Xenorhabdus
Encyclopedia
Xenorhabdus is a genus of bacteria that kills pests, and is released by the nematode Heterorhabditis bacteriophora
.
in the genus Steinernema and are pathogenic
towards a variety of insects. In the nematode, Xenorhabdus spp. are carried in a specialized region of the intestine
, termed the receptacle, of the third-stage infective juvenile (IJ). The IJs live in the soil until they invade the hemocoel of susceptible insect hosts. The bacteria are released in the insect hemocoel, where they overcome the insect's defense systems and produce numerous virulence factors that participate in suppressing insect immunity and killing the host. The bacteria proliferate to high levels in the insect cadaver and produce diverse antimicrobial compounds that suppress the growth of antagonistic microorganisms. Xenorhabdus spp. also secrete an array of exoenzymes that stimulate macromolecular degradation, the products of which, together with the bacteria themselves, are thought to provide a nutrient base for nematode
growth and reproduction. When nematode numbers become high and nutrients become limiting in the insect cadaver, nematode progeny re-associate with bacteria and differentiate into colonized, non-feeding IJs that emerge into the soil to forage for new hosts. Thus, the tripartite Xenorhabdus-nematode-insect interaction represents a model system in which both mutualistic and pathogenic
processes can be studied in a single bacterial species.
Heterorhabditis bacteriophora
Heterorhabditis bacteriophora also known as beneficial nematodes is a species of nematode worm that is used in gardening. They are useful to thwart ants, fleas, moths, beetles, flies, beetles, and other pests. They release Xenorhabdus bacteria from their digestive tract thus killing these pests....
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Lifecycle
Xenorhabdus spp. are motile, Gram-negative enterobacteria that form mutualistic associations with entomopathogenic soil nematodesEntomopathogenic nematode
Entomopathogenic nematodes are soil-inhabiting, lethal insect parasitoids that belong to the phylum Nematoda, commonly called roundworms. The term entomopathogenic comes from the Greek word entomon, meaning insect, and pathogenic, which means causing disease...
in the genus Steinernema and are pathogenic
Pathogenesis
The pathogenesis of a disease is the mechanism by which the disease is caused. The term can also be used to describe the origin and development of the disease and whether it is acute, chronic or recurrent...
towards a variety of insects. In the nematode, Xenorhabdus spp. are carried in a specialized region of the intestine
Intestine
In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...
, termed the receptacle, of the third-stage infective juvenile (IJ). The IJs live in the soil until they invade the hemocoel of susceptible insect hosts. The bacteria are released in the insect hemocoel, where they overcome the insect's defense systems and produce numerous virulence factors that participate in suppressing insect immunity and killing the host. The bacteria proliferate to high levels in the insect cadaver and produce diverse antimicrobial compounds that suppress the growth of antagonistic microorganisms. Xenorhabdus spp. also secrete an array of exoenzymes that stimulate macromolecular degradation, the products of which, together with the bacteria themselves, are thought to provide a nutrient base for nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
growth and reproduction. When nematode numbers become high and nutrients become limiting in the insect cadaver, nematode progeny re-associate with bacteria and differentiate into colonized, non-feeding IJs that emerge into the soil to forage for new hosts. Thus, the tripartite Xenorhabdus-nematode-insect interaction represents a model system in which both mutualistic and pathogenic
Pathogenesis
The pathogenesis of a disease is the mechanism by which the disease is caused. The term can also be used to describe the origin and development of the disease and whether it is acute, chronic or recurrent...
processes can be studied in a single bacterial species.