Spore heat resistance and specific mineralization

Abstract

to fully demineralized, but viable, H forms by controlled acid titration. H forms were more heat sensitive than were native forms, but z values were greater for killing of H spores than those for native spores. Therefore, the differences in heat sensitivity between native and H forms decreased with increasing killing temperature. The increase in heat sensitivity associated with demineralization did not appear to be due to damage to cortex lytic enzymes of the germination system because it could not be moderated by decoating heated H spores and plating them on medium with added Iysozyme. H spores could be remineralized by means of back titration with appropriate base solutions. The remineralized spores, except for the Na form, were then more heat resistant than were H spores. Ca and Mn were more effective in restoring resistance than were Mg and K. Generally, the remineralized forms (except for the Na form) had z values greater than those of the native forms but still less than those of the H forms. At lower killing temperatures, the reinstatement of resistance could be related to the extent of remineralization. However, at higher killing temperatures, only a fraction of the mineral was effective in restoring resistance, and higher levels of remineralization did not result in greater resistance. Mineralization is clearly an important factor in spore heat resistance, but the relationship between resistance and mineralization is complex and dependent on killing temperature.

Spores of Bacillus subtilis: their resistance to and killing by radiation, heat and chemicals

“…While some of the latter effect may be due to a decrease in core water content with increasing mineralization, the nature of the mineral ions in the core is also important. Although studies have not been extensive, available data indicate that spores with high Ca 2+ levels are most wet heat resistant, spores with high levels of Mg 2+ or Mn 2+ are less heat resistant, and spores in which K + or Na + have been substituted for Ca 2+ are the least wet heat resistant (Bender and Marquis 1985;Gerhardt and Marquis 1989). Other than affecting levels of core water, it is not clear why spore core mineralization and the specific nature of the mineral ions would affect spore wet heat resistance.…”

Mineralization and responses of bacterial spores to heat and oxidative agents

“…The best means to manipulate spore mineral contents is through ion-exchange, as first described by Alderton and Snell [9], In subsequent studies, Bender and Marquis [10] developed procedures for controlled total mineral exchange of a variety of spore types. The procedures allowed for total removal of minerals in acidified media and total replacement with a range of desired minerals, all without any reduction in the viability of the populations used.…”

“…Bender and Marquis [10] concluded from an extensive series of experiments that the hierarchy for protection against moist heat damage for Bacillus megaterium ATCC 19213, Bacillus subtilis niger and Bacillus stearothermophilus ATCC 7953 was Ca > Mn > Mg > K. H and Na appeared to be ineffective for protection. The minerals tested were those normally found in quantity in native spores.…”

Presence of calmodulin-like calcium-binding protein in Bacillus cereus T spores

“…This study first indicates the presence of a calcium-binding protein which possesses some calmodulin-like characteristics in bacterial spores. Similarities to calmodulin included (1) heat stability (2) calcium-dependent binding to hydrophobic interaction chromatography resins and (3) calcium-dependent binding to affinity columns prepared using calmodulin antagonists and (4) reaction in a radioimmunoassay dependent upon antibody to brain calmodulin.…”

“…Accumulation of calcium during sporulation in Bacillus is required for formation of bacterial spores which have normal, high, heat resistance [1][2][3][4]. Additionally, CaC12 can activate B. cereus T spores [5][6][7] and calcium can cause germination if the spore coat is removed or weakened [8].…”