3.4.6. ROS Defense

Mutations in bacterioferritin comigratory protein (BCP) were solely observed in planktonic populations 1 and 2 through selection. A single mutation in *bcp* was acquired on day 6 that persisted until day 27 in population 1, which aligned with a 128–512-fold increase in MIC from baseline. Two mutations in *bcp* were observed in population 2 on days 15–27 and day 36, consistent with 512–2048-fold increases in MIC from baseline (Table 3). BCP has roles in bacteria's defense against environmental ROS such as hydrogen peroxide [38]. It is likely that mutations in *bcp* are responses to oxidative stress posed by colistin treatment on bacterial cells.
