Wednesday, December 12, 2007 - 9:41 AM

Interactions between bacterial endosymbionts within a parasitoid host

Jennifer A. White,, Suzanne Kelly,, and Martha S. Hunter, University of Arizona, Entomology, 410 Forbes Building, PO Box 210036, Tucson, AZ

Bacterial endosymbionts are capable of manipulating their hostís reproduction for their own benefit. One such manipulation is cytoplasmic incompatability (CI), in which the sperm of infected male hosts is sabotaged to reduce production of female progeny by uninfected female mates, but can be rescued by infected female mates and used to produce infected female offspring. In this way, the proportion of infected females increases in the insect population, thereby promoting the propagation of the maternally-inherited bacteria. But what happens when more than one endosymbiont species inhabits the same host? The parasitoid wasp Encarsia inaron is naturally infected with two distantly related endosymbionts, Wolbachia and Cardinium, each of which can cause CI. We differentially cured E. inaron of each endosymbiont, and crossed hosts carrying different endosymbionts to determine 1) which bacteria cause the observed phenotype of CI in this parasitoid, and 2) whether the two bacterial species interact within their shared host. Preliminarily, it appears that both endosymbionts cause CI in E. inaron, but the effect is much stronger with Wolbachia than Cardinium. The mechanism of sperm sabotage appears to differ between the two bacteria, with the Wolbachia sperm modification dominating. Neither bacteria is able to rescue sperm modified by the other bacteria, but the presence of both Wolbachia and Cardinium within a female may interfere with the ability to rescue Cardinium-modified sperm. Finally, the Cardinium-induced CI is only evident in older wasps, suggesting that the bacterial community dynamics may shift over time, and that the bacteria may partition their host temporally.

Species 1: Hymenoptera Aphelinidae Encarsia inaron
Species 2: Hemiptera Aleyrodidae Bemisia tabaci (sweet potato whitefly)