Fluorescence images of pre- and post-PUV-treated E. coli and L. monocytogenes cells in biofilms. The images represent cells in biofilms (48 h post-inoculation) receiving no PUV treatment (control), or PUV treatment for 20 s at a sample to light source distance of 8.8 cm (treated). The upper panels represent control cells of L. monocytogenes (a) and E. coli (b) recovered from lettuce. Lower panels depict the viability status of cells post-PUV treatment, L. monocytogenes (c) and E. coli (d) recovered from lettuce. Live or viable cells are represented by green fluorescence (AO+), while red fluorescence (PI+) indicates dead cells.