Figure 1. Effect of PGPE on C. violaceum.

‘Control’ in this figure is the vehicle control (0.5%v/v DMSO), which did not exert any effect on growth and violacein production of C. violaceum. ( A) Effect of PGPE on growth and QS- regulated violacein production in C. violaceum: Bacterial growth was measured as OD ₇₆₄; OD of violacein was measured at 585 nm, and Violacein Unit was calculated as the ratio OD ₅₈₅/OD ₇₆₄ (an indication of violacein production per unit of growth); Catechin (50 µg/ml) did not exert any effect on growth of C. violaceum, but inhibited violacein production by 47.69±0.03%. ( B) PGPE acts as a signal-response inhibitor against C. violaceum. ( C) PGPE-pre-treatment enhances susceptibility of C. violaceum to different antibiotics. ( D) PGPE-treatment attenuates virulence of C. violaceum towards C. elegans: Catechin (50 μg/ml) and ampicillin (500 μg/ml) employed as positive controls conferred 100% protection on worm population, and pre-treatment of bacteria with PGPE at concentrations (10, 25, 50 and 100 μg/ml) other than those shown in figure allowed 75%, 77.5%, 80%, and 75% worm survival, respectively; DMSO present in the ‘vehicle control’ at 0.5%v/v did not affect virulence of the bacterium towards C. elegans; DMSO (0.5%v/v) and PGPE at tested concentrations showed no toxicity towards the worm. * p<0.05, ** p<0.01, *** p<0.001; AS, antibiotic susceptibility; QS, quorum sensing; PGPE, Punica granatum peel extract.