Figure 1

Levels of exogenous AI-2 decrease during culture with C.jejuni. Experiment A: In vitro produced AI-2 (10 μM final concentration) was added to LuxS01 mutant after 2.5 h growth in MHB (white bar). A control buffer of enzymatically synthesised SRH supplemented with homocysteine and adenine control culture but lacking AI-2 was added to LuxS01 as a control (undetectable AI-2, at baseline). For comparison production of AI-2 by the wild type NCTC 11168 strain (grey bars) and also a replicate culture to which the control buffer was added (black bars) is shown. At 0, 3 and 5.5. h after addition of in vitro synthesized AI-2, its activity was measured in the culture supernatant using the V. harveyi light assay. The supernatant activity is expressed as the fold increase in light production relative to sterile medium as a control. Experiment B: results for a similar experiment to that described in experiment A, except that the cultures were grown in MEM-α. As AI-2 was not produced by C. jejuni in this medium it was added to both the LuxS01 mutant (white bars) and the wild type strain NCTC 11168 (grey bars) after 2.5 h in culture. As controls the buffer mixture lacking AI-2 was added to LuxS01 mutant (undetectable AI-2 thus not indicated) and the wild type strain (black bars). To investigate the response of LuxS01 and wild type strain to exogenously added AI-2, cells from experiments A and B were harvested in late exponential phase for RNA extraction and microarray gene expression analysis. In both experiments the error bars represent 1 SD from the mean.