Influence of cultural conditions and mutations on the composition of the outer membrane proteins of Escherichia coli.

Various Escherichia coli strains differ in the composition of their major outer membrane proteins. However, all E. coli K12 strains tested possess the same major outer membrane proteins a, b, c and d, although quantitative differences were detected. The influence of growth conditions on the composition of the major outer membrane proteins of E. coli was analyzed. It was found that neither the growth phase at which the cells are harvested, nor the fatty acid composition of the phospholipids has a considerable influence on the composition of these proteins. However, the composition of the growth medium, and, to a less extent, the growth temperature, have a pronounced influence. Certain mutants, changed in the composition of their lipopolysaccharide, are deficient in protein b. Also mutants deficient in protein c and d respectively, are described. Proteins b and c of E. coli K12 were found to be associated with peptidoglycan. Protein bands, corresponding with flagellin and pilin respectively, were identified.