Spatially Resolved Characterization of Water and Ion Incorporation in Bacillus Spores

Abstract

We present the first direct visualization and quantification of water and ion uptake into the core of individual dormant Bacillus thuringiensis subsp. israelensis (B. thuringiensis subsp. israelensis) endospores. Isotopic and elemental gradients in the B. thuringiensis subsp. israelensis spores show the permeation and incorporation of deuterium in deuterated water (D 2 O) and solvated ions throughout individual spores, including the spore core. Under hydrated conditions, incorporation into a spore occurs on a time scale of minutes, with subsequent uptake of the permeating species continuing over a period of days. The distribution of available adsorption sites is shown to vary with the permeating species. Adsorption sites for Li ؉ , Cs ؉ , and Cl ؊ are more abundant within the spore outer structures (exosporium, coat, and cortex) relative to the core, while F ؊ adsorption sites are more abundant in the core. The results presented here demonstrate that elemental abundance and distribution in dormant spores are influenced by the ambient environment. As such, this study highlights the importance of understanding how microbial elemental and isotopic signatures can be altered postproduction, including during sample preparation for analysis, and therefore, this study is immediately relevant to the use of elemental and isotopic markers in environmental microbiology and microbial forensics.

Analysis of Metabolism in Dormant Spores of Bacillus Species by 31 P Nuclear Magnetic Resonance Analysis of Low-Molecular-Weight Compounds

“…However, the GR-less spores incubated at elevated temperatures exhibited no evidence of normal early germination events as DPA levels in spores incubated in spent sporulation medium at elevated temperatures did not decrease. Another possibility is that some of the many compounds in the spent sporulation medium permeate into the dormant spore core and alter spore metabolism, and both anions and cations can slowly enter the spore core (35,36). However, permeation of small molecules into spores over periods of weeks at elevated temperatures has not been studied, nor has how such permeation could alter spore metabolism.…”

Water and Small-Molecule Permeation of Dormant Bacillus subtilis Spores

“…All spore compartments contain water, although the core is thought to be only ϳ30% water by weight while outer spore layers are ϳ80% water (17,18). Water does penetrate through the entire spore core, and there are several reports that rates of water movement across the IM are rather low, as is movement of other small molecules into the spore core (1,(18)(19)(20)(21)(22)(23). However, other reports suggest that the barrier to water entry into the spore core is not exclusively the IM (4,9,10,22).…”

Nanomechanical Characterization of Bacillus anthracis Spores by Atomic Force Microscopy

“…The NMR analysis of Bradbury et al (57) indicated that the mobility and concentration of water in the core are higher than those in the coat and cortex. Ghosal et al (58) studied water and ion uptake into the core of dormant Bacillus thuringiensis spores. Using isotopic and elemental gradients in the B. thuringiensis spores, they showed that deuterated water (D 2 O) and solvated ions can permeate throughout and be incorporated into the whole spore.…”