Physical Properties of Water in Spores of Bacillus Megaterium

Abstract

Several physical properties of spores of Bacillus megaterium, such as vapor pressure isotherm, complex dielectric constant, nuclear magnetic resonance absorption spectrum, as well as water sorption and desorption rates, were studied in comparison with those of vegetative cells of the same organism with respect to content and form of the cell water. Spores showed larger water content as compared with vegetative cells in the humidity range of less than 78% (R. H.) at 30°, while they showed smaller water content over more humid ranges up to 100% (R. H.). Spores showed a smaller dielectric loss at a microwave frequency of 10 Gc and a broader NMR absorption pattern than vegetative cells. These facts are discussed briefly in terms of molecular motion of the cell water in spores and vegetative cells. Dormant spores of bacteria have higher resistance to heating and chemical treatments than their vegetative forms. Various types of study have been made by a number of investigators on these characteristic features of spores. Studies on the content and form of water in spores are among others.However, different conclusions have been obtained by different investigators, and no satisfactory relation has yet been established between the high resistivity and the state of water molecules in spores.It has been reported by many workers that bacterial spores have lower water content than vegetative cells. For example, POWELL and STRANGE (1) gave this result from the measurement of density and volume of spores, WALDHAM and HALVORSON (2) from isothermal adsorption curves for water vapor, and Ross and BILLIN X (3) from the measurement of refractive index of spores. In this connection, L Jwis, S' LL and BURR (4) proposed the hypothesis that the low water content of spores may result from the contraction of the spore cortex during the spore maturation.On the other hand, H ~N Y and F zl °) V1AN (5, 6) noted that the difference in water content between spores and vegetative cells is not sufficiently great to explain the resistivity of spores. They concluded from their cry-217

Effects of hydration on molecular mobility in phase-bright Bacillus subtilis spores

“…Determination and quantification of water content in spores has been extensively carried out by NMR. Vegetative cells showed narrower absorption peaks in NMR spectra than spores, indicating that water molecules in spores lack mobility in their rotational and\or exchange motions (Maeda et al, 1968). In the same study, no differences in the time course of water absorption and desorption were found between spores and vegetative cells, which suggested that immobilized water molecules could be driven off IP: 52.183.12.225…”

(Symposium on Bacterial Spores : Paper IX). Biophysical Analysis of the Spore

“…4(a) and (a). The curves are typically a, value sigmoid and similar to those for proteins (Bull, 1944) and to those previously obtained for spores (Waldham & Halvomn, 1954;Neihof et al, 1967;Maeda et al, 1968).…”

The physical state of water in bacterial spores

“…Dielectric permittivity data (11) and electron paramagnetic resonance spectra (12) suggest that most ions in the core are immobilized, 13 C NMR spectroscopy indicates that the core's large depot of pyridine-2,6-dicarboxylic acid (dipicolinic acid, DPA) is in a solid-like state (13), and fluorescence measurements show that green fluorescent protein is at least 4 orders of magnitude less mobile in the dormant core than in the cytoplasm of the vegetative B. subtilis cell (14). Although these observations are consistent with a glassy core, attempts using 1 H NMR linewidths to directly measure water mobility in spores have not been conclusive (15,16), partly because of the confounding effect of paramagnetic Mn(II) ions.…”