Autofluorescence of live purple bacteria in the near infrared

Abstract

We have developed a novel microscope with which to study the fluorescence of cells in the near-infrared region (lambda = 750-2500 nm). For one of its first applications we report on the autofluorescence of live purple bacteria, Rhodospirillum rubrum, and suggest that the autofluorescent component is bacteriochlorophyll. The rapid fading of the autofluorescence of fixed bacteria and of purified bacteriochlorophyll suggests that the live bacteria are able to regenerate their pigment with a time constant of approximately 20 s.