AI-2 depletion by S. oneidensis wild type, WT control and luxS mutant. (A) S. oneidensis depleted AI-2 added at the beginning of growth (WT+AI-2, 0 h) at the end of the logarithmic phase like the control culture (WT). (B) When the wild type strain was supplemented with AI-2 after 10 h of growth (WT+AI-2, 10 h), as indicated by the dashed line, AI-2 activity increased strongly. Still, the wild type depleted AI-2 within one hour. AI-2 had a low decomposition rate under the tested conditions (stability control). (C) When the luxS mutant and the WT control were supplemented with AI-2 after 10 h of growth, both strains depleted AI-2 within one hour.