Production, purification, and characterization of the fimbrial adhesive antigen F41 isolated from calf enteropathogenic Escherichia coli strain B41M

Abstract

Enterotoxigenic Escherichia coli strains of serogroups O9 and O101 produce an adhesive antigen, provisionally designated as F41. Production of the F41 antigen was shown to be dependent on the composition of the growth medium. A minimal salts medium or Minca medium was the most suitable medium to obtain a high production. The biosynthesis of the F41 antigen was repressed at 18°C or in the presence of L-alanine. The F41 antigen was isolated from the bacteria by mechanical detachment, concentrated by precipitation with ammonium sulfate, and purified by gel filtration on Sepharose CL-4B and treatment with deoxycholate. The purified F41 was composed of protein subunits with an apparent molecular weight of 29,500 on sodium dodecyl sulfate-polyacrylamide gels. The isoelectric point of the antigen was 4.6. The N-terminal amino acid sequence was determined. The F41 antigen had strong hemagglutinating activity with guinea pig and human group A erythrocytes and weaker hemagglutinating activity with horse and sheep erythrocytes. In immunoelectrophoresis at pH 8.4 the purified antigen migrated to the anode. Purified F41 antigen has a filamentous structure with an average diameter of 3.2 nm.