Deletion of exoribonucleases impairs cell motility. Swimming ability was assessed on LB agar containing 0.25% agar. Strains were inoculated into the swimming media and incubated at 37°C. Pictures were taken regularly to monitor the increase of the swimming halo, here we are only showing the pictures taken after 23 h and 25 h of inoculation. The upper left corner of the plate was inoculated with wild-type cells and the bottom right corner was inoculated with either ∆rnb, ∆rnr or ∆pnp cells for better comparison between the wild-type and the different mutants.