Suppressed localization of a major autolysin on Staphylococcus aureus treated with tetracycline

Surface localization of a major autolysin (atl gene product, ATL) on Staphy lococcus aureus treated with tetracycline (TC, 4MIC: 1.56 mug ml(-1)) was e xamined using the protein A-gold labelling method. No labelling was noted o n the surface of the next septal region, but it was observed on the previou s septal region. In contrast, on untreated cells the gold particles were fo und not only along the septal surface, but also on the next septal region. These findings agree with those obtained from both ultrathin and whole-moun t specimens, indicating that TC inhibits the localization of ATL in the nex t septal region. They further support the suggestion that ATL localization on the cell surface is closely associated with the cell cycle. When S. aure us was treated with other-wise lytic concentrations of penicillin G (PCG, 4 MIC: 0.02 mug ml(-1)) in the presence of TC, the distribution of the label on the cell surface was found to be very similar to that on the TC-treated organisms. This suggests that the inhibitory effect of TC on PCG-induced ly sis was not due to complete loss of ATL on the cell surface but instead to inhibition of ATL localization in the next septal region.