Department of Biological Sciences, University of Wisconsin, Milwaukee, Wisconsin 53212, USA.
J Bacteriol. 2011 Jul;193(14):3624-32. doi: 10.1128/JB.00092-11. Epub 2011 May 20.
Xenorhabdus nematophila, the mutualistic bacterium of the nematode Steinernema carpocapsae, produces the R-type bacteriocin called xenorhabdicin, which is thought to confer a competitive advantage for growth in the insect host. We have identified a P2-like tail synthesis gene cluster (xnp1) that is required for xenorhabdicin production. The xnp1 genes were expressed constitutively during growth and were induced by mitomycin C. Deletion of either the sheath (xnpS1) or fiber (xnpH1) genes eliminated xenorhabdicin production. Production of R-type bacteriocins in a host organism had not been shown previously. We show that xenorhabdicin is produced in the hemocoel of insects infected with the wild type but not with the ΔxnpS1 deletion strain. Xenorhabdicin prepared from the wild-type strain killed the potential competitor Photorhabdus luminescens TT01. P. luminescens was eliminated during coculture with wild-type X. nematophila but not with the ΔxnpS1 strain. Furthermore, P. luminescens inhibited reproduction of S. carpocapsae in insect larvae, while coinjection with wild-type X. nematophila, but not the ΔxnpS1, strain restored normal reproduction, demonstrating that xenorhabdicin was required for killing P. luminescens and protecting the nematode partner. Xenorhabdicin killed X. nematophila from Steinernema anatoliense, demonstrating for the first time that it possesses intraspecies activity. In addition, activity was variable against diverse strains of Xenorhabdus and Photorhabdus and was not correlated with phylogenetic distance. These findings are discussed in the context of the role of xenorhabdicin in the life cycle of the mutualistic bacterium X. nematophila.
寡毛实蝇共生菌 X. nematophila 产生的 R 型细菌素称为 Xenorhabdicin，被认为赋予了其在昆虫宿主中生长的竞争优势。我们已经鉴定出一个 P2 样尾合成基因簇（xnp1），该基因簇对于 Xenorhabdicin 的产生是必需的。xnp1 基因在生长过程中持续表达，并被丝裂霉素 C 诱导。鞘（xnpS1）或纤维（xnpH1）基因的缺失均消除了 Xenorhabdicin 的产生。以前尚未显示宿主生物中产生 R 型细菌素。我们表明，在感染野生型的昆虫血腔中产生 Xenorhabdicin，但在感染ΔxnpS1 缺失株的昆虫血腔中不产生。从野生型菌株制备的 Xenorhabdicin 杀死了潜在的竞争者 Photorhabdus luminescens TT01。在与野生型 X. nematophila 共培养时消除了 P. luminescens，但在与ΔxnpS1 菌株共培养时未消除。此外，P. luminescens 抑制了 S. carpocapsae 在昆虫幼虫中的繁殖，而与野生型 X. nematophila 共注射，但不是与ΔxnpS1 菌株共注射，则恢复了正常繁殖，表明 Xenorhabdicin 对于杀死 P. luminescens 和保护线虫伙伴是必需的。Xenorhabdicin 杀死了来自 Steinernema anatoliense 的 X. nematophila，这是首次证明它具有种内活性。此外，对不同的 Xenorhabdus 和 Photorhabdus 菌株的活性是可变的，与系统发育距离无关。这些发现是在共生菌 X. nematophila 生命周期中 Xenorhabdicin 作用的背景下讨论的。
