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 examined using Bacillus cereus T spores treated with sodium dodecyl sulfate (SDS) and dithiothreitol (DTT) at pH 10. The first phase of the germination was stimulated by Ca2+ in the concentration-dependent manner, showing the optimal concentration at 0.5-1.0 mM. The second phase appeared to be insensitive to the cation. The optimal temperatures for the first and the second phase were 25 C and 40 C, respectively; the optimal pHs for the two phases were 7-9 and around 7.5, respectively. Heat resistance and dipicolinic acid of the SDS-DTT-treated spores were lost mostly during the first phase. A Ca(2+)-specific chelator, glycoletherdiamine-N,N,N',N'-tetraacetic acid (GEDTA), inhibited the first phase evoked by Ca2+, while it had no inhibitory effect on the second phase. 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+.