Bacteria size determination by elastic light scattering

Light extinction and angular scattering measurements were performed on three species of bacteria with different sizes and shapes ( Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis). The Gaussian ray approximation of anomalous diffraction theory was used to determine the average bacteria size from transmission measurements. A rescaled spectra combining multiple angular data was analyzed in the framework of the Rayleigh-Gans theory of light scattering. Particle shape and size distribution is then obtained from the rescale spectra. Particle characteristics (size and/or shape) retrieved from both methods are in good agreement with size and shape measured under scanning electron microscopy. These results demonstrate that light scattering may be able to detect and identify microbial contamination in the environment.