OBJECTIVE Study of bactericidal effect of phenol on Yersinia pseudotuberculosis produced in various nutrient media. METHODS Bacteria were produced in nutrient broth (NB) and NB with glucose (NB+Glu) or galactose (NB+Gal) at 8 degrees C. Effect of phenol on bacteria was evaluated by changes in optical density of suspension and quantity of viable cells, and by staining of cells with ethidium bromide. Lipids were analyzed by thin-layer and gas-liquid chromatography, gas-liquid- chromatography--mass-spectrometry, differential scanning calorimetry; lipopolysaccharides (LPS)--by electrophoresis in polyacrylamide gel in the presence of sodium dodecylsulfate (SDS-PAGE). RESULTS Survival rate of bacteria is dependent on phenol concentration, biocide treatment time and parameters of cell cultivation. Addition of glucose or galactose into the nutrient medium increases the resistance of Yersinia against phenol. Bacterial cultures are heterogeneous in the resistance against phenol independently of the production parameters. Phenol causes damage in outer bacterial membrane, as evidenced by accumulation of lysophosphatidylethanolamine in the cell, the main product of enzyme activity of membrane-bound phospholipase A, and release into the cultural medium of part of LPS. Treatment by phenol in bactericidal concentration is accompanied by changes in phospholipidic and fatty acid composition of bacterial cell envelope. CONCLUSIONS New data are obtained on environmental factors that contribute to the increase of resistance of bacteria against phenolic biocides.