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Background: Since the discovery that Campylobacter (C.) jejuni produces Autoinducer 2 (AI-2), various studies have been conducted to explore the function and role of AI-2 in C. jejuni. However, the interpretation of these analyses has been complicated by differences in strain backgrounds, kind of mutation and culture conditions used. Furthermore, the research on AI-2 dependent phenotypes has to be conducted with AI-2 synthase (luxS) mutants as no AI-2 receptor has been found yet. But the mutation of luxS also leads to a disruption of the activated methyl cycle. Most studies lack sufficient complementation resulting in not knowing whether phenotypes of luxS mutants depend on disrupted metabolism or lack of AI-2. All this contributes to an intensive discussion about the exact role of AI-2 in C. jejuni.
Materials: We examined the impact of different media, temperature and chemically complementation on growth and motility of three different C. jejuni luxS mutants. Results: Our study showed that growth and motility of C. jejuni luxS mutants depend on strain background, mutation strategy and culture conditions. Complementation with AI-2 and AI-2+homocysteine significantly increased the cell number of C. jejuni NCTC 11168αluxS in stationary phase compared to the non-complemented C. jejuni NCTC 11168αluxS mutant. Also swarming ability could be partially complemented. With neither complementation, the phenotype of the wild type-strains was achieved, suggesting yet another reason for differing phenotypes other than communication and methionine metabolism for C. jejuni luxS mutants.
Conclusion: Further research should focus on the search for the AI-2 receptor to elucidate the exact role of AI-2 dependent behaviour in C. jejuni.