High speed marine bacteria use sodium-ion and proton driven motors

The ocean's strong ionic environment may be important for motility in marine bacteria. This is because flagellar motors are powered by dissipation of ion gradients across their cell membranes. We tested how much the 2 known motor systems contributed to the high speed motility (> l00 pm SS') found in marine bacterial communities and isolates. Monensin, carbonylcyanide-mchlorophenylhydrozone (CCCP) and amiloride were used on Escherichia coli, ShewaneUa putrefaciens, Alterornonas haloplanktis, a marine isolate (BBAT1) and marine bacterial communities to uncouple sodium-ion and proton gradients from motility. E. coli motility was stopped by 10 pM CCCP. Use of any of the 3 uncouplers alone slowed, but did not stop, S. putrefaciens, A. haloplanktis and a community of marine bacteria. A combination of 20 phl CCCP and 20 p M monensin stopped S. putrefaciens and A. haloplanktis. The same concentration combination reduced marine community speeds by half, but stopped few cells. Above uncoupler concentrations of 30 pM speed remained unchanged at about 20 pnl S-' for marine bacterial communities. Sodiumon motors were responsible for about 60% of marine bacterial speed. From the results it was concluded that most high speed marine bacterial community members used sodium and proton motors simultaneously.