%0 Journal Article %A Zito, Edward T. %A Daneo-Moore, Lolita %T Transformation of Streptococcus sanguis to Intrinsic Penicillin Resistance %D 1988 %J Microbiology, %V 134 %N 5 %P 1237-1249 %@ 1465-2080 %R https://doi.org/10.1099/00221287-134-5-1237 %I Microbiology Society, %X 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. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-134-5-1237