Ion Selectivity of the Flagellar Motors Derived from the Alkaliphilic Bacillus and Paenibacillus Species.

Many bacteria can swim using their flagella, which are filamentous organelles that extend from the cell surface. The flagellar motor is energized by either a proton (H+ ) or sodium ion (Na+ ) as the motive force. MotAB-type stators use protons, whereas MotPS- and PomAB-type stators use Na+ as the coupling ions. Recently, alkaliphilic Bacillus alcalophilus was shown to use potassium ions (K+ ) and rubidium ions (Rb+ ) for flagellar rotation, and the flagellar motor from Paenibacillus sp. TCA-20 uses divalent cations such as magnesium ions (Mg2+ ), calcium ions (Ca2+ ), and strontium ions (Sr2+ ) for coupling. In this chapter, we focus on how to identify the coupling ions for flagellar rotation of alkaliphilic Bacillus and Paenibacillus species.