[Biodiversity of sulfate-reducing bacteria growing on objects of heating systems].

It was shown that sulfate-reducing bacteria developed on the sections of Kyiv municipal heating systems, which are exploited in conditions of different temperatures. The bacteria were different as to their morphological and physiological properties. The bacteria of Desulfovibrio genus were revealed on the sections, which were exploited at a temperature of 35-40 degrees C and bacteria of Desulfomicrobium and Desulfotomaculum genera were revealed on the sections with a higher temperature such as 60 degrees C. Based on of the 16S rRNA gene analysis data, it was demonstrated that sequences of TC2, TC3 and TC4 clones related to Desulfovibrio sp. DSM 12803 (100% sequence similarity), Desulfotomaculum sp. ECP-C-5 (92% sequence similarity) and Desulfomicrobium baculatum strain DSM 2555 (99% sequence similarity), respectively. The identified bacteria are potentially dangerous for heating systems and can be the agents of microbial corrosion.

[Lectin-binding analysis of the biofilm exopolymeric matrix carbohydrate composition of corrosion-aggressive bacteria].

The carbohydrate components of biofilms of corrosion-aggressive bacteria were studied by transmisstion electron microscopy using lectins labeled with colloidal gold. N-acetyl-D-glucosamine, N-acetyl-D-galactosamine, and neutral carbohydrates D-glucose and D-mannose were found within the exopolymeric matrix. Lectins with equal carbohydrate specificity demonstrated different degrees of interaction with the carbohydrate components of bacterial biofilms. To identify N-acetyl-D-galactosamine in biofilms of Desulfovibrio sp. 10 and Bacillus subtilis 36, the LBA lectin appeared to be most specific; in the case of N-acetyl-D-glucosamine in biofilms of B. subtilis 36 and Pseudomonas aeruginosa 27, the WGA lectin. During visualization of neutral carbohydrates in the studied cultures, the PSA lectin was most specific. We have shown that lectins labeled with colloidal gold could be used as an express method for the identification and localization of carbohydrates in glycopolymers of the biofilm exopolymeric matrix.

[Possibility of the plasmid transfer within bacteria - compounds of the sulfidogenic microbial community].

Extrachromosomal elements have been found within the isolates of ammonifying and iron-reducing bacteria obtained from the natural sulfidogenic community. These elements were small with size approximately 5-9 kb. Transconjugant strains Pseudomonas aeruginosa 27, P aeruginosa 28, P mendocina 29, Aeromonas hydrophila/caviae 30, harboured plasmids RP4 and R68.45 were obtained. The conjugation rate and retention of the plasmid within transconjugants were studied. P mendocina 29 cells with conjugation rate - 3.0*10(-6) CFU/ recipient cell, and P. aeruginosa 27 with rate 2.4*l0(-7) CFU/recipient cell were the most susceptible to R68.45 plasmid. The most stable retention is shown for transconjugated strains such as P aeruginosa 27 (R68.45), P. aeruginosa 27(RP4), P. mendocina 29(R68.45), A. hydrophila/caviae 30(RP4), A. hydrophila/caviae 30(R68.45). Thus, it was experimentally shown that corrosive-relevant bacteria form sulfidogenic microbial community which is able to accept extrachromosomal genetic elements from other bacteria when they act as recipients in conjugational process.

[Role of polymer complexes in the formation of biofilms by corrosive bacteria on steel surfaces].

The composition of exopolymer complexes (EPCs), synthesized by the monocultures Desulfovibrio sp. 10, Bacillus subtilis 36, and Pseudomonas aeruginosa 27 and by microbial associations involved in the corrosion of metal surfaces has been studied. An analysis of the monosaccharide composition of carbohydrate components, as well as the fatty acid composition of the lipid part of EPCs, was carried out by gas-liquid chromatography (GLC). It was found that bacteria in biofilms synthesized polymers; this process was dominated by glucose, while the growth of bacteria in a suspension was marked by a high rhamnose content. Hexouronic acids and hexosamine have been revealed as a part of B. subtilis 36 and P. aeruginosa 27 EPCs. Qualitative differences were revealed in the fatty acid composition ofexopolymers in biofilms and in a bacterial suspension. It was shown that the transition to a biofilm form of growth led to an increase in the unsaturation degree of fatty acids in the exopolymers of associative cultures. The results can be used to develop methods to control microbial corrosion of metal surfaces.

[Role of exopolymeric substances of corrosion-aggressive bacteria in the biofilm formation on the steel surface].

