Rowbury Robin J
Sci Prog. 2003;86(Pt 3):157-78. doi: 10.3184/003685003783238662.
A major aim in many areas of microbiology is to ensure sterility, and even where this is impossible, to reduce the number of viable organisms occurring in particular environments to an absolute minimum. This applies in the aquatic environment, where e.g. water treatment must ensure as complete absence of viable microbes as possible. It is also crucial in food processing and production; many food constituents contain appreciable numbers of viable organisms, even potential pathogens, and the number must be greatly reduced and in many situations, the presence of viable organisms totally abolished. Cleaning of food production components and surfaces must also kill associated microbes. In domestic, hospital and commercial situations, similar disinfection is critical. Ultimately, the aim is to ensure, if possible, sterility, with the assurance that microbial problems cannot occur if organisms are absent. Additionally, however, it has been implicitly assumed that killed organisms and even killed cultures cannot (except in minor and trivial ways) influence the behaviour of living organisms that later enter the environment. The work reviewed here challenges that view and in fact disproves it. The findings described show that killed enterobacterial cultures, which prior to killing had phenotypically gained the ability to resist potentially lethal stresses, can pass on such ability to living organisms that later enter their environment i.e. that such killed cultures can convey a baleful legacy to living ones. This phenomenon is so widespread that it is clear that it has significance for enterobacterial survival in natural waters, in foods and in food production, in the domestic, commercial and hospital situation, and in the animal and human body. In fact, in this last area, the likely effect of killed cultures appears to be of appreciable public health importance. Here, the ability of appropriate killed cultures to transfer tolerance to acidity, alkalinity and thermal stress is described, as well as their ability to pass on sensitisation to acid and alkali. Other work reviewed suggests that killed cultures can almost certainly transfer the ability to tolerate hydrogen peroxide, ultraviolet irradiation and metal ions. The serious implications of this phenomenon are further emphasised by the fact that numerous killing methods produce cultures effective in tolerance response transfer. All the evidence suggests that it is extracellular components (extracellular sensing components, ESCs, and extracellular induction components, EICs), in the killed cultures which are involved in stress response transfer, and that the actual stress response induction process depends on interaction of living organisms with EICs from the killed cultures. It is of note that ESCs and EICs survive in killed cultures because of their extreme resistance to irreversible inactivation by lethal levels of stressing agents and conditions. This is in contrast to the fact that EC activation, namely the conversion of ESC to EIC occurs on exposure to very low levels of stressors. Not only is this the case, but in fact high levels of stressors (e.g. those that kill organisms) generally fail to convert ESC to EIC.
微生物学许多领域的一个主要目标是确保无菌状态，即使在无法实现无菌的情况下，也要将特定环境中活生物体的数量降至绝对最低。这适用于水生环境，例如水处理必须确保尽可能完全不存在活微生物。这在食品加工和生产中也至关重要；许多食品成分含有大量活生物体，甚至潜在病原体，必须大幅减少其数量，在许多情况下，要完全消除活生物体的存在。食品生产部件和表面的清洁也必须杀灭相关微生物。在家庭、医院和商业环境中，类似的消毒至关重要。最终目标是尽可能确保无菌，确保如果没有生物体就不会出现微生物问题。然而，此外，一直隐含地假定死亡的生物体甚至死亡的培养物不会（除了以微小和琐碎的方式）影响后来进入该环境的活生物体的行为。这里所综述的研究对这一观点提出了挑战，实际上予以了反驳。所描述的研究结果表明，在被杀灭之前表型上获得了抵抗潜在致命应激能力的死亡肠杆菌培养物，能够将这种能力传递给后来进入其环境的活生物体，即这种死亡培养物能够给活生物体留下有害的遗产。这种现象非常普遍，显然对肠杆菌在天然水体、食品及食品生产、家庭、商业和医院环境以及动物和人体中的生存具有重要意义。事实上，在最后这个领域，死亡培养物的可能影响似乎对公共卫生具有相当重要的意义。这里描述了适当的死亡培养物传递对酸度、碱度和热应激耐受性的能力，以及它们传递对酸和碱敏感性的能力。所综述的其他研究表明，死亡培养物几乎肯定能够传递耐受过氧化氢、紫外线照射和金属离子的能力。这一现象的严重影响进一步被以下事实所强调，即众多杀灭方法产生的培养物在耐受反应传递方面是有效的。所有证据表明，参与应激反应传递的是死亡培养物中的细胞外成分（细胞外传感成分，ESCs，和细胞外诱导成分，EICs），并且实际的应激反应诱导过程取决于活生物体与来自死亡培养物的EICs之间的相互作用。值得注意的是，ESCs和EICs在死亡培养物中得以存活，是因为它们对致死水平的应激剂和条件导致的不可逆失活具有极强的抵抗力。这与以下事实形成对比，即EC激活，即ESC向EIC的转化，在暴露于极低水平的应激源时就会发生。不仅如此，实际上高水平的应激源（例如那些杀死生物体的应激源）通常无法将ESC转化为EIC。
