Cross-reactivity of major outer membrane proteins of Enterobacteriaceae, studied by crossed immunoelectrophoresis

Abstract

Outer membrane fractions were prepared from 11 bacteria in the family Enterobacteriaceae: Escherichia coli serotypes O1K-, O4K2, O26K60, O75K-, and O111K58, Shigella flexneri, Salmonella typhimurium, Klebsiella pneumoniae, Serratia marcescens, Protein vulgaris, Proteus mirabilis, and Providencia stuartii. All strains studied were found to contain one non-peptidoglycan-bound, heat-modifiable outer membrane protein, and one or two peptidoglycan-associated major outer membrane proteins in the 27,000- to 40,000-dalton range. Crossed immunoelectrophoresis using sodium dodecyl sulfate-polyacrylamide gel electrophoresis for separation of the antigens in the first dimension of the procedure was shown to provide a useful model system for studying the antigenic relationships of the major outer membrane proteins in Enterobacteriaeceae species. Peptidoglycan-bound major outer membrane proteins of all bacteria studied reacted with antiserum against the purified peptidoglycan-bound matrix protein I of E. coli O26K60 in this system. Non-peptidoglycan-associated proteins of all strains cross-reacted with protein II of E. coli O26K60 in both their unmodified and in their heat-modified forms. These results indicate that the genes coding for the major outer membrane proteins in the family Enterobacteriaceae have been well enough conserved during the course of evolution to allow significant antigenic crossreactivity between the corresponding proteins in different enterobacterial species.