Cytochemical Mechanisms of Penicillin Action

Abstract

In a previous paper we described the gross appearance of penicillin assay plates after chemical treatments which reveal sharp boundaries around the zones of inhibition (Dufrenoy and Pratt, 1947). Most of the tests that were described are effective following exposure of the test organisms to penicillin for periods as short as 2 to 3 hours, i.e., before zones of inhibition are discernible on untreated plates. Several of the tests may find application as rapid cylinder plate assay methods (Pratt and Dufrenoy, 1947). The sharp delineation of the inhibition zones was interpreted as an expression of a threshold effect; positive reactions for-SH groups and for OH=C-C==OH groups were obtained outside the zones of inhibition, but not inside. The evidence suggested an increase.of rH within the zones and that this increase was correlated with inhibition of dehydrogenase systems. Since there is strong evidence in the literature that dehy-I The execution of the work reported in this paper was made possible by a generous research grant from the