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Journal of Undergraduate Research

Keywords

mutant entemopathogenic bacterium, photorhabdus luminescence

College

Life Sciences

Department

Microbiology and Molecular Biology

Abstract

The bacterium Photorhabdus luminescence and the nematode Heterorhabditis bacteriophora share an intimate symbiotic relationship. Together, the pair preys on insect larva in the soil. Infective juvenile (IJ) nematodes seek out insect hosts by following chemical signals, such as CO2, given off by potential hosts. After locating the insect, IJs quickly invade the larva. In their new home, the nematodes regurgitate the bacteria they have been harboring in their gut. The bacteria immediately begin attacking the insect and then multiply within the fresh cadaver. The nematodes feed on the proliferating bacteria, sexually develop, and reproduce. In addition to acting as the food source for the nematode, the bacteria also produces a variety of microbicides to prevent secondary infections of the insect host. Once the host’s nutritional resources have been exhausted, IJs store colonies of bacteria in their gut and abandon their old host in search of new insect larva. In this way, the bacteria acts as the virulence factor of the entemopathogenic duo and the nematode acts as the vector, shuttling the bacteria to new larva. Without the bacteria, the nematode cannot kill. Without the nematode, the bacteria cannot spread to new hosts.

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