COMPARATIVE-STUDY OF PRESSURE-INDUCED GERMINATION OF BACILLUS-SUBTILIS SPORES AT LOW AND HIGH-PRESSURES

We have studied pressure-induced germination of Bacillus subtilis spor es at moderate (100 MPa) and high (500 to 600 MPa) pressures. Although we found comparable germination efficiencies under both conditions by using heat sensitivity as a criterion for germination, the sensitivit y of pressure-germinated spores to some other agents was found to depe nd on the pressure used. Spores germinated at 100 MPa were more sensit ive to pressure (>200 MPa), UV light, and hydrogen peroxide than were those germinated at 600 MPa, Since small, acid-soluble proteins (SASPs ) and dipicolinic acid (DPA) are known to be involved in spore resista nce to UV light and hydrogen peroxide, we studied the fate of these co mpounds during pressure germination. DPA was released upon both low- a nd high-pressure germination, but SASP degradation, which normally acc ompanies nutrient induced germination, occurred upon low-pressure germ ination but not upon high-pressure germination. These results adequate ly explain the UV and hydrogen peroxide resistance of spores germinate d at 600 MPa, The resistance to pressure inactivation of 600-MPa-germi nated spores could also, at least partly, be attributed to alpha/beta- type SASPs, since mutants deficient in alpha/beta-type SASPs were more sensitive to inactivation at 600 MPa. Further, germination at 100 MPa resulted in rapid ATP generation, as is the case in nutrient-induced germination, but no ATP was formed during germination at 600 MPa, Thes e results suggest that spore germination can be initiated by low- and high-pressure treatments but is arrested at an early stage in the latt er case, The implications for the use of high pressure as a preservati on treatment are discussed.