INHIBITION OF BACILLUS-CEREUS SPORE OUTGROWTH BY COVALENT MODIFICATION OF A SULFHYDRYL-GROUP BY NITROSOTHIOL AND IODOACETATE

Nitrosothiols with the general structure RSN.dbd.O were studied as a model system of bacteriostatic action toward outgrowing bacterial [B. cereus] spores. With a Taft plot analysis, the influence of the structure of the R group on the inhibitory effectiveness of a series of nitrosothiols showed that effectiveness as an inhibitor of B. cereus T outgrowth correlated with the electron withdrawal of R, but that size, shape, charge, hydrophobicity and transportability had little influence. This was interpreted to mean that nitrosothiols do not traverse the membrane to act. The Taft plot together with competition data between nitrosothiol and iodoacetate indicated that the mode of nitrosothiol action is the covalent modification of a SH group, probably to form RSN(OH).sbd.SX, where .sbd.SX is derived from a sensitive spore SH group. Cooperativity effects indicated that outgrowth inhibition is accompanied by a conformational change occurring on SH group modification, which is communicated among at least 3-5 subunits. Uptake of label during spore germination indicated that most of the SH groups which can be modified are associated with the inhibitory event. These data suggest that this SH group may be sufficiently unique that inhibitors designed to interfere specifically with it could have value as bacteriostatic agents.