[Biofilm on a metal surface as a factor of microbial corrosion].

Main attention was given in the present review to the research methods, phases of biofilm's forming, exopolymer compounds of bacteria as main biofilm forming factor. A microbial corrosion as a result of interaction between the biofilm and metal surface was considered. The interaction was displayed in biomineralization. The future trends of biofilms study were bound with research of their architecture. That architecture was determined by the structure and function of biofilms compounds: biopolymers and biominerals.

[Effect of nickel ions on physiological and corrosion activity of bacteria of sulfur cycle].

The paper deals with the effect of nickel ions concentration in nutrient medium on sulfate-reducing bacteria Desulfovibrio desulfuricans 10-V (SRB) and their artificial corrosion-active associations which included thionic bacteria and their satellite Stenotrophomonas maltophilia. It is shown that the concentration of nickel in the nutrient medium being increased, the duration of lag-phase of SRB growth became 2-2.5 times less, and that of artificial associations--3-3.5 times less. The specific growth rate did not change in all the experiment variants. At the same time the hydrogenase and corrosion activity of the studied cultures increases almost twice with nickel content increase in the cultural medium to 0.5 mg/ml. Further increase of nickel concentration did not cause the change of the above parameters.

[Effect of the biofilm biopolymers on the microbial corrosion rate of the low-carbon steel].

The relationship between exopolymer's specific production, relative carbohydrate and protein content in the biofilm exopolymers of the pure and mixed Thiobacillus thioparus and Stenotrophomonas maltophilia cultures and their corrosion activity was studied. Change of growth model of investigated cultures from plankton to biofilm led to an increase of specific exopolymer's production. In the biofilm formed by T. thioparus and S. maltophilia biofilm on the low-carbon steel surface one could observe an increase of relative protein content in the exopolymer complex in comparison with those in the pure culture. The development of such biofilms stimulatied the 7-fold corrosion activity.

[Monosaccharide composition of exopolymer complex in Thiobacillus thioparus and Stenotrophomonas maltophilia].

The bacteria of Thiobacillus thioparus and Stenotrophomonas maltophilia are capable to form a thick biofilm complicated as to its structure on the surface of low-carbon steel. This biofilm formation on any surface occurs under the adhesion of the cells of the plankton growth model with the help of synthesis of muciferous exopolymers with adhesive properties. Hence the monosaccharide composition of the exopolymer complex in the form of polyol acetates was studied by chromate-mass-spectrum method. A significant difference in the composition of exopolymer monosaccharides with the presence of steel model in the medium and without it was established; a change in the monosaccharide composition of mono- and binary culture in the conditions of plankton and biofilm growth was also observed.