Abstract
Diethylpyrocarbonate (DEPC) exhibited a bacteriostatic effect at concentrations between 0.5 mM and 8 mM and a bactericidal effect at concentrations above 10 mM on Lactobacillus casei S-1. At the bacteriostatic concentrations the bacteria began to grow after the added DEPC had disappeared from the medium by self-decomposition, whereas at the bactericidal concentrations such growth was not observed even after long-term incubation.
DEPC inactivated free phage J1 within several min; 10, 20 and 30mM of DEPC inactivated the phage by 90, 99.9 and 100%, respectively. The inactivation by DEPC was enhanced slightly by high temperature and markedly by low pH. Metal ions and chelating agents rendered negligible effects on the inactivation percentage.
DEPC did not cause strand scissions in the phage DNA, as exhibited by sucrose gradient centrifugation analysis. It changed the serum-blocking power of the phage, and this change was thought to be due to the structural alteration of phage tail-proteins.
The results are discussed in relation to the elimination of active phages from the dairy cultures.
