The PmrAB system in Erwinia amylovora renders the pathogen more susceptible to polymyxin B and more resistant to excess iron

The PmrAB system is a two-component regulatory system that responds to extracellular iron and acidic pH. The role of the PmrAB system in Erwinia amylovora remains unknown so far. Our results showed that the pmrAB mutants were more resistant to strong acidic conditions than the wild type (WT) strain. The survival rate of the pmrAB mutants was much higher than that of WT when treated with polymyxin B. However, pmrAB mutants were more sensitive to extracellular iron than WT strain. These results demonstrated that the PmrAB system in E. amylovora renders the pathogen more susceptible to polymyxin B and acidic pH, but more resistance to excess iron.