Resistance ofEscherichia colito Penicillins IX. Genetics and Physiology of Class II Ampicillin-Resistant Mutants That Are Galactose Negative or Sensitive to Bacteriophage C21, or Both

Abstract

Ampicillin-resistant mutants of class II are determined by a doubling of chromosomally and episomally mediated ampicillin resistance on agar plates. Several mutants were isolated from a female as well as from an Hfr strain. The mutants differed from each other in various properties such as response to colicin E2 and sodium cholate, response to the phages T4 and C21, and fermentation of galactose. By conjugation and transduction experiments, it was shown that mutations in at least four loci gave the class II phenotype. The mutations were found to be in thegalUgene, thectrgene, and two new genes close tomtldenotedlpsAandlpsB. The carbohydrate compositions of the lipopolysaccharides of the mutants were investigated and found to be changed compared to the parent strains.GalUmutants lacked rhamnose and galactose and had 11% glucose compared to the parent strain. ThelpsAmutant also lacked rhamnose and had only traces of galactose and 58% glucose, whereas thelpsBmutant contained 14% rhamnose, traces of galactose, and 81% glucose compared to the parent strain.