Spectrally resolved absolute fluorescence cross sections for bacillus spores.

Area of Science:

• Microbiology
• Spectroscopy
• Biophysics

Background:

• Bacterial spores, including Bacillus subtilis and Bacillus cereus, are significant in various fields.
• Understanding their optical properties, like fluorescence, is crucial for detection and characterization.

Purpose of the Study:

• To quantify absolute fluorescence cross sections of bacterial spores.
• To determine optimal excitation wavelengths for spore fluorescence.
• To compare fluorescence between aqueous suspensions and aerosols.

Main Methods:

• Measured absolute fluorescence cross sections for Bacillus subtilis and Bacillus cereus spores.
• Utilized excitation wavelengths ranging from 228 to 303 nm.
• Spectrally resolved fluorescence at each excitation wavelength.
• Also measured Mie scattering and extinction cross sections for B. subtilis.

Main Results:

• Optimal excitation wavelength for spore fluorescence was identified between 270 and 280 nm.
• Fluorescence cross sections for aqueous suspensions were four times larger than for dry aerosols.
• Wet aerosols exhibited enhanced fluorescence compared to dry aerosols.

Conclusions:

• Bacterial spore fluorescence is significantly influenced by hydration state and physical form (suspension vs. aerosol).
• The findings provide valuable data for developing fluorescence-based detection methods for bacterial spores.