AME 18:227-233 (1999)  -  doi:10.3354/ame018227

ABSTRACT: 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 (>100 μm s^-1) found in marine bacterial communities and isolates. Monensin, carbonylcyanide-m-chlorophenylhydrozone (CCCP) and amiloride were used on Escherichia coli, Shewanella putrefaciens, Alteromonas 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 μM 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 μM CCCP and 20 μM 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 μM speed remained unchanged at about 20 μm s^-1 for marine bacterial communities. Sodium-ion 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.

KEY WORDS: Marine bacterial motors · Motility · Proton · Sodium-ion · Uncouplers