Draghi Jeremy A, Turner Paul E
Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520, USA.
Microbiology (Reading). 2006 Sep;152(Pt 9):2683-2688. doi: 10.1099/mic.0.29013-0.
Natural genetic transformation can facilitate gene transfer in many genera of bacteria and requires the presence of extracellular DNA. Although cell lysis can contribute to this extracellular DNA pool, several studies have suggested that the secretion of DNA from living bacteria may also provide genetic material for transformation. This paper reviews the evidence for specific secretion of DNA from intact bacteria into the extracellular environment and examines this behaviour from a population-genetics perspective. A mathematical model demonstrates that the joint action of DNA secretion and transformation creates a novel type of gene-level natural selection. This model demonstrates that gene-level selection could explain the existence of DNA secretion mechanisms that provide no benefit to individual cells or populations of bacteria. Additionally, the model predicts that any trait affecting DNA secretion will experience selection at the gene level in a transforming population. This analysis confirms that the secretion of DNA from intact bacterial cells is fully explicable with evolutionary theory, and reveals a novel mechanism for bacterial evolution.
自然遗传转化可促进许多细菌属中的基因转移，且需要细胞外DNA的存在。虽然细胞裂解可对这个细胞外DNA库有所贡献，但多项研究表明，活细菌分泌DNA也可能为转化提供遗传物质。本文综述了完整细菌将DNA特异性分泌到细胞外环境的证据，并从群体遗传学角度审视了这种行为。一个数学模型表明，DNA分泌和转化的共同作用产生了一种新型的基因水平自然选择。该模型表明，基因水平选择可以解释那些对单个细胞或细菌群体没有益处的DNA分泌机制的存在。此外，该模型预测，在一个可转化群体中，任何影响DNA分泌的性状都会在基因水平上受到选择。这一分析证实，完整细菌细胞分泌DNA完全可用进化理论解释，并揭示了一种细菌进化的新机制。
