Multiwavelength transmission spectra of microorganisms and cell suspensions consist of combined absorption and scattering phenomena resulting from the interaction of light with microorganisms or cells typically suspended in a nonabsorbing media. The distribution of intensities as a function of wavelength depends on the size, shape, and optical properties of the sample. The optical properties are functions of the chemical composition and the state of aggregation, or association, of the chromophoric groups contained in the microorganisms. This article explores the growth behavior of Escherichia coli from the perspective of multiwavelength UV-Vis spectroscopy. Experimentally, it is demonstrated that the spectral signatures of the microorganism evolve as a function of time. It is also demonstrated that the spectral changes observed during growth are consistent with data reported elsewhere. From the theoretical point of view, it is demonstrated that the spectral signatures can be adequately represented with an interpretation model based on light-scattering theory. The parameters from the interpretation model reflect changes in size and chemical composition known to take place in the microorganisms during growth. (C) 2004 Wiley Periodicals, Inc.