolates degraded aliphatic hydrocarbons with lengths between C₁₁ and C₂₉. C₂₃-C₂₉ hydrocarbons were degraded completely. The isolates could grow at 4–37°C. The most unexpected finding was that of the many microorganisms capable of consuming oil, only Rhodococci exhibited this ability in the inactive bitumen mound. The possible mechanisms of how crude oil is transformed into bitumen mounds and mature bitumen are discussed.     

Thermophilic Bacteria in Lake Baikal Bottom Sediments Associated with Hydrocarbon Discharge

Microbiology - The research was aimed at detection of thermophilic microorganisms in Lake Baikal low-temperature sediments associated with discharge of gas-saturated fluids. Members of the order...     

Ecophysiological Characteristics of the Mat-forming Bacterium Thioplocain Bottom Sediments of the Frolikha Bay, Northern Baikal

A colorless sulfur bacterium of the genus Thioploca, which forms bacterial mats, was studied in the region of underwater thermal vents (Frolikha Bay, northern Baikal). The organism occurs under microaerobic conditions in top sediment layers, and its biomass can amount to 65 mg of wet weight per 1 kg of silt. Individual filaments of the bacterium penetrate the anaerobic zone to the depth of 19 cm. Thioplocais distributed in a mosaic pattern over the bottom of the bay. Thioplocamats are typically found near vents that discharge low-temperature underground water. In the form of separate filaments, this bacterium is more widely distributed in the top sediment layer, particularly in sediments with a more active sulfate reduction. The bacteria from the deep-water and coastal areas of the bay have different morphology. Cells of Thioplocaare able to accumulate nitrate, and the coefficient of nitrate accumulation in wet bacterial mass in relation to the near-bottom water is 1.3 × 10⁴, suggesting a similarity of metabolism with seawater species. A more lightweight isotopic composition of nitrogen in cell mass as compared to that of representatives of zoobenthos also indicates an active metabolism of nitrogen, apparently, in the process of nitrogen respiration. Comparison of the composition of stable isotopes of carbon in the biomass of representatives of different trophic levels, including Thioploca, found at a depth of 105 m indicates its planktonic origin, whereas, in the deeper bay region, the biomass of Thioplocaincorporates more of the light carbon originating from biogenic methane.     

Microbial diversity in the samples from archeological complexes of the Pazyryk culture (IV–III centuries BC) in northwestern Mongolia

Prokaryotes were analyzed in the samples of ice and soils collected by the joint Russian-German-Mongolian expedition (2006) at the site of archeological excavations of two Pazyryk culture mounds in the upper Olon-Kurin-Gol River on the southern slope of the Saylyugem Mountains, Mongolian Altai. Phylogenetic analysis of the 16S rRNA gene fragments of the cultured bacteria revealed three major groups wide-spread in permafrost soils: Firmicutes, Actinobacteria, and Gammaproteobacteria. Analysis of the total DNA from the samples revealed nonculturable bacteria of the phyla Alphaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Actinobacteria, Chloroflexi, Gemmatoidetes, Firmicutes, and CFB (Cytophaga-Flavobacteria-Bacteroidetes) isolated from the samples of permafrost soils (Arctic, tundra, and from Tibet highlands), groundwater, and Arctic and Antarctic ice cores.     

Unit activity in the superior colliculus after removal of corticofugal control

Changes in spontaneous and evoked unit activity in the superior colliculus of the cat were studied after unilateral blocking of corticofugal connections. Functional characteristics of the cells were compared in the intact and disconnected colliculus. In neurons on the side of the operation the spontaneous firing rate was reduced and responses to photic stimulation were virtually completely abolished: only 7.1% of collicular cells on the side of the operation responded to adequate stimulation. Effective mechanisms of corticofugal control, modulating the relaying of the efferent volley in the tectal neurons, evidently function in the superior colliculus.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 10, No. 1, pp. 54–61, January–February, 1978.     

Microbial community associated with <Emphasis Type="Italic">Thioploca</Emphasis> sp. sheaths in the area of the posolsk bank methane seep,southern baikal

Bacterial mats formed by a colorless sulfur bacterium Thioploca sp. in the area of the Posolsk Bank cold methane seep (southern Baikal) were studied using electron microscopy and phylogenetic analysis. Morphologically the bacteria were identified as Thioploca ingrica. Confocal microscopy of DAPI-stained samples revealed numerous rod-shaped, filamentous, and spiral microorganisms in the sheaths, as well as inside and between the trichomes. Transmission electron microscopy revealed nonvacuolated bacteria and small cells without cell envelopes within the sheath. Bacteria with pronounced intracytoplasmic membranes characteristic of type I methanotrophs were observed at the outer side of the sheath. Based on analysis of the 16S rRNA gene sequences, the following phyla were identified in the sheath community: Bacteroidetes, Nitrospira, Chloroflexi, Planctomycetes, Verrucomicrobia, γ-, and δ-Proteobacteria, Euryarchaeota, Crenarchaeota, and Thaumarchaeota, as well as anammox bacteria. A hypothetical scheme of matter flows in the Lake Baikal bacterial mats was proposed based on the data on metabolism of the cultured homologues.     

Adaptation of molecular genetic methods to study microorganisms associated with fish

A modern molecular genetic method has been adapted to study microorganisms associated with fish. A procedure for total DNA isolation from various organs and tissues of fish has been developed. Besides fish freshly caught, frozen and salted specimens were used. A bacterial PCR product was shown to amplify with highly conservative primers at an annealing temperature of 70–72°C from fish gills, liver, intestine, and skin.     

Ecophysiological features of mat-forming bacteria Thioploca in bottom sediments of Frolikha Bay, northern Baikal]

A colorless sulfur bacterium of the genus Thioploca, which forms bacterial mats, was studied in the region of underwater thermal vents (Frolikha Bay, northern Baikal). The organism occurs under microaerobic conditions in top sediment layers, and its biomass can amount to 65 mg of wet weight per 1 kg of silt. Individual filaments of the bacterium penetrate the anaerobic zone to the depth of 19 cm. Thioploca is distributed in a mosaic pattern over the bottom of the bay. Thioploca mats are typically found near vents that discharge low-temperature underground water. In the form of separate filaments, this bacterium is more widely distributed in the top sediment layer, particularly in sediments with a more active sulfate reduction. The bacteria from the deep-water and coastal areas of the bay have different morphology. Cells of Thioploca are able to accumulate nitrate, and the coefficient of nitrate accumulation in wet bacterial mass in relation to the near-bottom water is 1.3 x 10(4), suggesting a similarity of metabolism with seawater species. A more lightweight isotopic composition of nitrogen in cell mass as compared to that of representatives of zoobenthos also indicates an active metabolism of nitrogen, apparently, in the process of nitrogen respiration. Comparison of the composition of stable isotopes of carbon in the biomass of representatives of different trophic levels, including Thioploca, found at a depth of 105 m indicates its planktonic origin, whereas, in the deeper bay region, the biomass of Thioploca incorporates more of the light carbon originating from biogenic methane.