Aggregative Adherence and Intestinal Colonization by Enteroaggregative Escherichia coli Are Produced by Interactions among Multiple Surface Factors

• Published in: mSphere 2018-03, Vol.3 (2)
• Main Authors: Blanton, Laura V, Wang, Lawrence T, Hofmann, Jennifer, DuBow, Joshua, Lafrance, Alexander, Kwak, Stephen, Bowers, Levi, Levine, Mandara A, Hale, Charles O, Meneely, Philip M, Okeke, Iruka N
• Format: Article
• Language: English
• Subjects: adherence; Adhesins; aggregative adherence fimbriae; antiaggregative protein; Bacteria; Biofilms; Cell surface; Clonal deletion; Colonization; Colonization factor; Diarrhea; diarrheagenic Escherichia coli; E coli; enteroaggregative Escherichia coli; Escherichia coli; Genes; Genomes; Intestine; Membrane proteins; Nematodes; Pathogens; Phenotypes; Pili; Worms
• ISSN: 2379-5042; 2379-5042
• DOI: 10.1128/msphere.00078-18

Enteroaggregative (EAEC) bacteria are exceptional colonizers that are associated with diarrhea. The genome of EAEC strain 042, a diarrheal pathogen validated in a human challenge study, encodes multiple colonization factors. Notable among them are aggregative adherence fimbriae (AAF/II) and a secreted antiaggregation protein (Aap). Deletion of is known to increase adherence, autoaggregation, and biofilm formation, so it was proposed that Aap counteracts AAF/II-mediated interactions. We hypothesized that Aap sterically masks heat-resistant agglutinin 1 (Hra1), an integral outer membrane protein recently identified as an accessory colonization factor. We propose that this masking accounts for reduced colonization upon deletion and yet no colonization-associated phenotypes when is deleted . Using single and double mutants of , , and the AAF/II structural protein gene , we demonstrated that increased adherence in mutants occurs even when AAF/II proteins are genetically or chemically removed. Deletion of together with abolishes the hyperadherence phenotype, demonstrating that Aap indeed masks Hra1. The presence of all three colonization factors, however, is necessary for optimal colonization and for rapidly building stacked-brick patterns on slides and cultured monolayers, the signature EAEC phenotype. Altogether, our data demonstrate that Aap serves to mask nonstructural adhesins such as Hra1 and that optimal colonization by EAEC is mediated through interactions among multiple surface factors. Enteroaggregative (EAEC) bacteria are exceptional colonizers of the human intestine and can cause diarrhea. Compared to other pathogens, little is known about the genes and pathogenic mechanisms that differentiate EAEC from harmless commensal . EAEC bacteria attach via multiple proteins and structures, including long appendages produced by assembling molecules of AafA and a short surface protein called Hra1. EAEC also secretes an antiadherence protein (Aap; also known as dispersin) which remains loosely attached to the cell surface. This report shows that dispersin covers Hra1 such that the adhesive properties of EAEC seen in the laboratory are largely produced by AafA structures. When the bacteria colonize worms, dispersin is sloughed off, or otherwise removed, such that Hra1-mediated adherence occurs. All three factors are required for optimal colonization, as well as to produce the signature EAEC stacked-brick adherence pattern. Interplay among multiple colonization f