Significance of absorption spectra for the chemotaxonomic characterization of pigmented bacteria

A method for characterizing pigmented bacteria based on the numerical analysis of their carotenoid absorption spectra was examined. To achieve this, some non-phototrophic pigmented bacteria that were isolated from various environments and closely related types of species were used. Bacterial carotenoid pigments were extracted with an acetone:methanol (7:2) mixture and the absorption spectra were determined. Data were normalized, and their first derivatives were analyzed using Ward clustering algorithms. Based on the spectral data, isolates were separated into 7 groups. Characterization based on derivative pigment spectral data showed good agreement statistically with biochemical characterization results. The Mantel test indicated that the dissimilarity matrices of phenotypic tests and the pigment spectral data were correlated (P < 0.001). Absorption spectra can simplify and accelerate the identification and characterization of pigmented bacteria, when used with other distinctive biochemical tests. This method might be useful for determination of the microbial community structure in a variety of ecological studies.