The Genetics of Penicillinase Production in Staphylococcus aureus Strain PS 80

Abstract

SUMMARYPS 80 is a naturally occurring, penicillinase-producing strain of Staphylococcus aureus, which differs from the majority of such strains in that the genetic determinants for penicillinase production are located on the chromosome. The strain is also resistant to various metal ions and the genes controlling these resistances are located on a plasmid-the n plasmid. When the strain is maintained on nutrient agar slopes at room temperature, a change occurs in its genetic constitution in that these unlinked genetic elements become closely linked and co-transducible with a high frequency. The results described in this paper are consistent with the hypothesis that the change is due to a duplication of the penicillinase genes with one copy of the genes being retained in its original chromosomal location and the other copy being incorporated in the 7~ plasmid.

Genetic Control In Methicillin-Resistant Strains Of Staphylococcus Aureus

“…With each of the lysates, an exponential decay in the transduction frequency with increasing exposure to UV light was observed. This is characteristic of most plasmid-borne genes (e.g., Arber, 1960;Asheshov, 1966Asheshov, ,1969. However, the initial transduction frequency from the lysate is much lower than that for most other plasmid genes (e.g., Asheshov, 1966; Dyke et al, 1970).…”

“…However, the strains had been stored for 30 mth before the transduction experiment was performed, and it is possible that during this time a piece of chromosome might have become extruded to form a plasmid, as has been described for the genes controlling penicillinase production (Asheshov, 1969). If this had occurred in the methicillin-resistant genes of strain no.…”

Transfer of Tetracycline-resistance between Strains of Staphylococcus aureus in Mixed Cultures

“…These curves are typical for plasmid-borne markers (e.g. Arber, 1960; Asheshov, 1966Asheshov, , 1969Poston, 1966). …”

An Unusual "Penicillinase Plasmid" In Staphylococcus Aureus; Evidence for its Transfer Under Natural Conditions

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E XTRACHROMOSOMAL elements that determine production of penicillinase can undergo experimentally a variety of changes within the staphylococcal cell : irreversible loss of the entire element (Novick, 1963) or loss of a fragment from the plasmid (Lacey and Grinsted, 1972), recombination between two of these plasmids (Richmond, 1969), reversible integration of part of the plasmid into the chromosome Richmond and Johnson, 1969), and acquisition of chromosomal genes (Asheshov, 1969). The occurrence of these events under natural conditions, with transfer of the plasmids between cells, could produce re-assortment of many of the available genes; this might occur despite the capacity of transduction to transfer only a small part of the cell genome at any one time.

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