The influence of water on the resistance of spores to inactivation by gaseous ethylene oxide

Dadd, A. H.; Town, Margaret; McCormick, K. E.

doi:10.1111/j.1365-2672.1985.tb01718.x

Cited by 3 publications

(3 citation statements)

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“…On this model, the ratio of time constants should be Ϸ(577͞177) 2 ϭ 10.6, which is close to the observed ratio, 480 s͞48 s Ϸ 10. Y Various authors have studied the effect of RH on inactivation of bacterial spores by gas-phase ethylene oxide (25), formaldehyde (26,27), and chlorine dioxide [Chlorine Dioxide (ClO 2 ) Gas Phase Demonstration Project, U.S. Environmental Protection Agency Environmental Response Team Report, unpublished]. All of them reported that spore killing efficacy increased with RH, approaching 100% for RH greater than Ϸ70%, but opinions differed as to the role of humidity.…”

Section: Discussionmentioning

confidence: 99%

“…They found that small solutes such as water enter the cell rather easily, with q ϵ 1.0, whereas larger ones encounter more difficulty. Applying their experimental dependence of q on molecular volume to the gases that have been used to inactivate spores (25,(25)(26)(27), we estimate partition ratios q ϭ 0.94, 0.90, and 0.7 for formaldehyde, ethylene oxide, and chlorine dioxide, respectively. Admittedly, these values of q are not much smaller than unity, but they are based on observations in vegetative cells, not spores.…”

Section: Discussionmentioning

confidence: 99%

“…We determined the amplitude of swelling for the particles by comparing the average semimajor or semiminor axes in the 10 measurements before changing humidity (i.e., scans [16][17][18][19][20][21][22][23][24][25] to those between 10 and 20 measurements afterward (i.e., scans 36-45). In Fig.…”

Section: Discussionmentioning

confidence: 99%

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Kinetics of size changes of individual Bacillus thuringiensis spores in response to changes in relative humidity

Westphal

Price

Leighton

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

153

125

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Using an automated scanning microscope, we report the surprising result that individual dormant spores of Bacillus thuringiensis grow and shrink in response to increasing and decreasing relative humidity. We simultaneously monitored the size of inorganic calibration particles. We found that the spores consistently swell in response to increased relative humidity, and shrink to near their original size on reexposure to dry air. Although the dispersion of swelling amplitudes within an ensemble of spores is wide (Ϸ30% of the average amplitude), amplitudes for individual spores are highly correlated between different swelling episodes, suggesting that individual spores respond consistently to changes in humidity. We find evidence for two distinct time scales for swelling: one with a time scale of no more than Ϸ50 s, and another with a time scale of Ϸ8 min. We speculate that these two mechanisms may be due to rapid diffusion of water into the spore coat ؉ cortex, followed by slower diffusion of water into the spore core, respectively. Humidity-dependent swelling may account for the greater kill effectiveness of spores by gas-phase chlorine dioxide, formaldehyde, and ethylene oxide at very high relative humidity. In the aftermath of the anthrax attacks in Fall 2001, we looked into measurable physical properties of bacterial endospores that might distinguish Bacillus anthracis from other species. This led to two striking discoveries: The first, which we report in this paper, is that dormant spores are not entirely static but rapidly swell and shrink in response to increases and decreases in relative humidity (RH), with interesting biological implications. The second, which we report in a subsequent paper, is that, when RH and temperature are held constant, accurate measurements of sizes of Bacillus spores can discriminate among species.It has long been known from the high refractive index of spores that the core has a low water content. Neihof et al.(1) measured water sorption and desorption of both freeze-dried and crushed Bacillus subtilis spores as a function of RH. From the sigmoid shape, hysteresis, and similar behavior of normal and crushed spores, they inferred that swelling accompanies sorption and that an anhydrous spore core is not maintained by a water permeability barrier.Studies of the inverse correlation between spore heat resistance and water content have led to the present view that an osmotic pressure within the spore is responsible for maintaining the partly dry core (2, 3). The requisite tension and pressure are thought to be generated in the cortex by peptidoglycan, initially polymerized in an ordered tightly packed conformation, fixed by cross-linking of the glycan chains (3). From experiments with deuterated water, Marshall and Murrell (4) concluded that at least 97% of the water in spores was able to exchange with the environment. In experiments with tritiated water, they found that water exchange in a population of spores as well as of vegetative cells was almost complete in 2-3 min at 0°C. In m...

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Section: Discussionmentioning

confidence: 99%