Identification of a sub-lethal HOCl concentration.

<p>Viability of <i>E</i>. <i>coli</i> MG1655 cells was analyzed in M9 minimal medium in the presence of the indicated concentrations of HOCl. Samples were removed after 10 min (A) or the indicated time points (B), serially diluted to 1:30, and spotted onto LB agar plates (1st to 5th dilution). (A) The viability was analyzed in 25 μM HOCl concentration steps. Cells were 100% viable at 0 and 25 μM HOCl. At 50 μM HOCl, they showed first indications of cell stress. Nevertheless, the cell viability remained at a high level. At 75 μM HOCl, the cells are harshly stressed and show a very low viability. (B) Cells were treated with 50 μM HOCl for various time points. The survival assay indicates cell stress; however, the viability remains high even after 60 min of HOCl treatment. The figure shown is the result of one representative experiment.