The Effect of Water Activity and the a_w Controlling Solute on Spore Germination of Bacillus stearothermophilus

Abstract

The germination of spores of Bacillus stearothermophilus was studied in nutrient broth in relation to the water activity (a,.,) of the medium, the nature of the a, controlling solutes glycerol, sucrose, KCI, and NaCI, and temperature. Quantitation of germination was based on the change of the phase-bright spore to phase-dark. Activation of spores was by exposure to 100°C/10 min in a medium of the same composition as that used for germination.Of the four solutes used, sucrose proved most inhibitory to germination, especially in the upper part of the temperature range 38-75"C, glycerol was the most favourable whereas KCI and NaCI, whose effect was almost identical, occupied an intermediate place. The glycerol effect became more pronounced as the a, of the medium decreased towards 0.960, becoming inhibitory thereafter.The solute effect on spore germination followed a pattern that related to the class of solute, i.e. electrolyte or non-electrolyte, and its cell penetration characteristics.Solute penetration during heat activation and germination was considered as the major germination. factor and was associated with the osmoregulation mechanism within the spore proposed recently as the basis of spore dormancy and resistance.

How to make a spiral bacterium

“…The mechanical mechanism proposed here for altering shape between spiral and non-spiral forms could be operating in many types of cells that are helically wound with stretch-resistant or contractile fibers. For example, the mechanism we propose can explain why curved-rod bacteria such as C. crescentus (Fischer et al 2002, Wortinger et al 1998 and V. cholerae (Buddelmeijer et al 2002) become spirals as they lengthen when starved, and why multicellular filaments of many species of bacteria wrap around themselves to form supercoiled structures (Anagnostopoulus and Sidhu 1979, Hernandez-Muniz and Stevens 1988, Janssen et al 1991, Mendelson 1976, Mendelson et al 1995.…”

“…However, certain strains, or mutants, of some species form chains of cells that do not separate upon replication. These multicellular filaments, under particular growth conditions, take on a spiral form and wrap around themselves to produce super-coiled structures reminiscent of tangled telephone cords; examples are Bacillis subtilis (Mendelson 1976, Mendelson et al 1995, Bacillus stearothermophilus (Anagnostopoulus and Sidhu 1979), Mastigocladus laminosus (Hernandez-Muniz and Stevens 1988) and Thermus sp. (Janssen et al 1991) (figure 1).…”

Manipulation of intracellular glycerol and erythritol enhances germination of conidia at low water availability

“…Glycerol can act as an exogenous source of compatible solute that enters the cell and reduces the physiological impact of low water availability. In studies of bacterial spore germination, Anagnostopoulos & Sidhu 1981 and Botha & Holzapfel 1988 found that glycerol favoured germination at reduced a w relative to NaCl. This suggests that exogenous glycerol can enhance germination of microbial propagules at reduced a w .…”

Heat-sensitizing effects of plant extracts on Clostridium spp. spores

“…The influence of water activity-depressing solute like NaCl on the thermal resistance of microorganisms such as those observed in this study is similar to those of Coroller, Leguérinel, and Mafart (2001) who reported increased thermal resistance of Bacillus cereus spores in suspending medium containing solutes. Anagnastopoulos and Didhu (1981) and Coroller et al (2001) explained that the presumed protective mechanism rendered by solutes to spores is through the inhibition of spore germination during heating. Since hydration of spore is an important requisite of activation and germination, the presence of water-binding solutes prevents spores from germinating into the more sensitive vegetative cells during heating.…”