Exploration of gut bacteria in Frankliniella occidentalis (Pergande), Western Flower Thrips
Chanbusarakum L, Ullman D
University of California-Davis, Department of Entomology, One Shields Avenue, Davis, CA 95616.
Correspondence: ljchan@ucdavis.edu
Symbiotic bacteria often have a complex association with their host, be it human or arthropod. Many insects possess symbionts, though it is often difficult to determine the intricacies of their relationships. In one such case, facultative bacteria have been discovered in the hindgut of a major crop pest and virus vector, the Western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). The bacteria can be cultured outside thrips and are horizontally transmitted among WFT. Several thrips bacterial isolates have been studied in the Netherlands. Molecular data indicated thrips symbionts were similar to Escherichia coli, though biochemical properties suggested these microbes might actually be most similar to Erwinia. We focused on the bacterial flora of thrips originating from the Hawaiian Islands. Phenotypic data show that bacteria from thrips originating in the Hawaiian Islands and Netherlands were very similar. Molecular phylogeny based on the 16s rRNA gene suggested 2 separate groups of thrips bacteria were present in isolates from both geographic regions. One of the groups fell out closely with some Erwinia; however, bootstrap values for this classification were very low. Sound bootstrap values were not found for any of the relationships for the second group. The similarity between the microbes from different thrips in different locations and raised on different plant material suggest that the relationship between the bacteria and WFT are relatively stable and are not incidental infections arising from their environment.
