An endosymbiont or endobiont is any organism that lives within the body or cells of another organism most often, though not always, in a mutualistic relationship. (The term endosymbiosis is from the Greek: ἔνδον endon "within", σύν syn "together" and βίωσις biosis "living".) Examples are nitrogen-fixing bacteria, which live in the root nodules of legumes, single-cell algae inside reef-building corals and bacterial endosymbionts that provide essential nutrients to insects.
Entomopathogenic nematodes (EPN) are a group of nematodes, that cause death to insects. The term entomopathogenic has a Greek origin, with entomon, meaning insect, and pathogenic, which means causing disease. They are animals that occupy a bio control middle ground between microbial pathogens and predator/parasitoids. Although many other parasitic thread worms cause diseases in living organisms, entomopathogenic nematodes are specific in only infecting insects. Entomopathogenic nematodes (EPNs) live parasitically inside the infected insect host, and so they are termed as endoparasitic. They infect many different types of insects living in the soil like the larval forms of moths, butterflies, flies and beetles as well as adult forms of beetles, grasshoppers and crickets. EPNs have been found all over the world in a range of ecologically diverse habitats. They are highly diverse, complex and specialized. The most commonly studied entomopathogenic nematodes are those that can be used in the biological control of harmful insects, the members of Steinernematidae and Heterorhabditidae. They are the only insect-parasitic nematodes possessing an optimal balance of biological control attributes.
Photorhabdus luminescens is a Gammaproteobacterium of the family Morganellaceae, and is a lethal pathogen of insects.
Heterorhabditis bacteriophora is a species of entomopathogenic nematode known commonly as beneficial nematodes. They are microscopic and are used in gardening as a form of biological pest control. They are used to control ants, fleas, moths, beetles, flies, weevils, and other pests.
Photorhabdus is a genus of bioluminescent, gram-negative bacilli which lives symbiotically within entomopathogenic nematodes, hence the name photo and rhabdus. Photorhabdus is known to be pathogenic to a wide range of insects and has been used as biopesticide in agriculture.
Photorhabdus temperata is a species of bacteria. It has been divided into 6 subspecies. It is pathogenic to certain insects.
Heterorhabditis megidis is a species of nematodes in the genus Heterorhabditis. All species of this genus are obligate parasites of insects, and some are used as biological control agents for the control of pest insects.
The xenortides (A-D) are a class of linear peptides isolated from the bacterium Xenorhabdus nematophila, a symbiont of the entomopathogenic nematode Steinernema carpocapsae. This class of compounds is known for their insect virulence and cytotoxic biological activities. The tryptamide containing compounds show higher biological activity than the phenylethylamides. The most biologically active compound was found to be xenortide B with a potency of less than 1.6 μM activity against Trypanosoma brucei rhodesiense and Plasmodium falciparum (malaria), however it is also the most toxic to mammalian cells which limits its viability as a treatment.
Xenorhabdus ehlersii is a bacterium from the genus of Xenorhabdus which has been isolated from the nematode Steinernema serratum in China.
Xenorhabdus bovienii is a bacterium from the genus of Xenorhabdus which has been isolated from the nematodes Steinernema bibionis, Steinernema krsussei, Steinernema affine, Steinernema carpocapsae, Steinernema feltiae, Steinernema intermedium, Steinernema jollieti and Steinernema weiseri. Xenorhabdus bovienii produces N-Butanoylpyrrothine, N-(3-Methylbutanoyl)pyrrothine and Xenocyloins.
Xenorhabdus griffiniae is a bacterium from the genus of Xenorhabdus which has been isolated from the nematode Steinernema hermaphroditum in Indonesia.
Xenorhabdus indica is a bacterium from the genus of Xenorhabdus which has been isolated from the nematodes Steinernema thermophilum and Steinernema yirgalemense. Xenorhabdus indica produces the Taxlllaids A–G.
Xenorhabdus khoisanae is a bacterium from the genus Xenorhabdus which has been isolated from the nematode Steinernema khoisanae in the Western Cape Province in South Africa.
Xenorhabdus szentirmaii is a bacterium from the genus Xenorhabdus which has been isolated from the nematode Steinernema rarum in Argentina. Xenorhabdus szentirmaii produces szentiamide, xenematide, bicornutin A xenofuranone A and xenofuranone B.
Xenorhabdus poinarii is a bacterium from the genus Xenorhabdus which has been isolated from the nematodes Steinernema glaseri and Steinernema cubanum.
Steinernema carpocapsae is an entomopathogenic nematode and a member of the family Steinernematidae. It is a parasitic roundworm that has evolved an insect-killing symbiosis with bacteria, and kills its hosts within a few days of infection. This parasite releases its bacterial symbiont along with a variety of proteins into the host after infection, and together the bacteria and nematode overcome host immunity and kill the host quickly. As a consequence, S. carpocapsae has been widely adapted for use as a biological control agent in agriculture and pest control. S. carpocapsae is considered a generalist parasite and has been effectively used to control a variety of insects including: Webworms, cutworms, armyworms, girdlers, some weevils, and wood-borers. This species is an example of an "ambush" forager, standing on its tail in an upright position near the soil surface and attaching to passing hosts, even capable of jumping. As an ambush forager, S. carpocapsae is thought to be especially effective when applied against highly mobile surface-adapted insects. S. carpocapsae can sense carbon dioxide production, making the spiracles a key portal of entry into its insect hosts. It is most effective at temperatures ranging from 22–28 °C (72–82 °F).
The Steinernematidae are a family of nematodes in the order Rhabditida.
Steinernema is a genus of nematodes in the family of Steinernematidae. The genus Steinernema is named after the nematologist Gotthold Steiner.
The Morganellaceae are a family of Gram-negative bacteria that include some important human pathogens formerly classified as Enterobacteriaceae. This family is a member of the order Enterobacterales in the class Gammaproteobacteria of the phylum Pseudomonadota. Genera in this family include the type genus Morganella, along with Arsenophonus, Cosenzaea, Moellerella, Photorhabdus, Proteus, Providencia and Xenorhabdus.
Necromeny is a symbiotic relationship where an animal infects a host and waits inside its body until its death, at which point it develops and completes its life-cycle on the cadaver, feeding on the decaying matter and the subsequent bacterial growth. As the necromenic animal benefits from the relationship while the host is unharmed, it is an example of commensalism.
