Transformation of Streptococcus sanguis to intrinsic penicillin resistance.
A series of step-level penicillin-resistant derivatives of Streptococcus sanguis V288 (Challis) were obtained through successive genetic transformations. The DNA donor used was a laboratory-derived, penicillin-resistant multistep mutant of the recipient strain. Detection of the penicillin-binding proteins (PBPs) of wild-type and transformants revealed five major PBPs. While it was found that S. sanguis can acquire intrinsic resistance in a stepwise manner and the mechanism was similar to those of some other organisms (changes in penicillin-binding protein affinity and/or in extent of penicillin binding), multiple-PBP changes accompanied a single step-level of resistance. All of the PBPs showed varying degrees of decreased affinity for [3H]benzylpenicillin with increasing penicillin resistance. Of these, the consistent, dramatic and progressive decrease of PBP 4 binding was most notable. After an initial decrease at the first step-level of resistance, PBP 5 was restored to wild-type levels, indicating a possible important role in survival. Genetic linkage of the first two step-levels of resistance was demonstrated by examination of transformation frequencies and by hit-kinetics experiments. A convenient method is described for the quantitative comparison of fluorographs containing PBPs with a wide range of affinities for penicillin.
Zito
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Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, PA 19140.
Daneo-Moore
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D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000032:analysis; D006602:Hexosyltransferases; D007700:Kinetics; D002267:Muramoylpentapeptide Carboxypeptidase / Q000032:analysis; D010403:Penicillin Resistance / Q000235:genetics*; D046915:Penicillin-Binding Proteins; D010406:Penicillins / Q000493:pharmacokinetics; D010458:Peptidyl Transferases; D013298:Streptococcus sanguis / Q000235:genetics*; D014170:Transformation, Genetic
D001426:Bacterial Proteins; D002352:Carrier Proteins; D046915:Penicillin-Binding Proteins; D010406:Penicillins; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase