Water is a preservative of microbes

• Published in: Microbial Biotechnology
• Main Author: John E. Hallsworth
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2022
• Subjects: Biotechnology; TP248.13-248.65; Ice; permafrost
• Online Access: https://doi.org/10.1111/1751-7915.13980; https://doaj.org/article/ecb376fd7e9e4bfea67e20ac8846c7b3

Summary Water is the cellular milieu, drives all biochemistry within Earth’s biosphere and facilitates microbe‐mediated decay processes. Instead of reviewing these topics, the current article focuses on the activities of water as a preservative—its capacity to maintain the long‐term integrity and viability of microbial cells—and identifies the mechanisms by which this occurs. Water provides for, and maintains, cellular structures; buffers against thermodynamic extremes, at various scales; can mitigate events that are traumatic to the cell membrane, such as desiccation–rehydration, freeze–thawing and thermal shock; prevents microbial dehydration that can otherwise exacerbate oxidative damage; mitigates against biocidal factors (in some circumstances reducing ultraviolet radiation and diluting solute stressors or toxic substances); and is effective at electrostatic screening so prevents damage to the cell by the intense electrostatic fields of some ions. In addition, the water retained in desiccated cells (historically referred to as ‘bound’ water) plays key roles in biomacromolecular structures and their interactions even for fully hydrated cells. Assuming that the components of the cell membrane are chemically stable or at least repairable, and the environment is fairly constant, water molecules can apparently maintain membrane geometries over very long periods provided these configurations represent thermodynamically stable states. The spores and vegetative cells of many microbes survive longer in the presence of vapour‐phase water (at moderate‐to‐high relative humidities) than under more‐arid conditions. There are several mechanisms by which large bodies of water, when cooled during subzero weather conditions remain in a liquid state thus preventing potentially dangerous (freeze–thaw) transitions for their microbiome. Microbial life can be preserved in pure water, freshwater systems, seawater, brines, ice/permafrost, sugar‐rich aqueous milieux and vapour‐phase water according to laboratory‐based studies ...