Water is a preservative of microbes.
Water is a preservative of microbes.
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DOI：
10.1111/1751-7915.13980
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发表时间：
2022-01
影响因子：
5.7
通讯作者：
Hallsworth JE
中科院分区：
文献类型：
--
作者：
Hallsworth JE
水是细胞环境，驱动地球生物圈内的所有生物化学，并促进微生物介导的腐烂过程。本文没有回顾这些主题，而是重点关注水作为防腐剂的活性——它维持微生物细胞长期完整性和活力的能力——并确定了发生这种情况的机制。水提供并维持细胞结构；在不同尺度上缓冲热力学极端情况；可以减轻对细胞膜造成损伤的事件，例如干燥-补水、冻融和热冲击；防止微生物脱水，否则会加剧氧化损伤；减轻杀菌因素（在某些情况下减少紫外线辐射并稀释溶质应激源或有毒物质）；并可有效进行静电屏蔽，从而防止某些离子的强静电场对电池造成损坏。此外，干燥细胞中保留的水（历史上称为“结合”水）在生物大分子结构及其相互作用中发挥着关键作用，即使对于完全水合的细胞也是如此。假设细胞膜的成分是化学稳定的或至少是可修复的，并且环境相当恒定，只要这些构型代表热力学稳定状态，水分子显然可以在很长一段时间内保持膜的几何形状。许多微生物的孢子和营养细胞在气相水存在下（中等到高相对湿度）比在更干旱的条件下存活时间更长。有几种机制可以使大片水体在零度以下的天气条件下冷却时保持液态，从而防止其微生物组发生潜在危险（冻融）转变。根据经过数年至数十年进行的实验室研究，微生物生命可以保存在纯水、淡水系统、海水、盐水、冰/永久冻土、富含糖的水环境和气相水中，并且一些自然环境已经产生了明显数千年甚至数亿年（对于矿化氯化钠的高盐流体包裹体）的细胞。防腐剂一词通常仅限于用于延长食品保质期的物质（例如苯甲酸钠、亚硝酸盐和亚硫酸盐）或用于保存死亡生物的物质，例如乙醇或甲醛。然而，对于活的微生物来说，最终的防腐剂实际上可能是水。参考嗜盐菌、人类病原体和其他微生物的生态学讨论了这一作用的影响；食品科学；生物技术；生命和天体生物学其他方面的生物特征；以及全球气候变化引起的保存微生物的大规模释放/重新激活。水作为防腐剂，可以通过多种机制维持微生物细胞的长期完整性和活力。假设细胞膜的成分是化学稳定的，或者至少是可修复的，并且环境相当恒定，只要这些构型代表热力学稳定状态，水分子显然可以在很长一段时间内保持膜的几何形状。目前，全球气候变化正在导致保存的微生物的大规模释放/重新激活。
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 carried out over periods of years to decades and some natural environments that have yielded cells that are apparently thousands, or even (for hypersaline fluid inclusions of mineralized NaCl) hundreds of millions, of years old. The term preservative has often been restricted to those substances used to extend the shelf life of foods (e.g. sodium benzoate, nitrites and sulphites) or those used to conserve dead organisms, such as ethanol or formaldehyde. For living microorganisms however, the ultimate preservative may actually be water. Implications of this role are discussed with reference to the ecology of halophiles, human pathogens and other microbes; food science; biotechnology; biosignatures for life and other aspects of astrobiology; and the large‐scale release/reactivation of preserved microbes caused by global climate change. Water acts as a preservative that can to maintain the long‐term integrity and viability of microbial cells, and does this via a variety of mechanisms. 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. Currently, a large‐scale release/reactivation of preserved microbes is being caused by global climate change.
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