ROLE OF CALCIUM IN BIPHASIC GERMINATION OF BACILLUS-CEREUS T-SPORES SENSITIZED TO LYSOZYME

Biphasic germination induced by inosine in the presence of Ca2+ was ex amined using Bacillus cereus T spores treated with sodium dodecyl sulf ate (SDS) and dithiothreitol (DTT) at pH 10. The first phase of the ge rmination was stimulated by Ca2+ in the concentration-dependent manner , showing the optimal concentration at 0.5-1.0 mM. The second phase ap peared to be insensitive to the cation. The optimal temperatures for t he first and the second phase were 25 C and 40 C, respectively; the op timal pHs for the two phases were 7-9 and around 7.5, respectively. He at resistance and dipicolinic acid of the SDS-DTT-treated spores were lost mostly during the first phase. A Ca2+-specific chelator, glycolet herdiamine-N,N,N',N'-tetraacetic acid (GEDTA), inhibited the first pha se evoked by Ca2+, while it had no inhibitory effect on the second pha se. In contrast, the divalent cations examined, except Mg2+ and Sr2+, affected not only the first phase but also the second phase. The order of inhibitory effect on the first phase was Hg2+ > Zn2+ > Ba2+, Co2+, Cu2+ > Mn2+; on the second phase, it was Hg2+ > Cu2+ > Zn2+ > Co2+ > Mn2+ > Ba2+.