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