Digitized Honors Theses (2002-2017)

Date of Award

5-2003

Document Type

Undergraduate Thesis

Degree Name

BS

Department

Biomedical Sciences

Faculty Mentor

Michael P. Spector

Abstract

Enteric bacteria, e.g. Salmonellae, must sense, respond to and survive many different stresses, e.g., carbon-energy (C)-source starvation. When an utilizable C-source becomes unavailable, Salmonella responds by inducing the starvation-stress response (SSR). The function of the SSR is to (1) protect the cell from the effects of long-term carbon-energy starvation and (2) provide a general resistance to other environmental stresses, e.g., extremes in pH, temperature, and exposures to antimicrobial peptides and H202. One SSR locus described is the narZfWV operon, which was shown to encode a nitrate reductase activity that is not regulated by either anaerobiosis or nitrate.

Originally, the enzyme was believed to be expressed at a low constitutive level, but recent data has indicated that narZYWV exhibits very complex regulation, involving sigma S for induction and cAMP:CRP, and other regulators, in repression . In addition another gene narU, encoding a nitrite extruder protein, is located directly upstream narZ. Reverse transcriptase-PCR (RT-PCR) amplifications using primers specific for narU only, or a region covering both the narU and narZ open reading frames indicate that: (1) narU is induced in 5-hour C-starved cells; (2) narU and narZYWV are co-transcribed in a polycistronic mRNA under the aforementioned conditions; and (3) the narU narZfWV

co-transcript appears to be induced during C-starvation. DNA sequence analysis of the upstream region of narU and the intergenic region between narU and narZ indicates putative sigma S and cAMP:CRP binding sites supporting previous results for narZ regulation.

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