Date of Award

May 2014

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Biological Sciences

First Advisor

Gyaneshwar Prasad

Committee Members

Mark J. McBride, Daad Saffarini, Sergei Kuchin, Ching H. Yang

Keywords

Acid Inducible, Monoamine Compound, Salmonella, Sulfatase

Abstract

Salmonella enterica serovar Typhimurium is a gram-negative facultative intracellular food borne pathogen and accounts for $365 million in direct medical costs annually. The ability of S. Typhimurium to compete with the other microorganisms in the host gastrointestinal tract for nutrients and penetrate the epithelial mucosal layers is essential for its pathogenesis. The host mucosal glycans, the potential source of carbohydrates for gut microbiota, are heavily sulfated, making them resistant to digestion. The ability to produce sulfatases is important for utilizing the host-derived carbohydrates, intestinal adhesion, invasion of the host epithelium and systemic infection. The genomes of many enteric human pathogens contain annotated sulfatase genes, but very little is known about their regulation and physiological roles.

The genome of S. Typhimurium contains six annotated sulfatase genes. As a first step in elucidating the regulatory mechanisms of sulfatase expression, this study has characterized two of them: an acid-inducible sulfatase, encoded by STM0084 (aslA), and a monoamine compound induced sulfatase encoded by STM3122.

The acid-inducible aslA is regulated by the EnvZ-OmpR and PhoPQ two-component regulatory system and is likely secreted by the TAT secretion system. The aslA mutant was also found to be defective in intracellular survival. This study represents the first report of acid stress regulated sulfatases.

The STM3122-encoded sulfatase was monoamine compound induced (MCI) and regulated by a transcriptional regulator, encoded by STM3124. The MCI sulfatase was found to be modified by the enzyme encoded by STM3123 and was localized in the periplasm. Interestingly the sulfatase was co-expressed with the monoamine regulon comprising a transporter and an oxidoreductase. It appears that the MCI sulfatase might be important for utilization of monoamine compounds as a carbon source. Infection experiments with zebrafish showed that the STM3122 mutant was defective in intracellular colonization. These results suggest that sulfatases are involved in pathogenesis, and sulfatase inhibitors might serve as potential therapeutic targets against Salmonella infections.

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