Hsm. Park et al., Structural alterations in a type IV pilus subunit protein result in concurrent defects in multicellular behaviour and adherence to host tissue, MOL MICROB, 42(2), 2001, pp. 293-307
The ability of bacteria to establish complex communities on surfaces is bel
ieved to require both bacterial-substratum and bacterial-bacterial interact
ions, and type IV pill appear to play a critical but incompletely defined r
ole in both these processes. Using the human pathogen Neisseria gonorrhoeae
, spontaneous mutants defective in bacterial self-aggregative behaviour but
quantitatively unaltered in pilus fibre expression were isolated by a uniq
ue selective scheme. The mutants, carrying single amino acid substitutions
within the conserved aminoterminal domain of the pilus fibre subunit, were
reduced in the ability to adhere to a human epithelial cell line. Co-expres
sion of the altered alleles in the context of a wild-type pilE gene confirm
ed that they were dominant negative with respect to aggregation and human c
ell adherence. Strains expressing two copies of the altered alleles produce
d twice as much purifiable pili but retained the aggregative and adherence
defects. Finally, the defects in aggregative behaviour and adherence of eac
h of the mutants were suppressed by a loss-of-function mutation in the twit
ching motility gene pilT. The correlations between self-aggregation and the
net capacity of the microbial population to adhere efficiently demonstrate
s the potential significance of bacterial cell-cell interactions to coloniz
ation.