Dynamic interactions of a conserved enterotoxigenic Escherichia coli adhesin with intestinal mucins govern epithelium engagement and toxin delivery

At present, there is no vaccine for enterotoxigenic Escherichia coli (ETEC), an important cause of diarrheal illness. Nevertheless, recent microbial pathogenesis studies have identified a number of molecules produced by ETEC that contribute to its virulence and are novel antigenic targets to complement canonical vaccine approaches. EtpA is a secreted two-partner adhesin that is conserved within the ETEC pathovar. EtpA interacts with the tips of ETEC flagella to promote bacterial adhesion, toxin delivery, and intestinal colonization by forming molecular bridges between the bacteria and the epithelial surface. However, the nature of EtpA interactions with the intestinal epithelium remains poorly defined. Here, we demonstrate that EtpA interacts with glycans presented by transmembrane and secreted intestinal mucins at epithelial surfaces to facilitate pathogen-host interactions that culminate in toxin delivery. Moreover, we found that a major effector molecule of ETEC, the heat-labile enterotoxin (LT), may enhance these interactions by stimulating the production of the gel-forming mucin MUC2. Our studies suggest, however, that EtpA participates in complex and dynamic interactions between ETEC and the gastrointestinal mucosae in which host glycoproteins promote bacterial attachment while simultaneously limiting the epithelial engagement required for effective toxin delivery. Collectively, these data provide additional insight into the intricate nature of ETEC interactions with the intestinal epithelium that have potential implications for rational approaches to vaccine design

Induction of daptomycin resistance in <i>Paenibacillus lautus</i> LC231.

<p>LC231 was cultured in TSB supplemented with 1.25 mM CaCl₂ and 4 µg/ml daptomycin added from start (zero time point) (1) or early log phase (2). Growth was compared to growth control with no drug (3). Arrow represents the time point at which daptomycin was added during early log phase.</p

Resistance levels of Lechuguilla cave bacteria at 20 µg/ml against various antibiotics: (top) Gram-positive strains (bottom) Gram-negative strains.

<p>Antibiotics are grouped according to their mode of action/target, where each color represents a different target.</p

Kinetic parameters for MPH (2′)-II from <i>B. paraconglomeratum.</i>

<p>1- GTP held at 200 µM for antibiotic substrates, 2-erythomycin held at 400 µM.</p

Summary of Antibiotic Inactivation Studies for Gram-Negative Isolates.

<p>Strains were grown in 50% TSB for 5 days in presence of 20 µg/ml antibiotic. Conditional media was used for setting up disk diffusion assays and LC-MS analyses. Inactivation was defined as the absence of a zone of clearance around the disk. Hydrolytic mechanism of ß-lactam resistance is inferred.</p

Plan and profile maps of Lechuguilla Cave, Carlsbad Caverns National Park, New Mexico.

<p>The sites where microbial strains were collected (LCECE, LCDS1 and LCEA1) are shown relative to the entrance and depth. tN represents true North on the plan, while the profile has an exaggerated vertical profile of 1.5×.</p

Expression of the Blood-Group-Related Gene <i>B4galnt2</i> Alters Susceptibility to <i>Salmonella</i> Infection

<div><p>Glycans play important roles in host-microbe interactions. Tissue-specific expression patterns of the blood group glycosyltransferase β-1,4-N-acetylgalactosaminyltransferase 2 (<i>B4galnt2</i>) are variable in wild mouse populations, and loss of <i>B4galnt2</i> expression is associated with altered intestinal microbiota. We hypothesized that variation in <i>B4galnt2</i> expression alters susceptibility to intestinal pathogens. To test this, we challenged mice genetically engineered to express different <i>B4galnt2</i> tissue-specific patterns with a <i>Salmonella</i> Typhimurium infection model. We found <i>B4galnt2</i> intestinal expression was strongly associated with bacterial community composition and increased <i>Salmonella</i> susceptibility as evidenced by increased intestinal inflammatory cytokines and infiltrating immune cells. Fecal transfer experiments demonstrated a crucial role of the <i>B4galnt2</i>-dependent microbiota in conferring susceptibility to intestinal inflammation, while epithelial <i>B4galnt2</i> expression facilitated epithelial invasion of <i>S</i>. Typhimurium. These data support a critical role for <i>B4galnt2</i> in gastrointestinal infections. We speculate that <i>B4galnt2</i>-specific differences in host susceptibility to intestinal pathogens underlie the strong signatures of balancing selection observed at the <i>B4galnt2</i> locus in wild mouse populations.</p></div