Relation of R Factor and Chromosomal β-Lactamase with the Periplasmic Space

Abstract

The release of several R factor and chromosomal β-lactamases by osmotic shock treatment was studied. It was found that those β-lactamases with a molecular weight of about 20,000 were released, but those with a molecular weight of about 30,000 to 44,000 were not released during osmotic shock. This differential release did not depend on whether the structural genes were on the chromosome or on the genome of an R factor. The release or retention of the β-lactamases appeared to be a characteristic of the enzyme rather than the host cell since the same results were obtained when the R factors were harbored by a variety of host bacteria. Studies with bacteria which produced more than one β-lactamase showed that each enzyme reacted independently to the presence of other β-lactamases produced by the host bacterium.