TisB is a small peptide encoded by the istR1/tisB type I toxin-antitoxin system in E. coli. Expression of tisB is under the control of the SOS response and is induced by DNA damaging treatments such as ofloxacin, a bactericidal antibiotic belonging to the fluoroquinolone class. We will describe the dormancy phenotype induced by TisB under ofloxacin treatment conditions and discuss how heterogeneous expression of tisB in a treated population affects survival.