title: A plasmid-linked caseinolytic activity in Enterobacteriaceae.
abstract: We have tested for production of caseinolytic activity the strain of E. coli K12 J62 carrying different R factors from various Enterobacteriaceae of clinical isolates. The results obtained showed the presence of a caseinolytic activity in 7 out of 139 R factors tested. All of these positive (cas+) R factors derived from strains of Klebsiella pneumoniae and all were able to transfer a strong lac+ phenotype as well as multiple antibiotic resistances (R-lac factors). Another strain of E. coli K12, J53, which is plasmid-free, produced levels of caseinolytic activity comparable to those of the Klebsiella R factors; J62, on the contrary, appeared to possess an inhibitor specific for the caseinolytic activities of J53 and of the R factors but not of other cas+ Gram+ and Gram- organisms. The hypothesis that the expression of the cas+ phenotype in E. coli K12 may be due to the presence of plasmid-linked regulatory genes is discussed.
mesh_terms: D002364:Caseins / Q000378:metabolism; D004755:Enterobacteriaceae / Q000201:enzymology* / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology; D005798:Genes, Bacterial; D005809:Genes, Regulator; D008040:Genetic Linkage; D007711:Klebsiella pneumoniae / Q000201:enzymology; D010447:Peptide Hydrolases / Q000235:genetics*; D011815:R Factors
chemical_list: D002364:Caseins; D010447:Peptide Hydrolases