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United States Department of Agriculture

Agricultural Research Service

Research Project: MOLECULAR CHARACTERIZATION OF PATHOGENS AND THEIR RESPONSES TO ENVIRONMENTAL FACTORS

Location: Molecular Characterization of Foodborne Pathogens

Title: Ai-2 Quorum Sensing in Campylobacter Jejuni

Authors
item HE, YIPING
item CHEN, CHIN-YI

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 25, 2006
Publication Date: August 28, 2006
Citation: He, Y., Chen, C. 2006. Ai-2 quorum sensing in campylobacter jejuni. Meeting Abstract.

Technical Abstract: Quorum sensing response modulates many physiological attributes, such as bacterial virulence/pathogenesis, competence, and biofilm formation, when the bacterial population has reached a certain threshold. Among the various signaling compounds, autoinducer-2 (AI-2) is produced by most bacterial species, and is capable of cross-species signaling. Campylobacter species, a leading foodborne pathogen, was also shown to produce AI-2 –like compounds detectable by the Vibrio harveyi bioluminescence assay and carry the luxS gene encoding the enzyme involved in AI-2 synthesis. The production of AI-2 in C. jejuni strain 81-176 (a clinical isolate) is related to population density, with the maximal levels of AI-2 detected at the late log-phase to early stationary phase of bacterial growth (1 x 10^8 CFU/ml or higher). Levels of AI-2 in the culture supernatants decreased after 30 hours at 42-degree C, even though the cell concentrations remained constant. A luxS deletion mutant was constructed in C. jejuni strain 81-176 and the effects of AI-2 on bacterial growth and survival under various oxygen levels (5-21%) were studied. Our results showed that growth and survival of the luxS mutant were similar to that of the wild type under either microaerobic or aerobic conditions. Differences in gene expression between wild type and the luxS mutant were evaluated using microarrays. Our preliminary results showed that the mRNA levels of one gene, which encodes a conserved hypothetical protein with homologs only present in Helicobacter and Campylobacter species, were ca. 100-fold lower in the luxS mutant compared to that of the wild type. Further studies are needed to investigate the role of this gene/protein in the quorum sensing response of C. jejuni and apply this knowledge to develop potential intervention applications.

Last Modified: 7/28/2014
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