Variability of Steady-State Bacterial Fluorescence with Respect to Growth Conditions

Abstract

The UV-excited (∼280 nm) fluorescence emission spectra from suspensions of several different species of bacteria are examined to determine to what extent differences in condition of growth change their spectra. This is an important factor if these spectra are considered for use for identification of species. It was found that the spectra were relatively invariant with respect to whether the bacteria were harvested during growth (log phase) or after the medium was depleted (stationary phase). For a given strain of Escherichia coli it was found that the emission spectrum did not change for growth in rich, compared to minimal, medium; however, there was some change for other species. For bacterial spores, the emission spectra were found to be similar for several species. An estimate was made for the quantum yield for Bacillus megaterium spores. The emission spectrum from spores and bacteria was found to change substantially on drying.