RESPONSES OFBACILLUS SUBTILISSPORES TO IONIC ENVIRONMENTS DURING SPORULATION AND GERMINATION

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Abstract
The ionic environments of germination and sporulation menstrua had a prominent influence on characteristics of B. subtilis spores. There was a synergistic effect for L-alanine and inorganic ions on spore germination. The maximal rate of germination in solutions of L-alanine was dependent on ionic concentration and species. Germination was negligible in L-alanine at low ionic strength but increased as the ionic strength was increased up to about 10-1M with a variety of salts. Phosphate was the most active ion tested, and divalent cations were the least active in supporting germination in L-alanine. Germination progressed slowly at 45 C in sodium chloride or sodium phosphate alone but not in CaCl2 alone. Germination rates in L-alanine were retarded at high ionic strengths ([mu] in the range of 0.1 to 1.0). Inhibitory effects of high concentrations of certain divalent cations on germination were related to the binding abilities of these metals. High concentrations of NaCl (10-1 to 1.0 M) in the sporulation medium resulted in lowered heat resistance and germination rate of the resulting spores. The addition of calcium (5xl0-2 MCaCl2) to the sporulation medium relieved the repression of NaCl on germination and caused the spores to have a greater heat resistance. Calcium and dipicolinic acid (DPA) contents of the spores were unaffected by NaCl in the sporulation medium. The calcium, but not the DPA, content of spores increased as a result of supplementing the sporulation medium with calcium. Possible roles of ions in the germination of spores are discussed.