Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 27, 2004
Publication Date: August 8, 2004
Citation: Chen, C., Irwin, P.L. 2004. The effect of Campylobacter jejuni population density on survival and AI-2 production at varying oxygen levels. International Association for Food Protection Program and Abstract Book. P132. pg. 95. Technical Abstract: The microaerophile Campylobacter jejuni is a significant food-borne pathogen, which carries the luxS gene responsible for a quorum sensing response involving autoinducer-2 (AI-2). Our results showed that C. jejuni strain 81-176 culture supernatants (conditioned media) elicit light in the Vibrio harveyi AI-2 bioluminescence assay. The minimal onset time to light induction, which is related to elevated AI-2 levels, was observed when C. jejuni population densities reached approximately 10^8 CFU/ml. A C. jejuni mutant containing a luxS deletion was constructed and culture supernatants from this mutant resulted in onset times similar to those of the media controls in the bioluminescence assays. Growth and survival under microaerobic and atmospheric oxygen conditions showed no differences between the wild type and luxS mutant. Both strains also survived longer under the aerated conditions at higher cell densities (10^7 to 10^8 CFU/ml) than at lower cell densities (10^6 CFU/ml or lower). Interestingly, conditioned media from either the wild type or luxS mutant prolonged the survival of Campylobacter in aerated cultures at lower cell densities (10^6 CFU/ml or lower) compared to that of fresh media. Such a protective effect was most pronounced in media harvested from 24-hour or older cultures and were not directly correlated with the levels of AI-2 production. This finding suggests that Campylobacter exudates may contain a non-AI-2 quorum sensing signal that is able to induce protective responses at higher oxygen levels. Alternatively, the exudates may contain secreted proteins that can provide direct beneficial effects related to survival in environments of elevated oxygen levels.