Skirball Institute Program in Molecular Pathogenesis and Department of Microbiology, New York University Medical Center, New York, NY 10016, USA.
Proc Natl Acad Sci U S A. 2012 Oct 2;109(40):16300-5. doi: 10.1073/pnas.1204615109. Epub 2012 Sep 18.
Staphylococcal pathogenicity islands (SaPIs) carry superantigen and resistance genes and are extremely widespread in Staphylococcus aureus and in other Gram-positive bacteria. SaPIs represent a major source of intrageneric horizontal gene transfer and a stealth conduit for intergeneric gene transfer; they are phage satellites that exploit the life cycle of their temperate helper phages with elegant precision to enable their rapid replication and promiscuous spread. SaPIs also interfere with helper phage reproduction, blocking plaque formation, sharply reducing burst size and enhancing the survival of host cells following phage infection. Here, we show that SaPIs use several different strategies for phage interference, presumably the result of convergent evolution. One strategy, not described previously in the bacteriophage microcosm, involves a SaPI-encoded protein that directly and specifically interferes with phage DNA packaging by blocking the phage terminase small subunit. Another strategy involves interference with phage reproduction by diversion of the vast majority of virion proteins to the formation of SaPI-specific small infectious particles. Several SaPIs use both of these strategies, and at least one uses neither but possesses a third. Our studies illuminate a key feature of the evolutionary strategy of these mobile genetic elements, in addition to their carriage of important genes-interference with helper phage reproduction, which could ensure their transferability and long-term persistence.
葡萄球菌致病性岛（SaPIs）携带超抗原和耐药基因，在金黄色葡萄球菌和其他革兰氏阳性菌中极为普遍。SaPIs 代表了种内水平基因转移的主要来源和种间基因转移的隐蔽渠道；它们是噬菌体卫星，巧妙地利用其温和噬菌体的生命周期，实现快速复制和滥用地传播。SaPIs 还干扰辅助噬菌体的繁殖，阻止噬菌斑的形成，显著减少爆发大小，并增强宿主细胞在噬菌体感染后的存活能力。在这里，我们展示了 SaPIs 使用几种不同的噬菌体干扰策略，这可能是趋同进化的结果。一种策略以前在噬菌体微宇宙中没有描述过，涉及一种由 SaPI 编码的蛋白质，它通过阻断噬菌体终止酶小亚基直接且特异性地干扰噬菌体 DNA 包装。另一种策略涉及通过将绝大多数病毒蛋白转移到 SaPI 特异性小感染性颗粒的形成中来干扰噬菌体的繁殖。几种 SaPIs 使用这两种策略，至少有一种既不使用这两种策略，也不使用第三种策略。我们的研究除了揭示这些移动遗传元件携带重要基因（干扰辅助噬菌体繁殖）这一关键特征外，还阐明了它们的进化策略，这有助于它们的可转移性和长期存在。
