Structural alterations in a type IV pilus subunit protein result in concurrent defects in multicellular behaviour and adherence to host tissue

Abstract

The ability of bacteria to establish complex communities on surfaces is believed to require both bacterial–substratum and bacterial–bacterial interactions, and type IV pili appear to play a critical but incompletely defined role 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 unique selective scheme. The mutants, carrying single amino acid substitutions within the conserved amino‐terminal domain of the pilus fibre subunit, were reduced in the ability to adhere to a human epithelial cell line. Co‐expression of the altered alleles in the context of a wild‐type pilE gene confirmed that they were dominant negative with respect to aggregation and human cell adherence. Strains expressing two copies of the altered alleles produced twice as much purifiable pili but retained the aggregative and adherence defects. Finally, the defects in aggregative behaviour and adherence of each of the mutants were suppressed by a loss‐of‐function mutation in the twitching motility gene pilT. The correlations between self‐aggregation and the net capacity of the microbial population to adhere efficiently demonstrates the potential significance of bacterial cell–cell interactions to colonization.

Identification of Diverse Archaeal Proteins with Class III Signal Peptides Cleaved by Distinct Archaeal Prepilin Peptidases

“…Dis-tinct from poorly conserved amino acid sequences in the hydrophobic stretches of Tat and class I/II Sec signal sequences, the sequence of the hydrophobic stretch in the signal sequences of archaeal flagellins is highly conserved. This has also been observed for type IV pilins (12) and presumably allows optimal subunit-subunit interaction (11,29). Consistent with the requirement for a highly conserved N-terminal hydrophobic "assembly domain," several orthologous groups of FlaFind positives and substrates encoded by genes that cluster together share substantial sequence homology at their N termini (see Fig.…”

Microarray Analyses of Xylella fastidiosa Provide Evidence of Coordinated Transcription Control of Laterally Transferred Elements

“…Cell wall-and outer membrane-related structural components also accounted for significant differences among the tested strains. Particularly noteworthy is the observation of differences among fimbrillin genes, whose products may establish direct contacts with host cells and other bacteria (Park et al 2001). One fimbrillin (ORF XF0539) was not found in the strains obtained from elm and plum, whereas the almond, grape, mulberry, and ragweed isolates lacked four of the fimbrillin genes from strain 9a5c (ORFs XF0487, XF0538, XF0539, and XF1791).…”

Neisseria gonorrhoeae RecQ Helicase HRDC Domains Are Essential for Efficient Binding and Unwinding of the pilE Guanine Quartet Structure Required for Pilin Antigenic Variation

“…The N. gonorrhoeae type IV pilus is essential for establishing infection (2). Pili assist in epithelial adherence and gonococcal cell aggregation and also mediate twitching motility (3)(4)(5). Protective immunity never develops, partially because the bacterium can evade host immune selection by antigenically varying surface antigens, including lipooligosaccharides, the opacity family of outer membrane proteins, and the type IV pilus (6)(7)(8)(9)(10).…”

“…Since the N. gonorrhoeae RecQ helicase HRDC domains are required for efficient levels of pilin Av, we determined whether these domains facilitate the interaction of RecQ helicase with the pilE G4. 3 ; all from Sigma] at 37°C in 5% CO 2 ; when applicable, 1 mM IPTG (isopropyl-␤-D-thiogalactopyranoside) was added for induction. Gonococcal transformants were selected on media containing 80 g/ml kanamycin, 10 g/ml erythromycin, or 2 g/ml tetracycline.…”