Comparative analysis of the protein composition of the external membrane of a virulent strain of Shigella sonnei and of genetically related avirulent bacteria

: The outer membrane proteins of intact S. sonnei cells of a strain virulent in the keratoconjunctival test contain up to 24 polypeptides; one of them (with a molecular weight of about 70 KD) is absent in similar preparations of avirulent nonpenetrating shigellae in phase I, genetically related to the above strain. Study of the composition of the outer membrane proteins of S. sonnei cells in phase II has revealed that these cells, when compared with smooth bacteria, show qualitative and quantitative differences in their polypeptide fractions; of these, three fractions are characteristic of rough bacteria.