CHARACTERIZATION OF A TYPE-IV BUNDLE-FORMING PILUS (SFP) FROM A GASTROENTERITIS-ASSOCIATED STRAIN OF AEROMONAS-VERONII BIOVAR SOBRIA

The colonization mechanisms of enteropathogenic Aeromonas strains are poorly characterized, but recent studies indicate that some filamentou s structures are intestinal adhesins. This study describes the purific ation and characterization of a long, flexible pilus from a gastroente ritis-associated strain of Aeromonas veronii biovar sobria. SDS-PAGE a nalysis (various conditions) of pill preparations yielded a pilin prot ein band of similar to 21 kDa. Its N-terminal amino acid sequence was unambiguous and homologous with those of type IV pilins. Immunogold el ectron microscopy with rabbit antisera produced against this pilin pro tein (SFP) decorated single pill and rope-like bundles of pill on the bacterial surface. These were seen more frequently on strains grown at 22 degrees C compared with 37 degrees C and in liquid rather than on solid medium. SFP was not detected on any of 104 strains of Aeromonas (different species and sources) from our culture collection, although morphologically similar structures were seen on a number of these stra ins. This finding and differences among other published amino acid seq uences show that Aeromonas type IV pill are antigenically diverse. Bun dle-forming type IV 'class B' pill are important in the virulence of o ther enteropathogenic bacteria. The N-terminal amino acid sequence of the Aeromonas SFP, however, showed closer homology to the type IV 'cla ss A' pilins. Studies are in progress to investigate the role of SFP i n Aeromonas virulence. (C) 1996 Academic Press Limited