Hyperspectral Reflectance for Rapid Viability Assessment of Bacillus Endospores

A study was conducted to optically determine the viability of the Gram +, endospore-forming bacterial genera Bacillus using a hyperspectral reflectance spectrometer. Endospores are a dormant, differentiated cellular capsule form taken by select bacteria to ensure survival when environmental conditions become unfavorable. Two species of Bacillus were used for this study, Bacillus megaterium and Bacillus subtilis. These endospores were killed using a chemical treatment of sodium hypochlorite or a physical treatment of heat and pressure in an autoclave. The treated samples along with viable samples were lyophilized to form a powder. A reflectance spectrometer measuring 350 nm to 2500 nm (UV to shortwave infrared) was used to collect optical data on bulk powders. The resulting spectra were analyzed using several different methods, including integration and a Support Vector Machine (SVM) to obtain optimal separability of viable and nonviable endospores. Results of this study demonstrated the significant spectral separability of live and dead endospores with a level of confidence <0.05 in both species.