Spectral Fingerprints of Bacterial Strains by Laser-Induced Breakdown Spectroscopy

Abstract

Laser-induced breakdown spectroscopy (LIBS) is used to record the plasma emission for the colonies of vegetative cells or spores of five bacterial strains: Bacillus thuringiensis T34, Escherichia coli IHII/pHT315, Bacillus subtilis 168, Bacillus megaterium QM B1551, and Bacillus megaterium PV361. The major inorganic components of the bacterial samples, including Ca, Mn, K, Na, Fe, and phosphate, are clearly identified from the breakdown emission spectra. The bacterial spores accumulate a lot of calcium that shows strong LIBS emission at 393.7 and 396.9 nm. The diverse emissions from the phosphate component at 588.1 and 588.7 nm provide a fingerprint for bacterial strains. The relative change of inclusions in the bacteria is clearly distinguished by two-dimensional charts of the bacterial components. The results demonstrate the potential of the LIBS method for the rapid and low false-positive classification of bacteria with minimum sample preparation.