Pili of Aeromonas hydrophila: Purification, Characterization, and Biological Role

Abstract

Aeromonas hydrophila (Ae6) has 2 morphologically distinctive kinds of pili. One appeared rigid, channeled, and straight with a diameter of 9 nm (Ae6-R pili). The other looked flexible, wavy, and having helical structure with a diameter of 7 nm (Ae6-W pili). Ae6-R pili were purified and characterized.The pili consisted of a subunit protein with a molecular weight of 18 kDa as estimated by SDS-PAGE, and contained 42.3% hydrophobic amino acids and one cysteine residue.The pilus was solubilized to 18 kDa subunit protein by 2-mercaptoethanol.dithiothreitol, hydrochloric acid, or heating at 120 C for 5 min. The organism Ae6 was strongly adhesive to rabbit intestines as well as human intestines, and agglutinated erythrocytes. Anti-pili antibody (Fab fraction) did not block the adhesion. Purified Ae6-R pili did not adhere to the intestine or to the erythrocytes.However, the anti-pili Fab inhibited pellicle formation of the organisms cultured in broth, and also inhibited salt agglutination with ammonium sulfate.From these results, Ae6-R pili are not likely a colonization factor but probably play a role in the autoaggregation of the organisms.

Investigation of the Role of Type IV Aeromonas Pilus (Tap) in the Pathogenesis of Aeromonas Gastrointestinal Infection

“…sobria strain BC88, adherence to the intestinal cell line (Henle 407) and intestinal tissue was also not significantly different for the wild type and for the tapA mutant strain. Since type I and Bfp pili are the predominant pilus types seen on these bacterial strains (17,30), this result may not be entirely unexpected. Experiments aimed at visualizing Tap pili on the bacterial cell surface by IEM were not successful, despite the growth of A. veronii bv.…”

“…IEM with anti-TapA serum could not establish whether any of the filamentous structures were Tap pili and, hence, whether they were missing in mutant strains (data not shown). Previous studies with A. hydrophila isolates have shown that the vast majority of pili on the surface of this species are "short-rigid," type I pili (13,17,28).…”

“…sobria and A. caviae grown under standard in vitro conditions is the bundle-forming pilus (Bfp) (30,31). Bfp pili have also been isolated from a strain of A. hydrophila, but fecal isolates of this species are often heavily piliated and express numerous type I pili (17). Bfp pili exhibit N-terminal sequence homology with the mannose-sensitive hemagglutinin pilus of V. cholerae.…”

The pili of Aeromonas hydrophila: identification of an environmentally regulated "mini pilin".

“…Moreover, they biochemically and functionally resemble pili isolated from clinical strains of A . hydrophila from Japan and Thailand ; these pili did not agglutinate rabbit, human, and guinea pig erythrocytes, and like the straight pili reported here, were comprised of a 17,000-mol wt subunit (14,26). The apparent association of straight pili with strains from diverse geographic locations suggests that this pilus type is expressed by most clinical and environmental strains of A .…”

“…More recently, ultrastructural examination ofA. hydrophila and the related species A. sobria have revealed the existence of two types of pilus filaments that could be distinguished by morphologic criteria (13,14). Strains expressing one of these pilus types adhere to the HEp-2 cell line, raising the possibility that the colonization of host epithelial surfaces might be mediated by this pilus type.…”