Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK Department of Microbiology, University College Cork, Cork, Ireland.
Environ Microbiol. 2012 Apr;14(4):953-66. doi: 10.1111/j.1462-2920.2011.02669.x. Epub 2011 Dec 12.
The bacterium, Photorhabdus luminescens, is an insect pathogen that also maintains a mutualistic interaction with nematodes from the family Heterorhabditis. Photorhabdus luminescens is carried in the gut of the infective juvenile (IJ), a nematode stage that infects soft-cuticled insect larvae in the soil. Photorhabdus luminescens is released into the insect blood to convert the insect into a biomass that is able to support nematode growth and development. Nematode reproduction continues for 2-3 generations before the nematodes enter an alternative developmental pathway leading to a new generation of IJs that are efficiently colonized by P. luminescens in a process called transmission. Transmission begins with the adherence of P. luminescens to the rectal gland cells (RGC) located in the gut of the hermaphrodite. The bacteria enter, and replicate within, the RGC resulting in vacuolization, and ultimately lysis, of the RGC. In this way P. luminescens are released throughout the body cavity of the hermaphrodite to encounter, and colonize, the developing IJs. In this study we show that the LysR-type regulator, HdfR, is required for normal transmission in P. luminescens TTO1. Transcriptome analysis revealed that HdfR regulates the expression of 124 genes, including genes involved in arginine metabolism, hydroxyphenylacetate catabolism and pigment production. Using fluorescence microscopy we show that the ΔhdfR mutant is able to attach to, and grow within, the hermaphrodite as well as wild-type bacteria but subsequent steps in transmission are delayed. Therefore, HdfR plays an important role in coordinating the interaction between P. luminescens and its nematode partner during transmission.
发光杆菌是一种昆虫病原体，它与异小杆线虫科的线虫维持着共生关系。发光杆菌存在于感染性幼虫（IJ）的肠道中，IJ 是一种感染土壤中软壳昆虫幼虫的线虫阶段。发光杆菌被释放到昆虫血液中，将昆虫转化为一种能够支持线虫生长和发育的生物质。线虫繁殖继续进行 2-3 代，然后线虫进入另一种发育途径，导致新一代 IJ 进入，这些 IJ 被发光杆菌有效地殖民，这一过程称为传播。传播始于发光杆菌与位于雌雄同体肠道中的直肠腺细胞（RGC）的粘附。细菌进入并在 RGC 内复制，导致 RGC 空泡化，并最终裂解。通过这种方式，发光杆菌被释放到雌雄同体的体腔中，以遇到并殖民正在发育的 IJ。在这项研究中，我们表明 LysR 型调控因子 HdfR 是发光杆菌 TTO1 正常传播所必需的。转录组分析显示，HdfR 调节 124 个基因的表达，包括参与精氨酸代谢、对羟基苯乙酸分解代谢和色素产生的基因。通过荧光显微镜观察，我们发现Δ hdfR 突变体能附着在雌雄同体上并在其中生长，与野生型细菌一样，但随后的传播步骤被延迟。因此，HdfR 在协调发光杆菌与其线虫伙伴在传播过程中的相互作用方面发挥着重要作用。
