Insect Virulence Mechanisms against Entomopathogenic Nematodes: Understanding the Molecular Basis of Host-Parasite Interactions

Abstract

Nematodes have demonstrated remarkable adaptability, occupying an extensive array of ecological niches, particularly as parasites. Among these parasitic nematodes are the entomopathogenic nematodes, which have formed associations with insect pathogenic bacteria, often lethal to their insect hosts. Notably, two nematode genera, Heterorhabditis, and Steinernema, have evolved to coexist with specific bacteria, Photorhabdus, and Xenorhabdus, respectively. This symbiotic partnership equips them with the ability to kill insects and utilise them as a source of sustenance. A critical phase in this process involves specialized infective stage IJ3, non-feeding juveniles. These IJ3 nematodes are adept at locating and invading suitable insect hosts, often through natural openings like anus, mouth, and spiracles. These hosts typically carry symbiotic bacteria within their intestines. Upon invasion, the nematodes release the bacteria into the insect host. This co-infection has multifaceted effects, including the suppression of host insect’s immune system and induction of septicemia. This ultimately leads to the host’s demise within a short timeframe of 24 to 48 hours. Once the insect host has perished, the nematodes, aided by the bacteria, contribute to the decomposition of the cadaver, thus accessing essential nutrients. They also serve as guardians, preventing opportunistic bacteria and fungi from utilising the nutrient-rich cadaver. After exhausting the available resources within the insect host, the entomopathogenic nematodes transition into colonised infective stages, ready to embark on their quest for a new insect host. This unique relationship between nematodes and bacteria is mutualistic in nature. Nematodes act as vectors, transporting the bacteria into the host, where they thrive and create optimal conditions for the nematodes’ survival and reproduction within insect cadavers. This intricate mechanism of insect infection through nematodes has found applications in pest management practices, making it an integral component of Integrated Pest Management (IPM) programs. © 2024 by Nova Science Publishers, Inc. All rights reserved.