PROTEINASES AS PROBABLY FACTORS OF REGULATION OF COMPETITIVE RELATIONS AMONG MICROORGANISMS
The studies used the strains Enterococcus mundtii and Bacillus lentus, producing two different bacteriocin-like substances (BLIS) – the first acts on Gr(+), the second on Gr(-) bacteria. It is shown that there is no antagonism between the strains when the bacteria are grown together. However, after mixing the BLIS fractions isolated from the two strains, the activity of the resulting solution was lost only in relation to Listeria monocytogenes, retained to Escherichia coli and to other Gr(-) bacteria. The reason for this could be a protease secreted by a strain of bacilli. It was found that the proteolytic enzyme was present only in the BLIS B. lentus fraction, the presence of which was determined by the hydrolysis of casein. The protease activity was suppressed at 80 °C and completely disappeared after the addition of a specific inhibitor of serine proteases, phenylmethylsulfonyl fluoride (PMSF). Therefore, in the thermally treated BLIS mixture due to inactivation of the enzyme, the bacteriocidal activity against L. monocytogenes was completely preserved. The obtained data indicate that the secreted protease of bacilli of the B. lentus strain can act as an exogenous regulator of the activity of bacteriocins and other low molecular weight peptides in microbiocenoses.