Regulation of the mechanism of interference with Quorum sensing in Escherichia coli
Year: 2011
Type: dissertation
Abstract: Quorum sensing is a cell-to-cell signaling mechanism in which bacteria collectively control gene expression and therefore synchronize behaviors only productive at a high population density. The autoinducer-2 (AI-2) signal is produced by many bacteria and enables inter-species communication. In Escherichia coli, AI-2 is synthesized and secreted, accumulating in the extracellular medium. AI-2 concentration rises as bacteria divide and decreases rapidly in early stationary phase partially due to the expression of an ATP-binding cassette transporter, named Lsr (for LuxS-regulated) and encoded by the lsrACDB operon, which imports AI-2, removing it from the environment. Recent work showed that the phosphoenolpyruvate-dependent phosphotransferase system (PTS) plays an important role in the regulatory network of the Lsr transporter. Specifically, mutants in the ptsI gene, encoding for Enzyme I (EI) of the PTS, do not internalize extracellular AI-2 and do not activate the lsr operon. The present work showed that phosphorylation of EI is important for enabling the recovery of the defect of the ptsI mutation in AI-2 internalization but most likely not to phosphorylate AI-2 since LsrK kinase is required for AI-2 processing. In this study a genetic screen was performed to determine the molecular mechanism of the regulation of AI-2 internalization via EI by identifying suppressors of the ptsI mutant that can incorporate AI-2. A library of single-gene deletions of all non-essential genes in Escherichia coli in a ptsI deletion background strain carrying a lsr-lacZ promoter fusion was generated and screened for mutants with lsr-lacZ expression higher than the parent strain. Suppressors of the ptsI mutant were identified and the most interesting mutants are currently being analyzed to understand their role. The Lsr regulation was also studied using a new tool: green fluorescent protein (gfp) reporter fusions. These were compared with the commonly used promoter-lacZ fusions and their benefits and drawbacks were accessed. Understanding how the Lsr transport is dependent on the PTS, can reveal the molecular mechanism through which information about the physiological state of bacteria and regulation of AI-2 signal uptake is integrated.
Author: Paulo José Braz Correia Correia
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2285530557