Skopova, K. | Search bioRxiv

bioRxiv2026

C-terminal domain of the filamentous hemagglutinin FhaB is crucial for interaction of Bordetella pertussis with ciliated epithelial cells

Bordetella pertussis, the causative agent of whooping cough, produces a [~]370 kDa filamentous hemagglutinin FhaB that serves as a major bacterial adhesin in airway infection. FhaB is secreted via a two-partner secretion pathway and under in vitro culture conditions it is proteolytically processed to the shed [~]230 kDa FHA antigen used currently in acellular pertussis vaccines. We show that FhaB remains largely unprocessed during B. pertussis adhesion to ciliated airway epithelial cells and that its C-terminal domain (CT) is essential for the adhesin function of FhaB. CT deletion did not affect FhaB folding, secretion, or surface exposure, but abolished B. pertussis adhesion to primary human nasal ciliated epithelial cells, thus preventing bacterial colonization of the nasal mucosa and shedding and transmission of the pathogen in a murine nasal infection model. In situ cryo-electron tomography revealed a structural reorganization of the FhaB filaments upon contact with the cilia, presumably due to export of the CT from bacterial periplasm and its subsequent delivery across the ciliary membrane. These findings establish the CT of FhaB as a critical determinant of upper airway colonization by B. pertussis and identify the unprocessed FhaB as the biologically relevant adhesin form involved in airway infection. The revised model of FhaB biogenesis underpins its unique mode of action in pertussis pathogenesis and makes the CT domain to a candidate antigen for future pertussis vaccines.

microbiology↗

bioRxiv2024

A highly conserved sRNA downregulates multiple genes, including a sigma54 transcriptional activator, in the virulence mode of Bordetella pertussis

Bacterial sRNAs together with the RNA chaperone Hfq post-transcriptionally regulate gene expression by affecting ribosome binding or mRNA stability. In the human pathogen Bordetella pertussis, the causative agent of whooping cough, hundreds of sRNAs have been identified, but their roles in B. pertussis biology are mostly unknown. Here we characterize a Hfq-dependent sRNA (S17), whose level is dramatically higher in the virulence (Bvg+) mode. We show that transcription from a {sigma}A-dependent promoter yields a long form of 190 nucleotides (nts) that is processed by RNase E to generate a shorter, more stable form (S17S) of 67 nts. Using RNA-seq and RT-qPCR, we identify 92 genes whose expression significantly increases in the absence of S17. Of these genes, 70 contain sequences at/near their ribosome binding sites (RBSs) that are complementary to single-stranded (ss) regions (Sites 1 or 2) of S17S. The identified genes include those encoding multiple transporters and 3 transcriptional regulators. Using a lacZ translational reporter system, we demonstrate that S17S directly represses one of these genes, BP2158, a {sigma}54- dependent transcriptional regulator, suggesting the repression of a {sigma}54 regulon in the Bvg+ mode. We find that the S17S region containing Sites 1 and 2 is 100% conserved throughout various Betaproteobacteria species, and the S17S target sites are often conserved in the homologs of the B. pertussis target genes. We speculate that S17S regulation represents a highly conserved process that fine-tunes gene expression in the Bvg+ mode of B. pertussis and perhaps under other conditions in related bacteria. IMPORTANCERegulation of gene expression involves controlling transcription, translation, and transcript degradation. sRNAs with short sequences complementary to an mRNA sequence are involved in post-transcriptional regulation by aiding or interfering with either ribosome binding or nuclease attack. In the human pathogen Bordetella pertussis, the causative agent of whooping cough, hundreds of sRNA have been identified, but their functions remain largely unknown. We have characterized a sRNA that is abundant in the virulence mode of B. pertussis and serves to down-regulate multiple genes including transcriptional regulators and various transporters. We demonstrate that this sRNA directly represses a transcriptional factor, suggesting that it influences the regulation of specific B. pertussis regulons. The high conservation of this sRNA and its targets within Betaproteobacteria suggests a conserved pathway for gene regulation.

microbiology↗