Understanding the effects of indole on the induced acid stress response in Escherichia coli

Kaur, Manpreet (2023). Understanding the effects of indole on the induced acid stress response in Escherichia coli. University of Birmingham. Ph.D.

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Abstract

that the presence of signalling molecule indole at a concentration of 1 mM in the induction medium inhibits the activation of AR2 response in exponentially growing laboratory K-12 strains MG1655 and BW25113. This study shows that the inhibitory effect of indole on the induction of AR2 response in exponentially growing cells is also conserved in pathogenic strain O157:H7 Sakai. Furthermore, the AR2 response can also be highly and significantly induced through incubation at mildly acidic pH in early stationary phase O157:H7 Sakai, but not MG1655, BW25113 or commensal strain Nissle 1917. The induction of AR2 response in early stationary phase O157:H7 Sakai cells, however, cannot be blocked with indole. The regulation of AR2 response has been extensively studied, but mostly in K-12 strain MG1655. Whether these regulatory pathways are conserved in pathogenic and commensal strains is not known. In this study, the Transposon Directed Insertion-site Sequencing (TraDIS) was used to compare the genes of MG1655 and O157:H7 Sakai which are important for resistance to low pH. The frequency of inserts in several genes, which are known to be required for the optimal fitness of cells at low pH, reduced at pH 2.5 but not at pH 7, suggesting that TraDIS can be used to successfully study the effects of low pH and the inhibitory impact of indole on induced acid resistance in E. coli. Comparison between the acid stress responses of MG1655 and O157:H7 Sakai using GSEA suggested that same KEGG metabolic pathways determine the fitness of cells at low pH, although subtle differences are present between the responses of two strains. TraDIS results in MG1655 also showed an interesting connection between indole and the function of Fis. The mechanism behind the effect, however, remains to be elucidated.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):