Isken S, de Bont J A
Department of Food Technology and Nutritional Sciences, Wageningen Agricultural University, The Netherlands.
Extremophiles. 1998 Aug;2(3):229-38. doi: 10.1007/s007920050065.
The toxic effects that organic solvents have on whole cells is an important drawback in the application of these solvents in environmental biotechnology and in the production of fine chemicals by whole-cell biotransformations. Hydrophobic organic solvents, such as toluene, are toxic for living organisms because they accumulate in and disrupt cell membranes. The toxicity of a compound correlates with the logarithm of its partition coefficient with octanol and water (log P(ow)). Substances with a log P(ow) value between 1 and 5 are, in general, toxic for whole cells. However, in recent years different bacterial strains have been isolated and characterized that can adapt to the presence of organic solvents. These strains grow in the presence of a second phase of solvents previously believed to be lethal. Different mechanisms contributing to the solvent tolerance of these strains have been found. Alterations in the composition of the cytoplasmic and outer membrane have been described. These adaptations suppress the effects of the solvents on the membrane stability or limit the rate of diffusion into the membrane. Furthermore, changes in the rate of the biosynthesis of the phospholipids were reported to accelerate repair processes. In addition to these adaptation mechanisms compensating the toxic effect of the organic solvents, mechanisms do exist that actively decrease the amount of the toxic solvent in the cells. An efflux system actively decreasing the amount of solvents in the cell has been described recently. We review here the current knowledge about exceptional strains that can grow in the presence of toxic solvents and the mechanisms responsible for their survival.
有机溶剂对全细胞的毒性作用是这些溶剂在环境生物技术以及全细胞生物转化生产精细化学品中的应用的一个重要缺陷。疏水性有机溶剂，如甲苯，对生物体有毒，因为它们会在细胞膜中积累并破坏细胞膜。一种化合物的毒性与其在正辛醇和水之间的分配系数的对数（log P(ow)）相关。log P(ow)值在1到5之间的物质通常对全细胞有毒。然而，近年来已经分离并鉴定出了不同的细菌菌株，它们能够适应有机溶剂的存在。这些菌株能在先前被认为是致命的第二相溶剂存在的情况下生长。已经发现了导致这些菌株具有溶剂耐受性的不同机制。已经描述了细胞质膜和外膜组成的改变。这些适应性变化抑制了溶剂对膜稳定性的影响，或者限制了溶剂扩散进入膜的速率。此外，据报道磷脂生物合成速率的变化会加速修复过程。除了这些补偿有机溶剂毒性作用的适应机制外，确实存在能主动减少细胞内有毒溶剂含量的机制。最近描述了一种能主动减少细胞内溶剂含量的外排系统。我们在此综述关于能在有毒溶剂存在下生长的特殊菌株以及它们存活所涉及机制的当前知识。