It had been done the comparative study of the exopolymeric substances (EPS) synthesized by the sulfidogenic microbial community and monocultures of Desulfovibrio sp. 10, Bacillus subtilis 36 and Pseudomonas aeruginosa 27 under various growth models as biofilm and plankton was performed. It was established that biofilm-produced exopolymers contained increased amount of glucose and fucose, while planktonic ones had more amount of mannose and rhamnose. The amount of rhamnose was 24% of the total amount of carbohydrates in the planktonic-produced exopolymers synthesized by Pseudomonas aeruginosa 27 and Bacillus subtilis 36. Glucuronic acid, galactosamine and glucosamine along with neutral carbohydrates were found in the composition of EPS synthesized by associative cultures, while only galactosamine was found in EPS synthesized by Desulfovibrio sp. 10. The amount of hexuronic acids and hexozamines was, respectively, 4.6 and 1.6 times higher in the biofilm formed by Pseudomonas aeruginosa 27 on the steel surface, than in the planktonic exopolymers. It is discussed the role in the biofilm formation of dominative members of the corrosion-aggressive microbial community.

[Taxonomic position of certain representatives of sulphate-reducing corrosive microbial community].

Sulfate-reducing bacteria and their heterotrophic satellites have been isolated from the biofilm formed on steel by sulfidogenic corrosive microbial community. Bacteria were characterized according to phenotypical features and investigated by the methods of molecular-genetic analysis. In accordance with the phenotypical features the studied strain of sulfate-reducing bacteria were related to Desulfovibrio genus, Gram-positive strains of heterotrophic satellites were related to Bacillus genus, B. firmus and B. subtilis species. Gram-negative strains, as to their physiological-biochemical characteristics were related to Pseudomonas genus, P. aeruginosa species, Stenotrophomonas genus, S. maltophilia species, and Aeromonas genus, A. hydrophila/caviae species. Taxonomic position of certain representatives of the community is confirmed by the molecular-genetic methods. A comparative analysis of the sequencing results has evidenced for the identity of sequences of 16S rRNA of the studied bacteria with analogous sequence of strains from the GenBank database. Nucleotide sequence of strain 27 has a 99% homology with the sequence of Pseudomonas aeruginosa, strain 36 deposited at GenBank to nucleotide sequence of Bacillus subtilis. As to sulfate-reducing bacteria, only their belonging to Desulfovibrio genus has been confirmed. Thus the results of sequence-analysis of 16S rRNA genes are in agreement with the data obtained from studying the phenotypical features.

[Development of mono- and associative cultures of sulphate-reducing bacteria and formation of exopolymeric complex].

Differences were found in development of the monoculture of sulphate-reducing bacteria Desulfovibrio sp. Kyiv-10 and artificial associations of cultures of sulphate reducing bacteria with heterotrophic satellites under development in a form of biofilm or plankton. Correlation between exopolymers synthesis in the biofilm and steel corrosion velocity has been found. Glucose, galactose, mannose, xylose, rhibose and nonidentified carbohydrates were found in the composition of exopolymers synthesized by monoculture Desulfovibrio sp. Kyiv-10 under its development in a form of biofilm. The biofilm and plankton cells of associative cultures synthesized exopolysaccharide which included rhamnose, arabinose and fucose. Glucose content in biofilm EPM was considerably higher (41.0055.9%) than in EPM of plankton cells (24.7-32.8).

[Dynamics of successive changes in sulphidogenic microbial association under the conditions of formation of the biofilm on steel surface].

Dynamics of successive changes in the artificial associative culture of sulphate-reducing bacteria was investigated under biofilm formation on steel 3 specimens. It was shown that the ammonificating, denitrificating and iron-reducing bacteria were associative satellites of sulphate-reducing bacteria in the biofilm. Heterotrophic satellites ofsulphate-reductors with domination ofammonificating bacteria developed in the first hours of exposition in the microbial association. The appearance of sulphate-reducing bacteria in the biofilm was fixed on the 24th hour of exposition, their domination was noticed after 72 and 240 hours. It was shown that the successive changes with a consequent change of domination of different bacterial physiologic groups took place in the microbial association under the biofilm formation on the steel surface, that favoured mutually beneficial functioning of corrosion-dangerous bacteria.

[Effect of corrosion inhibitor on the producing of exopolymer complex by sulphate-reducing bacteria].

