Anaerobic oxidation of petroleum hydrocarbons in enrichment cultures from sediments of the Gorevoy Utes natural oil seep under methanogenic and sulfate-reducing conditions.

This article presents the first experimental data on the ability of microbial communities from sediments of the Gorevoy Utes natural oil seep to degrade petroleum hydrocarbons under anaerobic conditions. Like in marine ecosystems associated with oil discharge, available electron acceptors, in particular sulfate ions, affect the composition of the microbial community and the degree of hydrocarbon conversion. The cultivation of the surface sediments under sulfate-reducing conditions led to the formation of a more diverse bacterial community and greater loss of n-alkanes (28%) in comparison to methanogenic conditions (6%). Microbial communities of both surface and deep sediments are more oriented to degrade polycyclic aromatic hydrocarbons (PAHs), to which the degree of the PAH conversion testifies (up to 46%) irrespective of the present electron acceptors. Microorganisms with the uncultured closest homologues from thermal habitats, sediments of mud volcanoes, and environments contaminated with hydrocarbons mainly represented microbial communities of enrichment cultures. The members of the phyla Firmicutes, Chloroflexi, and Caldiserica (OP5), as well as the class Deltaproteobacteria and Methanomicrobia, were mostly found in enrichment cultures. The influence of gas-saturated fluids may be responsible for the presence in the bacterial 16S rRNA gene libraries of the sequences of "rare taxa": Planctomycetes, Ca. Atribacteria (OP9), Ca. Armatimonadetes (OP10), Ca. Latescibacteria (WS3), Ca. division (AC1), Ca. division (OP11), and Ca. Parcubacteria (OD1), which can be involved in hydrocarbon oxidation.

[Diversity of cultured aerobic microorganisms in the areas of natural oil seepage on Lake Baikal].

The diversity of cultured aerobic organisms collected from water samples and bottom sediment from two areas of natural oil seepage on Lake Baikal has been researched. Representatives of Alpha-, Beta-, and Gammaproteobacteria have been found in samples collected near the BolTshaya Zelenovskaya River mouth, while near Cape Gorevoi Utes Betaproteobacteria were absent. Most cultures are characterized by a sufficiently high homology level (96-100%) with nucleotide sequences from the international database.

[Study on the Lake Baikal microbial community in the areas of the natural oil seeps].

We studied the composition of a natural microbial community, the distribution of different groups of microorganisms (including those able to degrade oil hydrocarbons) within the areas of natural oil seeps in the Lake Baikal. It was revealed that, in the bottom sediments, the oil-degrading microorganisms dominating the community have included the bacteria of g. Bacillus, while in the water column, dominating microbes are presented by species of genera Rhodococcus Pseudomonas, and Micrococcus. Under the conditions of the model experiment, the potential activity of Baikal microbes towards utilization of n-alcanes has been assessed. Under such conditions it was shown that the concentration of n-alcanes decreases to 60% during 20 days of the experiment (the initial oil concentration was 0.5 mg/l, i.e., ten maximal permissible concentrations, MPC).

[Comparative characteristics of microbial communities in two regions of natural oil seepage in Lake Baikal].

Microbial communities and hydrocarbon contents have been studied in two regions of natural oil seepage in Lake Baikal: (1) opposite the Bol'shaya Zelenovskaya River mouth (studied previously) and (2) near Cape Gorevoi Utes (discovered in 2005). The abundance of both heterotrophic and hydrocarbon-oxidizing microorganisms is significantly higher in water samples from the first region, where the oil is biologically degraded. In the surface soil layer at stations located in the immediate vicinity of oil seepage site, the abundance of n-alkane-oxidizing microorganisms reaches 2000 cells/ml, and that of oil-oxidizing microorganisms reaches 2600 cells/ml. In water samples from near Cape Gorevoi Utes, the abundance of these groups of microorganisms does not exceed 190 and 500 cells/ml, respectively.

[The early diagnosis, evaluation of treatment results and modelling of certain aspects of the pathogenesis of retinal dystrophy]. / Ranniaia diagnostika, otsenka rezul'tatov lecheniia i modelirovanie nekotorykh storon patogeneza distrofii setchatki.

The paper analyses results after a study of the functional state of pigmented epithelium and the retina in patients with a dry form of senile macular dystrophy as well as of experimental simulation of retinal dystrophy with the help of melatonin and its treatment by taurine. Melatonin in 10(-3) M concentration leads to development of dystrophic changes in pigmented epithelium and interacting with it structures, this being testified by remarkable lowering of EOG parameters and electron microscopic findings. Taurine in 10(-3) M concentration blocks the action of exogenic melatonin as well as has a pronounced positive action on metabolism of dystrophic changes in the pigmented epithelium and photoreceptors. Examination of patients with different stages of a dry form of senile macular dystrophy revealed statistically significant reduction of KA cEOG at the initial stage of the disease in the presence of normal ERG parameters. In 18% of patients, supernormal values of KA were recorded, that are likely to reflect the presence of "predystrophic hyperactivity" of the pigmented epithelium cells. In progression of the process, the further reduction of electrophysiologic values was recorded. The data obtained speaks about the important role of pigmented epithelium pathology in the pathogenesis of senile macular dystrophy and about high information value of the cEOG method for detection of early stages of the disease. It is believed that disturbances in melatonin metabolism can be one of causes leading to development of retinal dystrophy.