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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Insect Behavior and Biocontrol Research » Research » Publications at this Location » Publication #318058
Title: Identifying Francisella tularensis genes required for growth in host cells

Author
item BRUNTON, J - University Of North Carolina
item STEELE, S - Surry Community College
item MILLER, C - University Of North Carolina
item Lovullo, Eric
item TAFT-BENZ, S - University Of North Carolina
item KAWULA, T - University Of North Carolina

Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2015
Publication Date: 5/18/2015
Citation: Brunton, J., Steele, S., Miller, C., Lovullo, E.D., Taft-Benz, S., Kawula, T. 2015. Identifying Francisella tularensis genes required for growth in host cells. Infection and Immunity. DOI: 10.1128/IAI.00004-15.

Interpretive Summary: Tularemia is a bacterial disease caused by highly virulent Gram negative intracellular pathogen that is normally found in small animals, such as mice and rabbits, which can be passed to humans. Scientists at the USDA-ARS, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, in collaboration with University colleagues developed a mutagenic screen for the bacterium that had defective intracellular growth. One of the genes identified showed reduced viability and was associated with lowered membrane integrity. This gene product can serve as a new target for the development of novel antimicrobial compounds to control this disease.

Technical Abstract: Technical Abstract: Francisella tularensis is a highly virulent Gram negative intracellular pathogen capable of infecting a vast diversity of hosts, ranging from amoebae to humans. A hallmark of F. tularensis virulence is its ability to quickly grow to high densities within a diverse set of host cells including, but not limited to macrophages and epithelial cells. We developed a luminescence reporter system to facilitate a large scale transposon mutagenesis screen to identify genes required for growth in macrophage and epithelial cell lines. We screened 7500 individual mutants of which 269 exhibited reduced intracellular growth. Transposon insertions in the 269 growth defective strains mapped to 68 different genes. FTT_0924, a gene of unknown function but highly conserved among Francisella species was identified in this screen to be defective for intracellular growth within both macrophage and epithelial cell lines. FTT_0924 was required for full Schu S4 virulence in a murine pulmonary infection model. The FTT_0924 mutant bacterial membrane is permeable resulting in strongly reduced viability when grown in a hypotonic solution. The permeability and reduced viability was rescued when the mutant was grown in a hypertonic solution indicating that FTT_0924 is required for resisting osmotic stress. The FTT_0924 mutant was also significantly more sensitive to ß-lactam antibiotics than Schu S4. Taken together, the data strongly suggest that FTT_0924 is required for maintaining peptidoglycan integrity and virulence.