THE RHODOBACTER-SPHAEROIDES FLAGELLAR MOTOR IS A VARIABLE-SPEED ROTOR

The rotation rate of the unidirectional stop/start motor of Rhodobacte r sphaeroides was investigated using computerised motion analysis of t ethered cells. The R. sphaeroides motor was found to have a variable r otation rate compared to the virtually constant-speed motor of wild-ty pe and CheR mutant (smooth swimming) Escherichia coli. In addition, th e dynamics of the R. sphaeroides motor during stopping was analysed wi th no consistent correlation behaviour, The motor could go from full r otation to stop, or stop to full rotation within one video frame, i.e. 0.02 s, but it could also slow down into a stop or restart slowly, ta king up to 0.25 s, The R. sphaeroides motor under chemokinetic stimula tion was also analysed and was found to show increased torque generati on and reduced variation in rotation rate. (C) 1997 Federation of Euro pean Biochemical Societies.