Heat Adaptation and Ion Exchange in Bacillus megaterium Spores

Abstract

A new spore phenomenon is described in which induction of increased heat resistance occurs during the process of heating. In buffered environments the acid form of dormant mature bacterial spores shows a temperature dependent adaptation to heat which is correlated with the rate of uptake of Ca(OH)(2) by titration at constant p(H) in neutral salt solution.

Importance of Considering Injured Microorganisms in Sterilization Validation

“…High acidity is linked with the removal of cations, especially calcium, from the spores (Blocher and Busta, 1985;Rode and Foster, 1966), which may cause a reversible injury of the germination mechanism (Gould, 1984) because calcium is an indispensable agent for spore germination (Shintani, 2006). The exchange of cations caused by acid treatment also reduces the heat resistance of the spores (Alderton, 1964), which is also reduced by irradiation resistance (Gomez, 1980). Reduced heat resistance catalyzed by acid is reversed when the spores are reloaded with cations (Gould, 1984).…”

Occurrence of Bacillus subtilis with High Heat Resistance

“…It is quite possible that in evaporated milk the spores of our strain B. subtilis Bac 1-12 could gradually develop increasing heat resistance during the heating, as a slowly evoked protective response within the spores (see Alderton, Thompson & Snell, 1964). These observations are not in agreement with those of Franklin et al (1958) who obtained lower numbers of survivors in milk than in water as well as some acceleration of the spore inactivation in milk by increasing the heating temperature, The phenomenon described by Alderton et al (1964) was later observed by Edwards et al (1965a) and in their experiments it resulted in concave time survivor curves of the spores of B. subtilis strain A with a z value of 16 in the lower temperature range (113"-120") and 33 in the higher temperature range (121"-135"). The same authors observed an increase in surviving spores of B. subtilis strain A, but only in the lower temperature range, when the recovery medium was enriched with Ca2+ and sodium dipicolinate, as mentioned by Doi (1961) and studied in practice by Busta & Ordal (1964).…”

The heat resistance of anaerobic spores in aqueous suspension

“…The present study employed only sealed ampoules, and such an artifact may be fairly confidently eliminated. Alderton, Thompson & Snell (1964) were able to increase the heat resistance of spores of B. rnegaterium by holding spores at sub-lethal temperatures. Survivor curves which are concave upwards may be interpreted in terms of a population resistance which increases during the heat treatment, and although no direct evidence is presented regarding this point in the present study, the possibility of it occurring should not be overlooked.…”