Escherichia coli cultures grown on Tergitol-7 medium, with 2,3,5-triphenyltetrazolium chloride added, produced three main types of colonies: rough, intermediate, and mucoid. These colonies were yellow to amber in color and produced slight yellow zones in the medium. Rough colonies were flat, dry, and spreading, with a cut-glass appearance. Intermediate-type colonies varied considerably, but cou...