Structural effects in quasi-elastic light scattering from motile bacteria of E. coli.

An extensive study has been made of the angular dependence of the intensity as well as the quasi-elastic intensity correlation function of light scattered from a dilute suspension of E. Coli K(12) bacteria in solution using the photon correlation technique. We have demonstrated that it is essential to consider the shape as well as the internal structure of bacteria in order to account fully for both the scattered intensity and the field self-correlation function as reduced from the intensity correlation function. The simple structure model previously proposed accounts well for both the intensity and diffusion data with a reasonable set of parameters. For the case of motile bacteria the observed field correlation function at small scattering angles is well represented by assuming a mixture of diffusive and straight line swimming motions of the bacteria. At larger scattering angles contributions of rotational motions become significant.