Studies on Germination of Calcium- And Zinc-Enriched Spores of Bacillus Cereus T

Abstract

The calcium-dipicolinic acid (Ca-DPA) complex in the spores of Bacillus cereus T is believed to play an important role in the phenomenon of heat resistance. Studies were carried out to determine whether calcium was present in the form of a complex with DPA. Ca and DPA are known to be released into the medium following germination. The presence of Ca-DPA complex in the spores can be established, if Ca and DPA are released in the same ratio in which they are present in the spores. This was studied by preparing spores having different Ca-DPA ratio, and subsequently determining the ratio in which they were released during germination. The present results indicate that the Ca-DPA ratio during the release was the same as in the spores. Attempts were also made by increasing the Zn concentration in the medium to see whether Zn could replace Ca in Ca-DPA complex. The results obtained show that Zn is not taken up by the spores in the presence of Ca.During the life cycle of spore-forming bacteria there are two important stages, sporulation and germination. During sporulation the bacterial cells are transformed into dormant bodies known as endospores. Endospores are highly refractile and resistant to heat and other deleterious agents. Under favourable conditions they can break their dormancy and become sensitive to heat, leading ultimately to the formation of typical bacterial cells. This process is known as spore germination (1-4). Germination can be measured by release of dipicolinic acid (DPA) (5, 6), and increase in UV resistance (7,8) or by decrease in optical density. Germination of bacterial spores occurs in two phases. Loss of DPA and heat stability from the spores form the first phase of germination. During the second phase macromolecular synthesis occurs (9).It is a well-known fact that ions play an important role in spore germination (10). RODE and FOSTER (11) claimed that nonionic compounds such as