Uptake and extracellular depletion of AI-2 by S. oneidensis wild type. (A) Native cells of S. oneidensis washed in PBS depleted externally added AI-2 rapidly, while heat-killed cells were unable to do so. AI-2 was stable in PBS buffer. (B) AI-2 levels decreased in the non-treated as well as in the heat-inactivated supernatants. AI-2 was stable in LB medium.