: Symbiotic microbial relations are extremely pervasive, with examples being found among all levels of the earth's biota. These associations vary with regard to their interactive nature, and are characterized by the benefit (or detriment) imparted to the participants. Beneficial/neutral symbiotic associations are believed to have evolved from free living or parasitic ancestors. Closely related members of taxa can represent all trophic levels: from free-living to parasitic to mutualistic. Analysis of the genetic differences/similarities between these organisms, in reference to their symbiotic status, can provide important insight into the fundamental biological principles involved in shaping these particular relationships. Tsetse flies are the sole vectors of African trypanosomes, (Trypanosoma spp.), eukaryotic parasites that cause devastating diseases in humans and animals in Sub Saharan Africa. Since tsetse harbors three bacterial symbionts in addition to the protozoan trypanosomes, they provide an ideal model for studying symbiotic associations and interactions. Two of these bacterial symbionts (genus Wigglesworthia and genus Sodalis) are of particular research interest since they are closely related to important free-living and pathogenic bacteria of the Enterobacteriaceae. The genomes of Wigglesworthia, Sodalis and Trypanosoma spp. have been sequenced, which will facilitate in observing symbiosis at the genetic and functional level. Information on the interaction of tsetse symbionts with each other, with trypanosomes and with the host can be applied to other symbiotic systems (i.e., host-pathogen interactions). This study focuses on the genomic and functional biology of symbiosis in tsetse, in an attempt to understand how host factors/environment influence the architecture of microbial genomes during the evolutionary transition from free-living to symbiotic. This will be accomplished by examining functional biology of symbionts (by gene expression profiling) under different host nutritional states, developmental stages and varied parasite infection status. The role of functions typically associated with pathogenic microorganisms will be pursued in these beneficial microbes.
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