Effect of mutation in phosphate specific transport (Pst) system on expression of adhesin genes in Enterohaemorrhagic Escherichia coli (EHEC)

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Effect of mutation in phosphate specific transport (Pst) system on expression of adhesin genes in Enterohaemorrhagic Escherichia coli (EHEC)

 

Author: Sze, Mei Kam
Title: Effect of mutation in phosphate specific transport (Pst) system on expression of adhesin genes in Enterohaemorrhagic Escherichia coli (EHEC)
Degree: M.Sc.
Year: 2013
Subject: Escherichia coli O157:H7 -- Genetic aspects
Phosphorus.
Biological transport.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Health Technology and Informatics
Pages: xviii, 114 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2637218
URI: http://theses.lib.polyu.edu.hk/handle/200/7058
Abstract: Introduction: Enterohaemorrhagic E. coli (EHEC) is a zoonotic pathogen associated with human intestinal diseases ranging from bloody diarrhea to hemolytic uremic syndrome (HUS). Adhesion is a critical early step of bacterial colonization of the intestinal mucosa and is one of the virulence factors to achieve EHEC infection. The expression of virulence factors has a linkage with the genetics of phosphate specific transport (Pst) system, which belongs to pho regulon. pho regulon is important in phosphate homeostasis. Mutations of pst genes may impose an impact on pho regulon and create a problematic bacterial sensation of the environmental inorganic phosphate level that may alter the virulence traits such as adhesion factors. Moreover, an environment change in phosphate concentration may affect the bacterial virulence such as adhesion to fruits and vegetables. Phosphate may be used to in animal husbandry and agriculture to work against the adhesion of EHEC that may function as a therapeutic agent to facilitate the elimination of EHEC. Aims: The aims of this study were to investigate the effect of pstC gene mutation in Pst system on the expression of adhesin genes in EHEC such as O157:H7 and O15. Methods: EHEC strains were cultured for RNA extraction and purification. Expression of adhesin genes were detected by real-time RT-PCR. The variations of adhesin genes expression levels were determined via 2-ΔΔCT method of relative quantification. Results: For EHEC O157:H7, there was less than two-fold change both in toxB and csgA expression (toxB, 1.97 folds, p=0.04; csgA, 1.63 folds, p=0.01) of the wild type grown under 10 mM inorganic phosphate condition relative to normal phosphate condition. When the pstC mutant mut 2 was compared against the wild type, there was more than two-fold change (2.36 folds, p=0.04) in ompA expression grown under 10 mM inorganic phosphate condition. For EHEC O15, there was more than seven-fold change in csgA expression of the wild type (7.2 folds, p=0.02) and pstC mutant strain (-10.03 folds, p=0.04) grown under 10 mM inorganic phosphate condition relative to normal phosphate condition. When the wild type was compared against pstC mutant strain, there was more than 26-fold change (-26.34 folds, p=0.03) in csgA expression grown under 10 mM inorganic phosphate condition. Conclusion: Transcription profiles observed between the six adhesin genes varied greatly in the wild type EHEC and in pstC mutants under different inorganic phosphate concentrations. Each adhesin genes have unique mechanism acting on their gene expressions. Mutation in pstC showed heterogenous expression patterns of adhesin genes in EHEC.

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