Effect of reciprocal pressurization on germination and killing of bacterial spores

We measured the germinating and inactivating effects of reciprocal pressurization (consisting of six cycles of 5 min compression and rapid decompression) (RP) on bacterial spores compared with the effects of continuous pressurization (CP) by using heat sensitivity (70 degreesC, 30 min) as a criterion for germination. There was no significant difference in the germination of spores by RP and CP, but there was a significant difference in spore inactivation by RP and CP except for 200 MPa-25 and 35 degreesC. The number of germinated spores was more than the number of inactivated spores following RP and CP. These results indicated that compression could initiate germination, whereas rapid decompression could not initiate germination, but could inactivate the germinated spores. Thus, RP was more effective than CP in inactivating spores.