Grouping of streptococcus mitis strains grown on different growth media by FT-IR

Grouping of nine Streptococcus mitis strains grown on two different growth media was made by Fourier transform infrared spectroscopy. The IR spectra of the S. mitis strains grown on blood agar plates were broadly similar with amide I and amide II absorption bands at 1653 and 1541 cm −1 respectively, phosphate bands at 1237 cm −1 and sugar bands at 1070 cm −1 next to hydrocarbon absorption bands in the wavelength region between 3000-2800 cm −1. Seven out of nine tested S. mitis strains grown on TY agar showed an additional absorption band in the 3000-2800 cm −1 wavelength region indicative for the presence of an amphiphilic molecule and absent when the organisms were grown on blood agar.