Friedline AW, Zachariah MM, Johnson K, Thomas KJ, Middaugh AN, Garimella R, Powell DR, Vaishampayan PA, Rice CV. Water behavior in bacterial spores by deuterium NMR spectroscopy.
J Phys Chem B 2014;
118:8945-55. [PMID:
24950158 PMCID:
PMC4216197 DOI:
10.1021/jp5025119]
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Abstract
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Dormant bacterial spores are able
to survive long periods of time
without nutrients, withstand harsh environmental conditions, and germinate
into metabolically active bacteria when conditions are favorable.
Numerous factors influence this hardiness, including the spore structure
and the presence of compounds to protect DNA from damage. It is known
that the water content of the spore core plays a role in resistance
to degradation, but the exact state of water inside the core is a
subject of discussion. Two main theories present themselves: either
the water in the spore core is mostly immobile and the core and its
components are in a glassy state, or the core is a gel with mobile
water around components which themselves have limited mobility. Using
deuterium solid-state NMR experiments, we examine the nature of the
water in the spore core. Our data show the presence of unbound water,
bound water, and deuterated biomolecules that also contain labile
deuterons. Deuterium–hydrogen exchange experiments show that
most of these deuterons are inaccessible by external water. We believe
that these unreachable deuterons are in a chemical bonding state that
prevents exchange. Variable-temperature NMR results suggest that the
spore core is more rigid than would be expected for a gel-like state.
However, our rigid core interpretation may only apply to dried spores
whereas a gel core may exist in aqueous suspension. Nonetheless, the
gel core, if present, is inaccessible to external water.
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