Koch A L
Department of Biology, Indiana University, Bloomington 47405.
J Theor Biol. 1993 Jan 7;160(1):1-21. doi: 10.1006/jtbi.1993.1001.
Bacteria are capable of surviving in a wide range of seemingly impossible situations. In the main part this is because very large numbers of individual cells are involved, so that even very rare mutations will occur often enough to solve most acute problems and permit growth. But in addition, bacteria have evolved in an environment that has fluctuated so often in the past that they may have evolved a group of "last ditch" mechanisms to meet these challenges. These include developing a metabolically inactive state; activating previously evolved, but silent genes; increasing rates of mutation under dire condition; and favoring movement of exogenous and endogenous genetic elements. Some of these processes can function to make it appear that directed "Lamarckian" mutations have occurred. Together these survival mechanisms constitute the "catastrophe insurance" of the cells.
细菌能够在一系列看似不可能的情况下存活。在很大程度上，这是因为涉及到大量的单个细胞，以至于即使是非常罕见的突变也会经常发生，足以解决大多数严峻问题并允许生长。但此外，细菌是在一个过去经常波动的环境中进化而来的，以至于它们可能已经进化出一组“最后手段”机制来应对这些挑战。这些机制包括进入代谢不活跃状态；激活先前进化但处于沉默状态的基因；在极端条件下提高突变率；以及促进外源和内源遗传元件的移动。其中一些过程的作用可能会让人觉得发生了定向的“拉马克式”突变。这些生存机制共同构成了细胞的“灾难保险”。
