Investigation of blood fitness genes in the tsetse fly symbiont Sodalis glossinidius

Project summary/abstract: Tsetse flies (Genus: Glossina) are cyclic vectors of protozoan African trypanosomes (Trypanosoma sp.), the causative agents of human and animal African trypanosomiases, which impart a significant health and socioeconomic burden in sub-Saharan Africa. While only a small percentage of tsetse are infected with trypanosomes, they all house a

mixed population of indigenous endosymbiotic bacteria, including Sodalis glossinidius. S. glossinidius resides in tsetse’s midgut, which is exposed to large amounts of imbibed blood. The central hypothesis underlying the work proposed in this application is that S. glossinidius colonization of the tsetse gut requires expression of a suite of genes that enables the bacterium

to access nutrients from and survive within this blood-rich environment. The scientific goals of this project are to examine these hypotheses. In specific aim 1, S. glossinidius transposon libraries will be screened for candidate genes that contribute to fitness in blood. In specific aim 2, clean mutations in the candidate blood fitness genes will be generated and the mutants will

be characterized for in vitro growth and survival phenotypes in blood components. In specific aim 3, the S. glossinidius strains with null mutations in blood fitness genes will be tested for their ability to colonize the tsetse flies. Because a positive correlation exists between the density of S. glossinidius and the prevalence of trypanosome infection in tsetse’s midgut, a more complete

understanding of the Sodalis-tsetse symbiosis will have significant