Induction of capsular exopolysaccharide by translation-inhibitor antibiotics is non-mutational.

<p><b>A</b>. Sub-MIC Cm treatment does not select for mutants that constitutively hyperproduce exopolysaccharide. 4 independent lineages of WT bacteria not previously exposed to antibiotics were grown overnight with Cm10 (day 2) followed by restreaking in the absence of antibiotics (days 3–4). Colonies on day 4 were reinoculated into LB with or without Cm10. Capsular exopolysaccharide in cell-free supernatants was analyzed with alcian blue. <b>B</b>. Sub-MIC Cm pretreatment increases phenotypic resistance to Cm independent of the K locus. Cell populations from d2 were analyzed for CFE on Cm plates. Data are presented as in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004691#ppat.1004691.g003" target="_blank">Fig. 3</a>. Colonies arising from Cm10-pretreated WT cells plated on the indicated Cm concentration (arrowheads) were tested for mutational high-level Cm^R by passaging twice on LB agar without antibiotics, then scoring for increased growth on 100 μg/ml Cm. Fractions above the arrowheads denote the ratio of clones demonstrating increased growth on Cm compared to the WT grown in absence of Cm.