Center for Models of Life, Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen Ø, Denmark.
J Virol. 2011 Oct;85(20):10554-60. doi: 10.1128/JVI.05222-11. Epub 2011 Aug 3.
Bacteria have evolved diverse defense mechanisms that allow them to fight viral attacks. One such mechanism, the clustered, regularly interspaced, short palindromic repeat (CRISPR) system, is an adaptive immune system consisting of genetic loci that can take up genetic material from invasive elements (viruses and plasmids) and later use them to reject the returning invaders. It remains an open question how, despite the ongoing evolution of attack and defense mechanisms, bacteria and viral phages manage to coexist. Using a simple mathematical model and a two-dimensional numerical simulation, we found that CRISPR adaptive immunity allows for robust phage-bacterium coexistence even when the number of virus species far exceeds the capacity of CRISPR-encoded genetic memory. Coexistence is predicted to be a consequence of the presence of many interdependent species that stress but do not overrun the bacterial defense system.
细菌已经进化出多种防御机制，使它们能够抵御病毒攻击。其中一种机制是成簇、规律间隔、短回文重复序列（CRISPR）系统，这是一种适应性免疫系统，由能够摄取来自入侵元素（病毒和质粒）的遗传物质的遗传基因座组成，然后利用这些物质来抵御再次入侵的外来物质。尽管攻击和防御机制在不断进化，但细菌和病毒噬菌体是如何设法共存的，这仍然是一个悬而未决的问题。通过使用简单的数学模型和二维数值模拟，我们发现，即使病毒种类的数量远远超过 CRISPR 编码的遗传记忆能力，CRISPR 适应性免疫也可以允许噬菌体和细菌稳定共存。共存是由于存在许多相互依存的物种而导致的，这些物种对细菌防御系统施加压力，但不会使其崩溃。
