title: Tolerance in Staphylococcus aureaus: evidence for bacteriophage role.
abstract: The conversion of nontolerant Staphylococcus aureus to a tolerant organism is reported. It had been shown previously that a nontolerant strain produces tolerant progeny when it is incubated in media that contain a bacteria-free filtrate derived from cultures of each of the three tolerant stains of S. aureus. The tolerant progeny retain the characteristic tolerance upon serial subculture, and cell-free filtrates prepared from such subcultures are capable of converting nontolerant organisms to tolerant bacteria. A study of filtrates made from one of the tolerant strains revealed that all of the converting activity was sedimented by ultracentrifugation. DNase I and RNase A did not reduce the activity of the sediment, but Proteinase K completely diminished it. Equilibrium centrifugation of filtrates in cesium chloride showed that the conversion activity was maximal in the fraction with a density of approximately 1.445 +/- 0.015 g/ml. When a portion of this fraction was examined with the electron microscope, hexagonal bacteriophages (20 nm in diameter) were seen at this density. This observation seems to be evidence that a bacteriophage is involved in conversion of S. aureus from a nontolerant to a tolerant organism.
mesh_terms: D007108:Immune Tolerance; D008242:Lysogeny; D008712:Methicillin / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance; D013204:Staphylococcus Phages / Q000276:immunology*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification
chemical_list: D008712:Methicillin