Project Title

The Effects of Dysregulating Cyclic-di-GMP Pathways on Survival of Salmonella in Chicken Eggs

Authors' Affiliations

Joseph Headrick, Department of Health Sciences, College of Public Health, East Tennessee State University, Johnson City, TN. Jacob Schultz, Department of Environmental Health, College of Public Health, East Tennessee State University, Johnson City, TN. Erez Mills, Department of Animal Sciences, The Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Jerusalem, Israel. Erik Petersen, Department of Health Sciences, College of Public Health, East Tennessee State University, Johnson City, TN.

Location

Culp Room 304

Start Date

4-6-2022 1:00 PM

End Date

4-6-2022 2:00 PM

Faculty Sponsor’s Department

Health Sciences

Name of Project's Faculty Sponsor

Erik Petersen

Additional Sponsors

Bert Lampson, Jennifer Hall

Classification of First Author

Graduate Student-Master’s

Competition Type

Competitive

Type

Oral Presentation

Project's Category

Microbiology

Abstract or Artist's Statement

In a world with growing resistance to existing antibiotics, new approaches to finding new antibacterials are essential to fighting infections. Concerningly, antibiotic resistance is a growing problem in commercialized farming, where contaminated chicken eggs contribute to causing an estimated 142,000 cases of Salmonella infections in the U.S. every year. Cyclic di-GMP (CDG) is a secondary messenger molecule that Salmonella uses to regulate many signaling pathways in response to the environment, including desiccation tolerance and biofilm production. Certain primary stimuli from the environment will cause Salmonella to make CDG, which will bind to an effector molecule to initiate a signaling pathway for a desired response. The ability to disrupt this pathway could showcase a new potential target for new therapeutics. I hypothesized that by dysregulating the CDG response in Salmonella Typhimurium, the survival of the bacterium on eggshells or in egg whites would be affected. Therefore, we investigated survival of S. Typhimurium in the presence of two known CDG modulators, L-arginine and salicylic acid, in the egg white and on the eggshell. L-arginine was previously found to activate production of CDG in S. Typhimurium, while salicylic acid was found to lower CDG levels. Bacteria were exposed to either L-arginine or salicylic acid (or plain media as a negative control) and tested for survival either within egg white or after two days of desiccation on an eggshell. Assessments were also made with bacterial strains that did not have proteins associated with the CDG pathway: BcsA, a CDG-responsive cellulose synthase that produces biofilm-forming exopolysaccharide and STM1987, the L-arginine-response diguanylate cyclase that generates CDG. In the presence of L-arginine, S. Typhimurium survival significantly increased within egg whites compared to wild-type, while salicylic acid exhibited no change in survival. Deletion mutants of BcsA or STM1987 showed similar results, implying that CDG-mediated cellulose synthesis may not be directly involved in L-arginine survival. This work is the foundation for further analysis of chemical inhibitors of S. Typhimurium in egg whites and on the surface of eggshells. We also plan to examine other naturally occurring compounds as well as do transposon analysis to further understand these signaling pathways and potentially present a new target for new antibiotics.

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Apr 6th, 1:00 PM Apr 6th, 2:00 PM

The Effects of Dysregulating Cyclic-di-GMP Pathways on Survival of Salmonella in Chicken Eggs

Culp Room 304

In a world with growing resistance to existing antibiotics, new approaches to finding new antibacterials are essential to fighting infections. Concerningly, antibiotic resistance is a growing problem in commercialized farming, where contaminated chicken eggs contribute to causing an estimated 142,000 cases of Salmonella infections in the U.S. every year. Cyclic di-GMP (CDG) is a secondary messenger molecule that Salmonella uses to regulate many signaling pathways in response to the environment, including desiccation tolerance and biofilm production. Certain primary stimuli from the environment will cause Salmonella to make CDG, which will bind to an effector molecule to initiate a signaling pathway for a desired response. The ability to disrupt this pathway could showcase a new potential target for new therapeutics. I hypothesized that by dysregulating the CDG response in Salmonella Typhimurium, the survival of the bacterium on eggshells or in egg whites would be affected. Therefore, we investigated survival of S. Typhimurium in the presence of two known CDG modulators, L-arginine and salicylic acid, in the egg white and on the eggshell. L-arginine was previously found to activate production of CDG in S. Typhimurium, while salicylic acid was found to lower CDG levels. Bacteria were exposed to either L-arginine or salicylic acid (or plain media as a negative control) and tested for survival either within egg white or after two days of desiccation on an eggshell. Assessments were also made with bacterial strains that did not have proteins associated with the CDG pathway: BcsA, a CDG-responsive cellulose synthase that produces biofilm-forming exopolysaccharide and STM1987, the L-arginine-response diguanylate cyclase that generates CDG. In the presence of L-arginine, S. Typhimurium survival significantly increased within egg whites compared to wild-type, while salicylic acid exhibited no change in survival. Deletion mutants of BcsA or STM1987 showed similar results, implying that CDG-mediated cellulose synthesis may not be directly involved in L-arginine survival. This work is the foundation for further analysis of chemical inhibitors of S. Typhimurium in egg whites and on the surface of eggshells. We also plan to examine other naturally occurring compounds as well as do transposon analysis to further understand these signaling pathways and potentially present a new target for new antibiotics.