Frontiers in Microbiology (Jul 2015)
A PAS Domain-Containing Regulator Controls Flagella-Flagella Interactions in Campylobacter jejuni
Abstract
The bipolar flagella of the foodborne bacterial pathogen Campylobacter jejuni confermotility, which is essential for virulence. The flagella of C. jejuni are posttranslationallymodified, but how this process is controlled is not well understood. Inthis work, we have identified a novel PAS-domain containing regulatory system, whichmodulates flagella-flagella interactions in C. jejuni. Inactivation of the cj1387c gene,encoding a YheO-like PAS6 domain linked to a helix-turn-helix domain, resulted in thegeneration of a tightly associated 'cell-train' morphotype, where up to four cells wereconnected by their flagella. The morphotype was fully motile, resistant to vortexing,accompanied by increased autoagglutination, and was not observed in aflagellated cells.The Δcj1387c mutant displayed increased expression of the adjacent Cj1388 protein,which comprises of a single endoribonuclease L-PSP domain. Comparative genomicsshowed that cj1387c (yheO) orthologs in bacterial genomes are commonly linked to anadjacent cj1388 ortholog, with some bacteria, including C. jejuni, containing anothercj1388-like gene (cj0327). Inactivation of the cj1388 and cj0327 genes resulted indecreased autoagglutination in Tween-20-supplemented media. The Δcj1388 andΔcj0327 mutants were also attenuated in a Galleria larvae-based infection model.Finally, substituting the sole cysteine in Cj1388 for serine prevented Cj1388dimerisation in non-reducing conditions, and resulted in decreased autoagglutination inthe presence of Tween-20. We hypothesize that Cj1388 and Cj0327 modulate posttranslationalmodification of the flagella through yet unidentified mechanisms, andpropose naming Cj1387 the Campylobacter Flagella Interaction Regulator CfiR, andthe Cj1388 and Cj0327 protein as CfiP and CfiQ, respectively.
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