Angular Dependence of Scattering from Escherichia coli Cells

Abstract

The scattering of visible light from randomly oriented systems of heterogeneous E. coli cells in water was measured as a function of angle for 10–90°. The cells are assumed to be prolate ellipsoids of revolution whose dimensions are independently measured. For these cultures the average cell volume and axial ratio is 0.6 μ³ and 2.81, respectively. Using the measured dimensions, the Rayleigh-Debye approximation for the homogeneous ellipsoid was used to calculate theoretical scattering. A newly developed Rayleigh-Debye equation for a coated ellipsoid was also used. Both cell models lead to good theory–experiment agreement, especially the coated ellipsoid model. The absolute position of the two observed scattering minima and the wavelength dependence of these positions is in excellent agreement with the theoretical predictions. The existence of the scattering minima in randomly oriented heterogeneous cultures of E. coli is attributed to the uniformity of their minor axes.