Observed frequency-independent torque in flagellar bacterial motors optimizes space exploration.
A surprising feature of many bacterial motors is the apparently conserved form of their torque-frequency relation. Experiments indicate that the torque provided by the bacterial rotary motor is approximately constant over a large range of angular speeds. This is observed in both monotrichous and peritrichous bacteria, independently of whether they are propelled by a proton flux or by a Na(+) ion flux. If the relation between angular speed ω and swimming speed is linear, a ω-independent torque implies that the power spent in active motion is proportional to the instantaneous bacterial speed. Using realistic values of the relevant parameters, we show that a constant torque maximizes the volume of the region explored by a bacterium in a resource-depleted medium. Given that nutrients in the ocean are often concentrated in separate, ephemeral patches, we propose that the observed constancy of the torque may be a trait evolved to maximize bacterial survival in the ocean.
IFEG-CONICET and FaMAF, Universidad Nacional de Córdoba, 5000 Córdoba, Argentina.
Mario E
ME
Di Salvo
C A
CA
Condat
D000465:Algorithms; D001419:Bacteria / Q000166:cytology*; D018407:Bacterial Physiological Phenomena; D001703:Biophysics / Q000379:methods*; D005407:Flagella / Q000378:metabolism*; D007477:Ions; D008954:Models, Biological; D015233:Models, Statistical; D009792:Oceans and Seas; D012964:Sodium / Q000737:chemistry; D019415:Torque; D014783:Viscosity; D014871:Water Microbiology
D007477:Ions; D012964:Sodium