Fig 2. Minimum inhibitory concentration of benzalkonium chloride in WT and mutant L. monocytogenes strains.

A) Columns represent samples (WT, mut-1 and mut-2) and biological replicates, whole rows show the concentration (ug/ml) of benzalkonium chloride. Each component of the matrix shows the OD value after overnight growth. Growth was considered entirely inhibited when OD values < 0.1. The red shading represents OD value, with light and dark red representing low and high OD values. B) Minimum inhibitory concentrations of L. monocytogenes WT and mutants to benzalkonium chloride on solid media. 100 μl of overnight culture from the WT, mut-1 and mut-2 was spread onto TSA+YE plates with 0, 1, 2, 3, 4, 5, 6, and 7 μg/ml benzalkonium chloride and incubated at 37°C for 24 hours. Plates were then imaged on an Interscience Scan1200. Benzalkonium chloride minimum inhibitory concentration (MIC) was determined as the concentration at which no colonies were visible.