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

This Project Grant award of $416,165 from the National Institute of Allergy and Infectious Diseases (CFDA 93.855 - Allergy and Infectious Diseases Research) supports research to investigate blood fitness genes in the tsetse fly symbiont Sodalis glossinidius. The central hypothesis is that S. glossinidius requires specific genes to access nutrients and survive within the blood-rich tsetse fly gut environment. The research goals are to screen S. glossinidius transposon libraries for candidate blood fitness genes, generate and characterize mutants of those genes, and test the ability of the mutant strains to colonize tsetse flies. This project has a period of performance from Sep 2024 to Aug 2027.

The grant includes a $32,454 sub-award to Yale University to introduce the mutant Sodalis strains into tsetse flies, perform biological assays, and assist with data analysis and manuscript preparation. The sub-award will also involve hosting undergraduate students from the University of Richmond to expose them to the tsetse fly research model.

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