Grayson Paul, Molineux Ian J
Department of Physics, California Institute of Technology, Pasadena, CA 91125, United States.
Curr Opin Microbiol. 2007 Aug;10(4):401-9. doi: 10.1016/j.mib.2007.04.004. Epub 2007 Aug 21.
The double-stranded DNA inside bacteriophages is packaged at a density of approximately 500 mg/ml and exerts an osmotic pressure of tens of atmospheres. This pressure is commonly assumed to cause genome ejection during infection. Indeed, by the addition of their natural receptors, some phages can be induced in vitro to completely expel their genome from the virion. However, the osmotic pressure of the bacterial cytoplasm exerts an opposing force, making it impossible for the pressure of packaged DNA to cause complete genome ejection in vivo. Various processes for complete genome ejection are discussed, but we focus on a novel proposal suggesting that the osmotic gradient between the extracellular environment and the cytoplasm results in fluid flow through the phage virion at the initiation of infection. The phage genome is thereby sucked into the cell by hydrodynamic drag.
噬菌体内部的双链DNA以约500毫克/毫升的密度进行包装，并施加数十个大气压的渗透压。通常认为这种压力会在感染期间导致基因组释放。实际上，通过添加它们的天然受体，一些噬菌体在体外可以被诱导从病毒体中完全排出其基因组。然而，细菌细胞质的渗透压会产生相反的力，使得包装DNA的压力在体内不可能导致基因组完全释放。文中讨论了多种实现基因组完全释放的过程，但我们重点关注一个新的提议，即细胞外环境与细胞质之间的渗透梯度会在感染开始时导致流体流过噬菌体病毒体。噬菌体基因组因此通过流体动力拖曳被吸入细胞。
