Interactions between the partners of the entomopathogenic bacterium nematode complexes, Steinernema-Xenorhabdus and Heterorhabditis-Photorhabdus

Abstract

Boemare et al., 1993) are Gram negative bacteria belonging to the family Enterobacteriaceae that have symbiotic and pathogenic relationshipswith invertebrates. The rst interaction is an intestinal association with soil dwelling nematodes of the family Rhabditidae, the Steinernema and the Heterorhabditis. The second is the action of these bacterial helminthic complexes towards insects. The former is symbiotic while the latter is pathogenic. Depending on the species, either one or both the symbiotic partners is entomopathogenic (Givaudan & Boemare, 2000). Sometimes it is only the combination of both that will kill insects (Akhurst & Boemare, 1990). More than 1000 microbial isolations have been conducted in the ve continents during the last 20 years, and all have reported these obligatory associations of Xenorhabdus with Steinernema and Photorhabdus with Heterorhabditis (Boemare et al., 1997; Forst et al., 1997). Gnotobiological experiments established accurately the symbiotic level of the association showing occurrence of speci c af nities that are not yet understood. In general terms, Photorhabdus strains are not accepted by Steinernema strains and Xenorhabdus strains are not accepted by Heterorhabditis. However, clinical strains of Photorhabdus, that are non symbiotic with nematodes and belong to the species P. asymbiotica (Fischer-Le Saux et al., 1999), have been reported from American immunocompromised patients (Farmer et al., 1989) or Australian people supposed to have been bitten by spiders (Peel et al., 1999).

Prospects for Using Entomopathogenic Nematodes to Control the Vine Mealybug, Planococcus ficus, in South African Vineyards

“…Heterorhabditids and steinernematids both have obligatory symbiotic associations with bacteria of the genera Photorhabdus and Xenorhabdus respectively (Boemare, 2001;Ehlers, 2001;Griffin et al, 2005). Both families have a life stage that is free-living and non-feeding, known as an infective juvenile (IJ), which is well adapted to long-term survival in the soil, where it seeks out an insect host (Ehlers, 2001).…”

An Overview of the Vine Mealybug (Planococcus ficus) in South African Vineyards and the Use of Entomopathogenic Nematodes as Potential Biocontrol Agent

“…In contrast, all Steinernematid generations are amphimictic (Griffin et al, 2005). Heterorhabditids and steinemematids have obligatory symbiotic associations with bacteria of the genera Photorhabdus and Xenorhabdus respectively (Boemare, 2001;Ehlers, 2001;Griffin et al, 2005). Photorhabdus and Xenorhabdus are both gram-negative bacteria belonging to the family Enterobacteriaceae (Boemare, 2001).…”

“…Heterorhabditids and steinemematids have obligatory symbiotic associations with bacteria of the genera Photorhabdus and Xenorhabdus respectively (Boemare, 2001;Ehlers, 2001;Griffin et al, 2005). Photorhabdus and Xenorhabdus are both gram-negative bacteria belonging to the family Enterobacteriaceae (Boemare, 2001). Steinernematid IJs retain Xenorhabdus symbionts within an intestinal vesicle, while Photorhabdus cells stick together in the anterior part of the Heterorhabditis gut (Boemare, 2001).…”

“…Photorhabdus and Xenorhabdus are both gram-negative bacteria belonging to the family Enterobacteriaceae (Boemare, 2001). Steinernematid IJs retain Xenorhabdus symbionts within an intestinal vesicle, while Photorhabdus cells stick together in the anterior part of the Heterorhabditis gut (Boemare, 2001).…”

“…The bacteria grow rapidly within the nutrient-rich haemolymph, while producing toxins and other metabolites that kill off the host within 24 to 48 hours after infection (Gaugler et al, 1997;Ehlers, 2001;Griffin et al, 2005). The bacteria also produce antimicrobial compounds that prevent the development of any other microbes within the cadaver, resulting in a monoxenic microcosm (Boemare, 2001). The nematodes then change into J3 juveniles, which feed on the symbiotic bacteria as well as on host tissue that is broken down by the bacteria.…”