Measurements of the Ultraviolet Fluorescence Cross Sections and Spectra of Bacillus Anthracis Simulants

Abstract

Measurements of the ultraviolet autofluorescence spectra and absolute cross sections of the Bacillus anthracis (13a)simulants Bacillus globigii @g), Bacillus megaterium @m), Bacillus subtilis (Bs), and Bacillus cereus @c) were measured. Fluorescence spectra and cross sections of pine pollen (Pina echinata) were measured for comparison. Both dried vegetative cells and spores separated from the sporulated vegetative material were studied. The spectra were obtained by suspending a small number (< 10) of particles in air in our Single Particle Spectroscopy Apparatus (SPSA), illuminating the particles with light from a spectrally faltered arc lamp, and measuring the fluorescence spectra of the particles. The illumination was 280 nm (20 nm FWHM) and the fluorescence spectra was measured between 300 and 450 nm. The fluorescence cross section of vegetative Bg peaks at 320 nrn with a maximum cross section of 5 X 10"4 cm2/sr-nm-article while the Bg spore fluorescence peaks at310 nrn with peak fluorescence -1', 2 of 8 X 10 cm /sr-nrn-particle. Pine pollen particles showed a higher fluorescence peaking at 355 nm with a cross section of 1.7 X 10-'3cm2/sr-nm-particle. Integrated cross sections ranged from 3.0 X 10-'3for the Bg spores through 2.25 X 10-12(cm2/sr-particle) for the vegetative cells.

Modeling LIDAR Detection of Biological Aerosols to Determine Optimum Implementation Strategy

“…First, there are conflicting reports on the capability of being able to use wavelength-resolved fluorescence (or excitation-emission measurements) to identify different classes of biological agents, or even identify bacterial spores from vegetative bacteria. Some groups report differences (Shelly et al 1980a(Shelly et al , 1980bDalterio et al 1987;Bronk and Reinisch 1991;Sorrell et al 1994;Stephens 1998;Cheng et al 1999;Seaver et al 1999;Brosseau et al 2000;Wichert et al 2002;Agranovski et al 2003;Sivaprakasam et al 2004;Atkins et al 2007;Thomas and Airola 2007), and others don't (Seaver et al 1998;Cheng et al 1999). This issue needs to be resolved prior to proceeding with developing the instrumentation and data interpretation algorithms that will be needed to optimize multiple-wavelength UV fluorescence/IR LIDAR detection of biological warfare agent aerosols.…”

Fluorescence from atmospheric aerosol detected by a lidar indicates biogenic particles in the lowermost stratosphere

“…Also, the efficiency of such a process in the atmosphere depends on many parameters including temperature and pressure hampering an assessment of the possibility of detecting the fluorescence from these agents by our lidar. However, measurements of cross sections of the fluorescence of bacteria and pollen are available, a value of 5×10 −14 cm 2 nm −1 particle −1 for Bacillus globigii (Bg) and 2×10 −13 cm 2 nm −1 particle −1 for pine pollen when excited with light at 230 nm are reported by Stephens (1999). Given a scattering cross section in this order of magnitude, a concentration of fluorescing particles of about 0.1 cm −3 is calculated from the measured backscattered coefficient using Eq.…”

Fluorescence from atmospheric aerosol detected by a lidar indicates biogenic particles in the stratosphere

“…Also, the efficiency of such a process in the atmosphere depends on many parameters including temperature and pressure hampering an assessment of the possibility of detecting the fluorescence from these agents by our lidar. However, measurements of cross sections of the fluorescence of bacteria and pollen are available, a value of 5×10 −14 cm 2 nm −1 particle −1 for Bacillus globigii (Bg) and 2×10 −13 cm 2 nm −1 particle −1 for pine pollen when excited with light at 230 nm are reported by Stephens (1999). Given a scattering cross section in this order of magnitude, a concentration of fluorescing particles of about 0.1 cm −3 is needed to explain the measured signal.…”