Modifying action of C7-alkyloxybenzol (methylresorcin) on the antilysozyme activity (ALA) of opportunistic microorganisms (Bacillus cereus, Klebsiella pneumoniae, and Escherichia coli) was studied. C7-alkyloxybenzol (C7-AOB, methylrezorcin), which was used as chemical analogue of microbial autoregulators, was added to growth medium containing microorganisms, which were cultivated until entered stationary phase. Isolation of clones was performed by seeding of 24-hours broth culture on solid growth medium, and then ALA was measured using photometric method. Modifying action of C7-AOB on ALA characteristic-based population structure of B.cereus, K. pneumoniae, and E. coli was revealed. Maximal effect was detected when the concentration of C7-AOB was in range 1-10 mcg/ml. Decrease of mean ALA level caused by C7-AOB was linked to decrease of proportion of clones with high and intermediate ALA level, increase of proportion of clones with low level of lysozyme inhibitor, and emergence of clones lacking ALA in the population.