| Laser-Induced Breakdown Spectroscopy (LIBS) has many applications in medicine, industry and even the military. This research focuses on using LIBS to differentiate between different strains of the same bacterial species and between species of two similar bacteria. LIBS works by using a pulsed laser to ablate a sample material. During ablation a plasma is created which emits light from the excited atoms. The light is collected using a spectrometer and recorded. This information is then analyzed to determine the atomic composition of the sample.;I have identified 19 emission lines arising from six elements present in the bacteria in the LIBS spectra from Gram-negative bacteria. Using this information and a data analysis technique called Discriminant Function Analysis, I have shown for the first time that LIBS provides a fast, accurate method to differentiate between multiple strains of E. coli, including, most importantly, the pathogenic strain EHEC (E. coli O157:H7) responsible for illness and death in humans. In addition, I describe the investigation of the ability to discriminate E. coli from the pathogenic bacterium Pseudomonas aeruginosa. I also describe the effect that culturing the bacteria on various growth media has on this discrimination.;Lastly, I suggest several ways in which these results could be made more reproducible, more sensitive, and more applicable to a wider range of bacteria in future applications. |
