Photorhabdus spp. (Enterobacteriales: Morganellaceae) occur exclusively as symbionts of Heterorhabditis nematodes for which they provide numerous services, including killing insects and providing nutrition and defence within the cadavers. Unusually, two species (Photorhabdus cinerea and Photorhabdus temperata) associate with a single population of Heterorhabditis downesi at a dune grassland site. Building on previous work, we investigated competition between these two Photorhabdus species both at the regional (between insects) and local (within insect) level by trait comparison and co-culture experiments. There was no difference between the species with respect to supporting nematode reproduction and protection of cadavers against invertebrate scavengers, but P. cinerea was superior to P. temperata in several traits: faster growth rate, greater antibacterial and antifungal activity and colonisation of a higher proportion of nematodes in co-culture. Moreover, where both bacterial symbionts colonised single nematode infective juveniles, P. cinerea tended to dominate in numbers. Differences between Photorhabdus species were detected in the suite of secondary metabolites produced: P. temperata produced several compounds not produced by P. cinerea including anthraquinone pigments. Bioluminescence emitted by P. temperata also tended to be brighter than that from P. cinerea. Bioluminescence and pigmentation may protect cadavers against scavengers that rely on sight. We conclude that while P. cinerea may show greater local level (within-cadaver) competitive success, co-existence of the two Photorhabdus species in the spatially heterogeneous environment of the dunes is favoured by differing specialisations in defence of the cadaver against differing locally important threats.

光杆状菌。（肠杆菌科：Morganellaceae）仅作为线虫异形线虫的共生体存在，为此它们提供了许多服务，包括杀死昆虫并在尸体内提供营养和防御作用。与众不同的是，两个物种（光杆状菌和光杆状temperata）的协调与对单个群体异小downesi在沙丘草原网站。在以前的工作的基础上，我们调查了这两个Photorhabdus之间的竞争通过性状比较和共培养实验，可以研究区域（昆虫之间）和局部（昆虫内部）水平的物种。在支持线虫繁殖和保护尸体免受无脊椎动物清除剂方面，物种之间没有差异，但是灰葡萄孢在以下几个特征上胜过温霉：生长速度更快，更大的抗菌和抗真菌活性以及定居比例更高。共培养中的线虫 此外，在两个细菌共生菌都定居于单个线虫感染性幼虫的地方，灰葡萄假单胞菌往往在数量上占主导地位。之间的差异光杆状套件中的次级代谢产物的检测物种制备：P. temperata产生了几种不是由P.cinerea生产的化合物，包括蒽醌颜料。温度假单胞菌发出的生物发光也比灰质假单胞菌发光。生物发光和色素沉着可以保护尸体免受依赖视线的清除剂的侵害。我们得出的结论是，尽管灰葡萄球菌可能显示出更高的局部水平（在尸体内）竞争成功，但沙丘在空间异质环境中两种光合作用物种的共存受到尸体对不同地方重要防御的防御力的不同专长所青睐。威胁。