It is established that the specific productivity of exopolymer complex (EPM) synthesized by the cells of sulphate-reducing bacteria in a biofilm was 1.5 times higher than in plankton. A sharp increase of the specific productivity of EPM in the biofilm is observed when corrosion inhibitor is introduced in the environment. The inhibitor concentration being 1.0 g/l, the biofilm cells produced almost 18 times more of EPM than the bacteria cells in plankton. It is shown that the film exopolymers include glucose, galactose, mannose, xylose, ribose and three nondetermined sugars, while plankton cells also include rhamnose. Rhamnose appeared in the biofilm EPM composition and rhamnose, arabinose and fucose appeared in EPM of plankton cells as affected by the inhibitor. A necessity of investigating the biofilm formation for developing the methods of anticorrosive protection is discussed.

[Adhesion of sulphate-reducing bacteria to steel under cathode polarization].

Adhesion of different (as to their corrosion aggression) strains of sulphate-reducing bacteria to steel has been studied under cathode polarization at various potentials: -800, -900, -1000, -1200 mV. It has been established that cathode polarization differently affects the adhesion of strain of sulphate-reducing bacteria with various aggression to steel. Correlation between the bacterial strains aggression and the number of cells adhered to metal have been noted. The cells of aggressive strains of D. indonensis Indonesia and Desulfovibrio sp. Kiev-10 adhered to metal most actively at cathode depolarization (8.0 x 10(7) and 3.5 x 10(7) cell/cm2, respectively). Nonaggressive strains of bacteria D. desulfuricans Kiev-45 and Desulfobulbus sp. Portsmouth adhered to metal in a less quantity. The data obtained prove that the use of cathode protection without allowance for the microbe factor can lead to intensification of the corrosion process.

[Effect of sulfate-reducing bacteria on steel corrosion in the presence of inhibitors]. / Vliianie sul'fatredutsiruiushchikh bakterii na korroziiu stali v prisutstvii ingibitorov.

Steel 08KP corrosion was studied as affected by inhibitors in presence of sulphate-reducing bacteria (SRB). Organic compounds, containing functional groups with nitrogen, oxygen and sulphur atoms, were investigated as corrosion inhibitors. It is shown that the studied inhibitors may be divided into three groups as to the mechanism of protective action. It has been established that cation-active nitrogen-containing surfactants ([symbol: see text] X, [symbol: see text]-1, [symbol: see text]-1M, catapin M, [symbol: see text]-2M) are the most efficient steel corrosion inhibitors. Such inhibitors, when adsorbed on metal surface, can affect the process of hydrogen precipitation on its surface, and thus inhibit catalytic function of SRB as the depolarizer of cathode process.

[Assessment of biological corrosion of ferroconcrete of ground-based industrial structures]. / Otsenka biokorrozionnogo sostoianiia zhelezobetona nazemnykh promyshlennykh konstruktsii.

One of the objects of a nuclear plant built in 1983 and put in 15-years long dead storage with the purpose to estimate the degree of contamination by rust-hazardous microorganisms of ferroconcrete structures and to predict their biocorrosion state after putting in operation was a subject of microbiological investigation. The everywhere distribution of sulphur cycle bacteria (thionic and sulphate-reducing bacteria) on the surface and in the bulk of concrete structures, their confineness to corrosion products of concrete and bars of the investigated building have been shown. It has been demonstrated that sulphate-reducing bacteria were the most distributed group in all the sampling points. An indirect estimation of participation degree of the microbial communities in the processes of ferroconcrete biological damages has been carried out as based on the accumulation intensity of aggressive gaseous metabolites--carbon dioxide and hydrogen. Probability of deterioration of biocorrosion situation under the full-scale operation of the object has been substantiated.

[Microflora of damaged ferroconcrete structures under the conditions of inhibitory protection]. / Mikroflora povrezhdennykh zhelezobetonnykh konstruktsii v usloviiakh ingibitornoi zashchity.

Thionic, sulphate-reducing, denitrifying and ammonifying bacteria widely distributed in the sewer system on various structure elements have been isolated from damaged ferroconcrete samples. Effect of protective materials on microbe-induced corrosion of metal famework of concrete samples has been studied. Selective effect of corrosion inhibitors and coatings on the growth of corrosion-active bacteria of sulphur and nitrogen cycle has been revealed. It is shown that acid medium formed by thionic bacteria is more aggressive than ammonium-hydrosulphide one formed by denitrifying and sulphate-reducing bacteria. It has been established that the corrosion inhibitor--pyrquin, organosilicon coating CO-FMI and epoxyorganosilicon coating 4sk are most effective materials as to the action of thionic bacteria--dangerous agents of ferroconcrete aerobic corrosion.