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Atomistic Study of Wet-heat Resistance of Calcium Dipicolinate in the Core of Spores

Published online by Cambridge University Press:  15 January 2018

Ankit Mishra*
Affiliation:
Collaboratory for Advanced Computing and Simulations, University of Southern California, Los Angeles, CA90089
Pankaj Rajak
Affiliation:
Collaboratory for Advanced Computing and Simulations, University of Southern California, Los Angeles, CA90089
Subodh Tiwari
Affiliation:
Collaboratory for Advanced Computing and Simulations, University of Southern California, Los Angeles, CA90089
Chunyang Sheng
Affiliation:
Collaboratory for Advanced Computing and Simulations, University of Southern California, Los Angeles, CA90089
Aravind Krishnamoorthy
Affiliation:
Collaboratory for Advanced Computing and Simulations, University of Southern California, Los Angeles, CA90089
Aiichiro Nakano
Affiliation:
Collaboratory for Advanced Computing and Simulations, University of Southern California, Los Angeles, CA90089
Rajiv Kalia
Affiliation:
Collaboratory for Advanced Computing and Simulations, University of Southern California, Los Angeles, CA90089
Priya Vashishta
Affiliation:
Collaboratory for Advanced Computing and Simulations, University of Southern California, Los Angeles, CA90089
*
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Abstract

The extreme heat resistance of dormant bacterial spores strongly depends on the extent of protoplast dehydration and the concentration of dipicolinic acid (DPA) and its associated calcium salts (Ca-DPA) in the spore core. Recent experiments have suggested that this heat resistance depends on the properties of confined water molecules in the hydrated Ca-DPA-rich protoplasm, but atomistic details have not been elucidated. In this study, we used reactive molecular dynamics (RMD) simulations to study the dynamics of water in hydrated DPA and Ca-DPA as a function of temperature. The RMD simulations indicate two distinct solid-liquid and liquid-gel transitions for the spore core. Simulation results reveal monotonically decreasing solid-gel-liquid transition temperatures with increasing hydration. Additional calculations on the specific heat and free energy of water molecules in the spore core further support the higher heat resistance of dehydrated spores. These results provide an insight into the experimental trend of moist-heat resistance of bacterial spores and reconciles previous conflicting experimental findings on the state of water in bacterial spores.

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Articles
Copyright
Copyright © Materials Research Society 2018 

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References

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