[Fluorescent probe study of staphylococcal cell wall charges]

The effect of pH and MgCl2 concentration on the fluorescence of 1-anilinonaphthalene-8-sulfonate (ANS), an anion probe, was studied in suspensions of Staphylococcus aureus. The maximum of ANS fluorescence shifted towards the short wavelength region of the spectrum and its intensity increased when the cells were incubated in the medium with low pH and high ionic strength. The results are discussed in terms of electrostatic interactions between the anions of the probe and the negative space charge of the cell wall.