Mechanisms of resistance in Escherichia coli to the sideromycin antibiotic no. 216: isolation and characterization of the resistant mutants

Abstract

Escherichia coli easily developed resistance to a new antimicrobial agent of the sideromycin group, No. 216, by spontaneous mutation. Most of the No. 216-resistant mutants tested proved not to be cross-resistant to E. coli phages T1, T5, and ø80. On the other hand, these phage-resistant mutants were cross resistant to No. 216. The initial site for binding of No. 216 to the sensitive cells was located, at the ton A gene product (Ton A-protein) of the outer membrane. However, unlike the phage-resistant mutants, ton A protein (78K-protein) in most No. 216-resistant mutants was intact and these mutants were possessed a particular 87K protein in the outer membrane. It is suggested that No. 216 is taken up by ton A protein and then penetrates into the cell by way of a particular transport system and that a highly mutable portion may exist in this reaction system.