CELL ENVELOPE ALTERATIONS ASSOCIATED WITH SENSITIVITY TO ANTIBACTERIAL AGENTS OF GAMMA-IRRADIATION RESISTANT MUTANTS OF ESCHERICHIA COLI

Abstract

The principle underlying the sensitivity to antibacterial agents of wild type Escherichia coli P and its γ-irradiation resistant mutants was studied. These strains were classified as typical rough (R) strains, belonging to classes Ra (P and γ), and Rc (6γ and 12γ). The galactose-deficient (Rc) strains, 6γ and 12γ, leaked large amounts of alkaline phosphatase, acid phosphatase, 2, 3-cyclic phosphodiesterase, and β-galactosidase into the culture media during active growth, indicating defects in both the outer and inner membranes. Unlike strains P and γ, strains 6γ and 12γ were hypersensitive to Actinomycin-D, Bacitracin, Erythromycin, Kanamycin, Novobiocin, penicillin G, Rifamycin, Vancomycin, sodium deoxycholate (DOC), sodium dodecyl sulfate (SDS), ethylenediaminetetraacetic acid (EDTA), lysozyme, and Methylene Blue. Strains P, 6γ, and 12γ showed similar sensitivity to phages T2, T3, T4, T5, T6, and T7, and differed from strain γ, which was sensitive only to phages T2 and T4. Strains P and 6γ were sensitive to colicins E₁, E₂, E₃, G, H, and K, whereas strain γ was resistant to colicin H, and 12γ was tolerant to colicins H and K.
On the basis of these observations it is suggested that the leakage of periplasmic enzymes from and the sensitivity of these mutant strains to antibacterial agents are associated with both defects in the cell wall and plasma membrane.