An extreme clockwise switch bias mutation in fliG of Salmonella typhimurium and its suppression by slow-motile mutations in motA and mot

The SJW2811 strain of Salmonella typhimurium is a switch-gene parenteral mutant strain that exhibits region II suppressor mutations involving motA and motB. The SJW2811 mutant strain exhibited strong clockwise motor bias with normal torque-generating mechanisms and lower swimming speed in liquid medium compared to wild type Salmonella typhimurium. The mechanism of suppression in the flagellar region II involved a small in-frame deletion in the middle of the fliG sequence which reduced motor function.