"The fiagella remain active during a twiddle ; the angular deviation is much larger
than can be accounted for on the basis of diffusion. When a bacterium swims up
a spatial gradient of an attractant (L-aspartate, L-serine), the probability per unit
time that a twiddle will occur is smaller than it is in an isotropic solution; when it
swims down the gradient, the probability is the same as it is in an isotropic
solution. Other parame ..."