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Enteropathogenic Escherichia coli (EPEC) remains a significant cause of infant diarrheal illness and associated morbidity and mortality in developing countries. EPEC strains are characterized by their ability to colonize the small intestines of their hosts by a multistep program involving initial loose attachment to intestinal epithelial cells followed by an intimate adhesion phase. The initial loose interaction of typical EPEC with host intestinal cells is mediated by bundle-forming pili (BFP). BFP are type 4b pili (T4bP) based on structural and functional properties shared with T4bP expressed by other bacteria. The major structural subunit of BFP is called bundlin, a T4b pilin expressed from the bfpA gene in the BFP operon, which contains three additional genes that encode the pilin-like proteins BfpI, BfpJ, and BfpK. In this study, we show that, in the absence of the BFP retraction ATPase (BfpF), BfpI, BfpJ, and BfpK are dispensable for BFP biogenesis. We also demonstrate that these three minor pilins are incorporated along with bundlin into the BFP filament and contribute to its structural integrity and host cell adhesive properties. The results confirm that previous findings in T4aP systems can be extended to a model T4bP such as BFP. [ABSTRACT FROM AUTHOR]

Background Autotransporter proteins represent a treasure trove for molecular engineers who modify Gram-negative bacteria for the export or secretion of foreign proteins across two membrane barriers. A particularly promising direction is the development of autotransporters as antigen display or secretion systems. Immunologists have been using ovalbumin as a reporter antigen for years and have developed sophisticated tools to detect specific T cells that respond to ovalbumin. Although ovalbumin-expressing bacteria are being used to trace T cell responses to colonizing or invading pathogens, current constructs for ovalbumin presentation have not been optimized. Results The activation of T helper cells in response to ovalbumin was improved by displaying the OVA-CD4 reporter epitope as a multimer on the surface of Salmonella and fused to the autotransporter MisL. Expression was optimized by including tandem in vivo promoters and two post-segregational killing systems for plasmid stabilization. Conclusions The use of an autotransporter protein to present relevant epitope repeats on the surface of bacteria, combined with additional techniques favoring stable and efficient in vivo transcription, optimizes antigen presentation to T cells. The technique of multimeric epitope surface display should also benefit the development of new Salmonella or other enterobacterial vaccines. [ABSTRACT FROM AUTHOR]

This corrects the article DOI: 10.1038/ncomms9754 [ABSTRACT FROM AUTHOR]

Unlabelled: Enteropathogenic Escherichia coli (EPEC) remains a significant cause of infant diarrheal illness and associated morbidity and mortality in developing countries. EPEC strains are characterized by their ability to colonize the small intestines of their hosts by a multistep program involving initial loose attachment to intestinal epithelial cells followed by an intimate adhesion phase. The initial loose interaction of typical EPEC with host intestinal cells is mediated by bundle-forming pili (BFP). BFP are type 4b pili (T4bP) based on structural and functional properties shared with T4bP expressed by other bacteria. The major structural subunit of BFP is called bundlin, a T4b pilin expressed from the bfpA gene in the BFP operon, which contains three additional genes that encode the pilin-like proteins BfpI, BfpJ, and BfpK. In this study, we show that, in the absence of the BFP retraction ATPase (BfpF), BfpI, BfpJ, and BfpK are dispensable for BFP biogenesis. We also demonstrate that these three minor pilins are incorporated along with bundlin into the BFP filament and contribute to its structural integrity and host cell adhesive properties. The results confirm that previous findings in T4aP systems can be extended to a model T4bP such as BFP., Importance: Bundle-forming pili contribute to the host colonization strategy of enteropathogenic Escherichia coli. The studies described here investigate the role for three minor pilin subunits in the structure and function of BFP in EPEC. The studies also suggest that these subunits could be antigens for vaccine development., (Copyright © 2016 Martinez de la Peña et al.)

Understanding the molecular parameters that regulate cross-species transmission and host adaptation of potential pathogens is crucial to control emerging infectious disease. Although microbial pathotype diversity is conventionally associated with gene gain or loss, the role of pathoadaptive nonsynonymous single-nucleotide polymorphisms (nsSNPs) has not been systematically evaluated. Here, our genome-wide analysis of core genes within Salmonella enterica serovar Typhimurium genomes reveals a high degree of allelic variation in surface-exposed molecules, including adhesins that promote host colonization. Subsequent multinomial logistic regression, MultiPhen and Random Forest analyses of known/suspected adhesins from 580 independent Typhimurium isolates identifies distinct host-specific nsSNP signatures. Moreover, population and functional analyses of host-associated nsSNPs for FimH, the type 1 fimbrial adhesin, highlights the role of key allelic residues in host-specific adherence in vitro. Together, our data provide the first concrete evidence that functional differences between allelic variants of bacterial proteins likely contribute to pathoadaption to diverse hosts.