| Autor: |
Kirov, Sylvia M., Barnett, Timothy C., Pepe, Cynthia M., Strom, Mark S., Albert, M. John |
| Zdroj: |
Infection and Immunity; July 2000, Vol. 68 Issue: 7 p4040-4048, 9p |
| Abstrakt: |
ABSTRACTAlthough there is substantial evidence that type IV pili purified from diarrhea-associated Aeromonasspecies (designated Bfp for bundle-forming pilus) are intestinal colonization factors (S. M. Kirov, L. A. O'Donovan, and K. Sanderson, Infect. Immun. 67:5447–5454, 1999), nothing is known regarding the function of a second family of Aeromonastype IV pili (designated Tap for type IV Aeromonaspilus), identified following the cloning of a pilus biogenesis gene cluster tapABCD. Related pilus gene clusters are widely conserved among gram-negative bacteria, but their significance for virulence has been controversial. To investigate the role of Tap pili in Aeromonaspathogenesis, mutants ofAeromonasstrains (a fish isolate of A. hydrophilaand a human dysenteric isolate of A. veroniibv. sobria) were prepared by insertional inactivation of the tapAgene which encodes the type IV pilus subunit protein, TapA. Exotoxic activities were unaffected by the mutation intapA. Inactivation of tapAhad no effect on the bacterial adherence of these two isolates to HEp-2 cells. For theA. veroniibv. sobria isolate, adhesion to Henle 407 intestinal cells and to human intestinal tissue was also unaffected. There was no significant effect on the duration of colonization or incidence of diarrhea when the A. veroniibv. sobria strain was tested in the removable intestinal tie adult rabbit diarrhea model or on its ability to colonize infant mice. Evidence was obtained that demonstrated that TapA was expressed by both Aeromonasspecies and was present on the cell surface, although if assembled into pili this pilus type appears to be an uncommon one under standard bacterial growth conditions. Further studies into factors which may influence Tap expression are required, but the present study suggests that Tap pili may not be as significant as Bfp pili forAeromonasintestinal colonization. |
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