Production by various Pseudomonas species of a factor modifying the enterobacterial common antigen.

The enterobacterial common antigen (ECA) is a common determinant shared by almost all members of the family Enterobacteriaceae. The antigen modifies erythrocytes for agglutination by ECA antibodies. Previously it was reported that Pseudomonas aeruginosa produces a factor (PF) which destroys the erythrocyte-modifying capacity of ECA. The present investigation was undertaken to determine whether other species of this genus also produce PF. The passive bacterial hemagglutination and hemagglutination inhibition tests were used. It was observed that 47 strains belonging to 8 species of the genus Pseudomonas produce this factor and 34 strains representing 12 other species do not. Multiple strains of a given species gave concordant results. Mucoid variants of P. aeruginosa produced more of this factor than did nonmucoid isolates recovered from the identical sputum specimens from patients with cystic fibrosis. ECA treated with PF no longer modifies erythrocytes for agglutination by ECA antibodies and exerts less antibody-neutralizing capacity than untreated antigen.

Type-specific antigens of group B type Ic streptococci.

The type-specific antigens of group B type Ic (old designation type Ii) streptococci were extracted, purified, and characterized by serological and chemical methods. The Ia antigen, shared by types Ia and Ic, is a polysaccharide composed of 69% galactose and 25% glucosamine (i.e., 31% N-acetyl-glucosamine). However, these monosaccharides failed to inhibit significantly the quantitative precipitin reactions between purified antigen and type Ia antiserum. Indications are that the immunodominant group of this antigen consists of more than a simple monosaccharide. The Ic antigen, shared by types Ib and Ic, is a protein unrelated to the X and R protein antigens. Ic antigen consists of two serologically active determinants, one of which is susceptible to both trypsin and pepsin digestion and the other to pepsin but not to trypsin digestion. Acrylamide gel electrophoresis of the partially purified Ic antigen resulted in the occurrence of both determinants throughout the length of the gel, as shown by double gel diffusion slides.

Inhibition of lipopolysaccharide O-antigen synthesis by colicin M.

Colicin M inhibits peptidoglycan biosynthesis at the level of the bactoprenyl carrier lipid. Since the synthesis of O-antigen also requires bactoprenyl carrier lipid, the effect of colicin M on O-antigen biosynthesis was studied using a colicin-sensitive strain of Salmonella typhimurium. Determination of O-antigen intermediates by two different methods showed that bactoprenyl-dependent O-antigen biosynthesis was inhibited by colicin M. Synthesis of both O-antigen and peptidoglycan was almost immediately inhibited following colicin addition. This was followed some 20 min later by cell lysis. The only known common step between O-antigen and peptidoglycan synthesis is formation of bactoprenyl phosphate by dephosphorylation of bactoprenyl pyrophosphate. Determination of bactoprenyl phosphates showed an accumulation of bactoprenyl pyrophosphate in colicin-treated cultures. It was concluded that dephosphorylation of the bactoprenyl lipid carrier was inhibited by colicin M, and this in turn prevented both O-antigen and peptidoglycan synthesis.