Date of Publication


Document Type

Master's Thesis

Degree Name

Master of Science in Biology


College of Science



Thesis Adviser

Esperanza C. Cabrera

Defense Panel Member

Anton Lee
Cynthia T Hedreyda
Irene Samonte
Glenn G. Oyong


Salmonella enterica serovar Typhimurium remains the most frequently isolated in human salmonellosis, and can cause a systemic, typhoid-like disease in mice. The ability of enteric bacteria to survive and multiply in the human gastrointestinal environment is important for establishing infection. The process includes sensing changes in environmental conditions and responding with the appropriate gene regulation. One important adaptive strategy is the modification of the transcriptional apparatus in order to transcribe genes necessary to cope with a new condition and, to repress genes that are no longer needed. In this Study, the growth phase dependent expression of the yliH gene during the exponential and stationary phase was compared by DNA microarray analysis. The yliH gene was induced by up to 25 folds at the entry of stationary phase. The phenotypic expression of yliH induction at this stage was also confirmed by an increase in Beta-galactosidase activity of bacterial strains carrying yliH promoter-lac Z gene fusions inserted into the chromosome and in plasmid construct. The induction of yliH expression required positive regulation by the stringent signal molecule, alarmone guanosine-tetraphosphate (ppGpp). The physiological role of yliH in S. Typhimurium was determined by constructing a knock out mutant ( yliH) S. Typhimurium was constructed and its phenotype was compared with the wild type as to growth curve, invasiveness, biofilm architecture and cell adhesion. No remarkable difference in phenotypes was found among these parameters. This is the first experimental work to characterize the S. Typhimurium yliH gene and its regulation by the stringent signal molecule ppGpp. This work will support background for further study of this proteins unrevealed wide range of functions.

Abstract Format






Accession Number


Shelf Location

Archives, The Learning Commons, 12F Henry Sy Sr. Hall

Physical Description

56 leaves ; 28 cm.


Salmonella; Salmonella typhimurium

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