title: Investigation of the penicillinase activity in L colonies of Staphylococcus aureus.
abstract: Penicillinase-producing strains of Staphylococcus aureus are transformed into stable L colonies by 70 to 100 subcultures on methicillin-containing medium with a suitable high osmolarity. During transformation, the penicillinase activity is lost. This loss in activity is not the result of only the penicillinase-negative mutants transforming to L colonies. If unstable L colonies are filtered through 0.45-mum membrane filters immediately after transformation, still no penicillinase activity is seen; this is also the case if the filtrated L colonies are reverted into coccal forms. The mechanism responsible for the loss of penicillinase activity is discussed. A loss of the penicillinase plasmid is proposed as the most reasonable explanation.
mesh_terms: D001412:Bacillus subtilis; D001434:Bacteriophage Typing; D003470:Culture Media; D005374:Filtration; D005827:Genetics, Microbial; D007740:L Forms / Q000201:enzymology*; D008712:Methicillin; D009154:Mutation; D010405:Penicillinase / Q000032:analysis / Q000378:metabolism*; D013210:Staphylococcus / Q000201:enzymology* / Q000254:growth & development; D014170:Transformation, Genetic
chemical_list: D003470:Culture Media; D010405:Penicillinase; D008712:Methicillin