Query: NC_014228:4360676 Xenorhabdus nematophila ATCC 19061, complete genome
Lineage: Xenorhabdus nematophila; Xenorhabdus; Enterobacteriaceae; Enterobacteriales; Proteobacteria; Bacteria
General Information: This genus is a group of insect pathogens which live in a mutualistic relationship with the soil nematode family, Steinernematidae. Free-living, juvenile Steinernema spp. enter insect larvae through the digestive tract. They penetrate the larvae body cavity and release Xenorhabdus spp. into the hemolymph (blood). The bacteria multiply rapidly, killing the larvae, and providing suitable nutrient conditions for the growth and reproduction of the Steinernema spp. The nematode matures and reproduces. The new juveniles reassociate with Xenorhabdus spp. and are released into the soil. Unlike Xenorhabdus bovienii, which is found in different Steinernema spp., Xenorhabdus nematophila is associated specifically with Steinernema carpocapsae and can be used as a model for studying host specificity.
Subject: NC_005126:142500 Photorhabdus luminescens subsp. laumondii TTO1, complete genome
Lineage: Photorhabdus luminescens; Photorhabdus; Enterobacteriaceae; Enterobacteriales; Proteobacteria; Bacteria
General Information: This strain was isolated on Trinidad and Tobago. It is a symbiont of the nematode Heterorhabditis bacteriophora. Bioluminescent bacterium. This organism is unusual in that it is symbiotic within one insect, and pathogenic in another, the only organism that is known to exhibit this dual phenotype. Enzymes are then released by the bacteria that result in rapid degradation of the insect body, allowing both bacteria and nematode to feed and reproduce. During this period Photorhabdus luminescens releases bacteriocidal products, including antibiotics and bacteriocins, that prevent infection of the larva by competitive microbes. The result is promotion of Photorhabdus luminescens-nematode interactions that result in continuation of the symbiotic relationship. In order to engage in a symbiotic relationship with the nematode and a pathogenic one with the insect larva, the bacterium encodes specific factors that encourage both. These include a large number of genes that code for secreted toxins and enzymes, as well as genes that encode products for the production of antibiotics and bacteriocins. Secretion of these products occurs by an array of systems including type I, type II, and type III secretion systems. The type III system is closely related to the Yersinia plasmid-encoded type III system. Genes that promote symbiotic relationships are also encoded on genomic islands on the chromosome including some that affect nematode development. Virulence genes appear to be active during exponential growth. Symbiotic genes appear to function during stationary phase (post-exponential) growth. The switch from one state to another is controlled. Photorhabdus luminescens is capable of giving off light, a complex process that requires the products of the lux operon.