Figure 2.

An example of Staphylococcus epidermidis response to bactericidal action of ciprofloxacin. (a) Top—Raman spectrum obtained for low antibiotic concentration (1 mg/L). The DNA peak at 785 cm⁻¹ is clearly visible together with phenylalanine peak at 1002 cm⁻¹, (b) Middle—mean value of ratio of maximum of Raman intensity at 785 cm⁻¹ versus 1002 cm⁻¹ for different concentration of applied ciprofloxacin measured from 10 different cells. Mean value of a control sample not exposed to antibiotic (red circle) is shown. (c) Bottom—Raman spectrum obtained for higher antibiotic concentration (4 mg/L). The DNA peak at 785 cm⁻¹ disappeared which indicates fragmentation of DNA. Note that the two peaks shown here (around 1130 cm^-1) could not be reliably determined from the analysis of the data.