Single-particle levitation in conjunction with 264.3-nm laser excitation is used to measure the fluorescence emission of individual particles of <i>Bacillus globigii</i> spores. With precise humidity control, the fluorescence emission of wetted and desiccated <i>Bacillus</i> spore particles is measured from 300 to 450 nm. Comparison of spectra for <i>Bacillus</i> spores suspended in a standard buffer aqueous solution and for a desiccated 10-μm-diameter aggregate <i>Bacillus</i> spore particle shows that the spectra is virtually indistinguishable. However, at 85% relative humidity, corresponding to a 4.5M sodium chloride solution, the spore spectra redshifts by approximately 25 nm. It is postulated that the spectra redshifting is a result of specific interactions between the tyrosine fluorophore of the <i>Bacillus</i> spore and the phosphate moieties in the buffer solution.
© 1999 Optical Society of America
(140.7010) Lasers and laser optics : Laser trapping
(170.2520) Medical optics and biotechnology : Fluorescence microscopy
(170.6280) Medical optics and biotechnology : Spectroscopy, fluorescence and luminescence
Glenn O. Rubel and K. Hang Fung, "Influence of Saline Media on the Fluorescence Emission of Bacillus Spores," Appl. Opt. 38, 6673-6676 (1999)