Spores of Bacillus subtilis:: their resistance to and killing by radiation, heat and chemicals
Spores of Bacillus subtilis:: their resistance to and killing by radiation, heat and chemicals
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DOI：
10.1111/j.1365-2672.2005.02736.x
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发表时间：
2006-09-01
影响因子：
4
通讯作者：
Setlow, P.
中科院分区：
文献类型：
--
作者：
Setlow, P.
许多机制导致芽孢杆菌属物种的孢子对热、辐射和化学品的耐受性以及这些试剂杀死孢子的能力。孢子对湿热的抵抗力很大程度上取决于孢子核心的含水量，其远低于生长的细胞原生质体中的含水量。较低的核心水含量通常会产生更多的耐湿热孢子。孢子核心矿物离子的水平和类型以及总孢子蛋白的内在稳定性也在孢子耐湿热性中发挥作用，并且孢子DNA被α/β型小酸溶性孢子蛋白（SASP）饱和可以保护DNA免受湿热损伤。然而，湿热如何杀死孢子尚不清楚，尽管它不是通过DNA损伤来杀死的。 α/β 型 SASP 对于孢子对干热的抵抗力也很重要，就像孢子生长过程中的 DNA 修复一样，枯草芽孢杆菌孢子通过 DNA 损伤被干热杀死。紫外线和伽马辐射也会通过 DNA 损伤杀死孢子。尽管不涉及α/β型SASP，但孢子抵抗γ辐射的机制尚不清楚。相比之下，孢子的紫外线抗性主要是由于α/β型SASP与DNA的结合引起的孢子DNA光化学的改变，并且在较小程度上是由于孢子核心的大量吡啶二羧酸的光敏作用。 254 nm 的紫外线照射孢子不会产生生长细胞中相邻嘧啶之间形成的环丁烷二聚体 (CPD) 和 (6-4)-光产物 (64PP)，而是产生称为孢子光产物 (SP) 的胸苷基-胸苷加合物。虽然 SP 在孢子中形成的量子效率与生长细胞中生成 CPD 和 64PP 的量子效率大致相同，但 SP 在孢子生长过程中通过许多修复系统快速有效地修复，其中至少有一种是 SP 特异性的。一些化学物质（例如亚硝酸、甲醛）再次通过DNA损伤杀死孢子，而其他化学物质，特别是氧化剂，似乎会损坏孢子的内膜，使得该膜在孢子萌发和生长时破裂。还有其他药剂，例如戊二醛，其杀死孢子的机制尚不清楚。孢子耐化学性的重要因素因化学品而异，但包括： (i) 可能与化学试剂发生反应并解毒的孢子外壳蛋白； (ii) 孢子内膜的相对不渗透性，限制了外源化学物质进入孢子核心； (iii)通过用α/β型SASP饱和来保护孢子DNA； (iv) 通过 DNA 损伤杀死孢子的试剂的 DNA 修复。鉴于杀死芽孢杆菌属孢子在食品和医疗产品工业中的重要性，对孢子抵抗和杀死机制的更深入了解可能会导致孢子破坏方法的改进。
A number of mechanisms are responsible for the resistance of spores of Bacillus species to heat, radiation and chemicals and for spore killing by these agents. Spore resistance to wet heat is determined largely by the water content of spore core, which is much lower than that in the growing cell protoplast. A lower core water content generally gives more wet heat-resistant spores. The level and type of spore core mineral ions and the intrinsic stability of total spore proteins also play a role in spore wet heat resistance, and the saturation of spore DNA with alpha/beta-type small, acid-soluble spore proteins (SASP) protects DNA against wet heat damage. However, how wet heat kills spores is not clear, although it is not through DNA damage. The alpha/beta-type SASP are also important in spore resistance to dry heat, as is DNA repair in spore outgrowth, as Bacillus subtilis spores are killed by dry heat via DNA damage. Both UV and gamma-radiation also kill spores via DNA damage. The mechanism of spore resistance to gamma-radiation is not well understood, although the alpha/beta-type SASP are not involved. In contrast, spore UV resistance is due largely to an alteration in spore DNA photochemistry caused by the binding of alpha/beta-type SASP to the DNA, and to a lesser extent to the photosensitizing action of the spore core's large pool of dipicolinic acid. UV irradiation of spores at 254 nm does not generate the cyclobutane dimers (CPDs) and (6-4)-photoproducts (64PPs) formed between adjacent pyrimidines in growing cells, but rather a thymidyl-thymidine adduct termed spore photoproduct (SP). While SP is formed in spores with approximately the same quantum efficiency as that for generation of CPDs and 64PPs in growing cells, SP is repaired rapidly and efficiently in spore outgrowth by a number of repair systems, at least one of which is specific for SP. Some chemicals (e.g. nitrous acid, formaldehyde) again kill spores by DNA damage, while others, in particular oxidizing agents, appear to damage the spore's inner membrane so that this membrane ruptures upon spore germination and outgrowth. There are also other agents such as glutaraldehyde for which the mechanism of spore killing is unclear. Factors important in spore chemical resistance vary with the chemical, but include: (i) the spore coat proteins that likely react with and detoxify chemical agents; (ii) the relative impermeability of the spore's inner membrane that restricts access of exogenous chemicals to the spore core; (iii) the protection of spore DNA by its saturation with alpha/beta-type SASP; and (iv) DNA repair for agents that kill spores via DNA damage.Given the importance of the killing of spores of Bacillus species in the food and medical products industry, a deeper understanding of the mechanisms of spore resistance and killing may lead to improved methods for spore destruction.