[Effect of lipolytic and catalase activity on physico-mechanical properties of coating Polyken 980-25].

Lipolytic and catalase activity of Pseudomonas pseudoalcaligenes 109, Rhodococcus erythropolis 102, Bacillus subtilis 138 and their association with different growth models: biofilm and plankton ones. It is shown that under biofilm conditions the fermentative activity of bacteria under study was 1.5-1.7 times higher than under plankton conditions. Monocultures of bacteria displayed much lower activity than associative ones. Changes of physico-chemical properties of the specimens of protective coating Polyken 980-25 with participation of the above bacteria have been studied. The coating breaking strength decreases by 5.9-11.8% under the effect of monocultures, and by 17.3% under the effect of association. The adhesive strength as the basic index of coating biologic resistance decreased, respectively, in mono- and associated cultures by 28.6-73.2% in respect of the control. Damaging the sticking layer of isolation coating, bacteria damage the adhesion to metal which favors its corrosion.

[Monosaccharide and fatty acid composition of exopolymer complex of bacteria-destructors of the protective coating of gas pipeline].

Monosaccharide and fatty acid composition of the exopolymer complex (EPC) of heterotrophic bacteria Pseudomonas pseudoalkaligenes 109, Pseudomonas sp. T/2, Rhodococcus erythropolis 102--destructors of the protective coating Polyken 980-25 has been studied. It is shown that qualitative and quantitative composition of EPC components changes depending on the model of bacteria growth. Arabinose, mannose, galactose and glucose are dominating saccharides. Xylose has been revealed only under conditions of the biofilm form of growth of all the studied bacteria; ribose only in the biofilm of Pseudomonas sp. T/2. The fatty acid composition of EPC contains saturated and unsaturated acids with 12-19 carbon atoms. Hexadecanoic acid (C 16:0) acid which content in the biofilm and plankton conditions is from 24.9 to 32.4% prevailed in the spectrum of fatty acids of EPC bacteria. Unsaturated fatty acids: hexadecanoic (C 16:1) and octadecenoic (C 18:1) ones have been revealed only in the biofilm of bacteria-destructors of the coating.

[Monosaccharide composition of exopolymer complex of bacteria-destructors of protective coatings].

Monosaccharide composition of exopolymer complex (EPC) ofbacteria-destructors of protective coatings Pseudomonas sp. T/, Pseudomonas sp. 109, Arthrobacter sp. 102 has been studied. It is established that monosaccharide composition of exopolymer complex of bacteria is different and depends on the bacteria growth model. It is mainly represented by penthoses and hexoses. Glucose, galactose, arabinose, which are determined in EPC of biofilm and plankton of all studied bacteria, are dominating monosaccharides. Glucose content in the biofilm is from 22.6% to 39%; galactose--from 17% to 26.4%; arabinose--from 0.4 to 31.6%. Mannose is also synthesized by the studied bacteria, but in less quantity than other monosaccharides. Rhibose is found in EPC of Pseudomonas sp. st. 109, xylose--EPC biofilm of all studied bacteria.

[Lipolytic and catalase activity of bacteria-destructors of protective coatings].

Lipolytic and catalase activity of bacteria-destructors of protective coatings at different growth models: biofilm and plankton have been studied. It was shown that the synthesis of exoenzymes in the biofilm is different. Activity of extracellular lipase and catalase in the biofilm is 1.1-1.5 and 1.2-2.1 times higher, respectively, than in plankton. The experiment duration being increased to 14 days, the lipolytic activity considerably decreases. Activity of studied enzymes, produced by bacteria-destructors, can be used for estimating bioresistance of isolating coatings as the index of their biodegradation in technogenic media.

[Microbial biofilms on protective coatings of underground metal structures].

Biofilms are highly organized groupings which are formed by microorganisms of one or several species and consist of actively functioning cells, those at rest as well as of the forms which are not cultivated. The survey includes data concerning formation of biofilms and factors affecting the process of their development. The paper deals with the mechanisms of biofilms formation in bacteria and with the methods connected with obtaining and studying mutants of bacteria imperfect as to biofilms formation. The role of exopolymers in the structure and function of biofilms is discussed.

[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.

[Methods for estimation of microbe resistance of protective coatings]. / Metody otsenki mikrobnoi stoikosti zashchitnykh pokrytii.

Methods are proposed which permit estimating bioresistance of protective materials against denitrifying hydrocarbon-oxidizing and sulphate-reducing bacteria-destructors of coatings in laboratory conditions. The methods are based on the quantitative determination of bacteria growth in presence of coatings as the only source of hydrocarbon. Besides, attention is given to changes of certain indices of physico-mechanical properties of coatings: breaking strength and adhesion strength for coatings from polymeric bands, softening and expansion temperature for mastic materials.

[Formation of microbial populations on the surface of protective coatings]. / Formirovanie mikrobnykh soobshchestv na poverkhnosti zashchitnykh pokrytii.

Formation of microbial cenosis on the surface of polyethylene-, polyurethane- and oil-bitumen-based protective coatings was studied in dynamics during 1, 3, 7, 14 and 21 days. It has been shown that the biofilm was formed on the protective materials during 14 days and consisted of ammonifying, denitrifying, hydrocarbon-oxidizing and sulphate-reducing bacteria referred to Pseudomonas, Arthrobacter, Bacillus and Kesulfovibrio genera. The bacteria which form the biofilm on coatings possess high denitrifying and sulphate-reducing activities. Corrosion inhibitors-biocydes, introduced in composition of oil-bitumen coatings suppressed growth and metabolic activity of corrosion-active bacteria.