The idea of selective inhibition of a synthesis essential to the parasite but inessential to the host as a basis for chemotherapeutic and antibiotic action has gained in sharpness of focus by virtue of contributions by P. D. Cooper1 of the Wright-Fleming Institute of Microbiology, by Lederberg,2 and by Park and Strominger.3
In 1949, Park and Johnson4 reported that uridine nucleotides accumulated in cultures of Micrococcus pyogenes var. aureus inhibited by penicillin. Subsequent work showed that similar compounds accumulated under penicillin inhibition of other gram-positive bacteria, and the data suggested that penicillin was preventing the incorporation into the bacteria of a principal product of bacterial synthesis. It now appears that the nucleotide contains two components, D-alanine and the amino sugar 3-0-carboxyethyl hexosamine, which have been found also in the cell walls of bacteria but not elsewhere in nature, as well as D-glutamic acid, an unusual natural