EspH utilizes phosphoinositide and Rab binding domains to interact with plasma membrane infection sites and Rab GTPases.

Enteropathogenic (EPEC) is a Gram-negative bacterial pathogen that causes persistent diarrhea. Upon attachment to the apical plasma membrane of the intestinal epithelium, the pathogen translocates virulence proteins called effectors into the infected cells. These effectors hijack numerous host processes for the pathogen's benefit.

Sensing for survival: specialised regulatory mechanisms of Type III secretion systems in Gram-negative pathogens.

For centuries, Gram-negative pathogens have infected the human population and been responsible for numerous diseases in animals and plants. Despite advancements in therapeutics, Gram-negative pathogens continue to evolve, with some having developed multi-drug resistant phenotypes. For the successful control of infections caused by these bacteria, we need to widen our understanding of the mechanisms of host-pathogen interactions.

Dormant bacterial spores encrypt a long-lasting transcriptional program to be executed during revival.

Sporulating bacteria can retreat into long-lasting dormant spores that preserve the capacity to germinate when propitious. However, how the revival transcriptional program is memorized for years remains elusive. We revealed that in dormant spores, core RNA polymerase (RNAP) resides in a central chromosomal domain, where it remains bound to a subset of intergenic promoter regions.

Discovery of a Novel Inner Membrane-Associated Bacterial Structure Related to the Flagellar Type III Secretion System.

The bacterial flagellar type III secretion system (fT3SS) is a suite of membrane-embedded and cytoplasmic proteins responsible for building the flagellar motility machinery. Homologous nonflagellar (NF-T3SS) proteins form the injectisome machinery that bacteria use to deliver effector proteins into eukaryotic cells, and other family members were recently reported to be involved in the formation of membrane nanotubes. Here, we describe a novel, evolutionarily widespread, hat-shaped structure embedded in the inner membranes of bacteria, of yet-unidentified function, that is present in species containing fT3SS.

Activation of the Type III Secretion System of Enteropathogenic Escherichia coli Leads to Remodeling of Its Membrane Composition and Function.

The cell envelope of Gram-negative bacteria is a complex structure, essential for bacterial survival and for resistance to many antibiotics. Channels that cross the bacterial envelope and the host cell membrane form secretion systems that are activated upon attachment to host, enabling bacteria to inject effector molecules into the host cell, required for bacterium-host interaction. The type III secretion system (T3SS) is critical for the virulence of several pathogenic bacteria, including enteropathogenic Escherichia coli (EPEC).

Escherichia coli O127 group 4 capsule proteins assemble at the outer membrane.

Enteropathogenic Escherichia coli O127 is encapsulated by a protective layer of polysaccharide made of the same strain specific O-antigen as the serotype lipopolysaccharide. Seven genes encoding capsule export functions comprise the group 4 capsule (gfc) operon. Genes gfcE, etk and etp encode homologs of the group 1 capsule secretion system but the upstream gfcABCD genes encode unknown functions specific to group 4 capsule export.

The impact of Hfq-mediated sRNA-mRNA interactome on the virulence of enteropathogenic .

Small RNAs (sRNAs) exert their regulation posttranscriptionally by base pairing with their target mRNAs, often in association with the RNA chaperone protein Hfq. Here, integrating RNA-seq–based technologies and bioinformatics, we deciphered the Hfq-mediated sRNA-target interactome of enteropathogenic (EPEC). The emerging network comprises hundreds of sRNA-mRNA pairs, including mRNAs of virulence-associated genes interacting with known sRNAs encoded within the core genome, as well as with newly found sRNAs encoded within pathogenicity islands.

Binding specificity of type three secretion system effector NleH2 to multi-cargo chaperone CesT and their phosphorylation.

Gram-negative pathogens like Enteropathogenic Escherichia coli (EPEC) utilize the type three secretion system (T3SS) to translocate various effector proteins that are needed to "hijack" the host system for pathogenic survival. Specialized T3SS chaperones inside bacterial cells stabilize these effector proteins and facilitate their translocation. CesT is a unique multi-cargo chaperone that interacts with and translocates ~10 different effector proteins.

Mitochondrial Targeting of the Enteropathogenic Escherichia coli Map Triggers Calcium Mobilization, ADAM10-MAP Kinase Signaling, and Host Cell Apoptosis.

The ability of diarrheagenic bacterial pathogens, such as enteropathogenic (EPEC), to modulate the activity of mitogen-activated protein kinases (MAPKs) and cell survival has been suggested to benefit bacterial colonization and infection. However, our understanding of the mechanisms by which EPEC modulate these functions is incomplete. In this study, we show that the EPEC type III secreted effector Map stimulates the sheddase activity of the disintegrin and metalloproteinase domain-containing protein 10 (ADAM10) and the ERK and p38 MAPK signaling cascades.

The bacterial metalloprotease NleD selectively cleaves mitogen-activated protein kinases that have high flexibility in their activation loop.

Microbial pathogens often target the host mitogen-activated protein kinase (MAPK) network to suppress host immune responses. We previously identified a bacterial type III secretion system effector, termed NleD, a metalloprotease that inactivates MAPKs by specifically cleaving their activation loop. Here, we show that NleDs form a growing family of virulence factors harbored by human and plant pathogens as well as insect symbionts.

Donor-delivered cell wall hydrolases facilitate nanotube penetration into recipient bacteria.

Bacteria can produce membranous nanotubes that mediate contact-dependent exchange of molecules among bacterial cells. However, it is unclear how nanotubes cross the cell wall to emerge from the donor or to penetrate into the recipient cell. Here, we report that Bacillus subtilis utilizes cell wall remodeling enzymes, the LytC amidase and its enhancer LytB, for efficient nanotube extrusion and penetration.

Escherichia coli O-antigen capsule (group 4) is essential for serum resistance.

Many septicemic Escherichia coli strains produce polysaccharide capsules, which are important for survival in serum. Here we show that a septicemic E. coli strain of serotype O78 produce an O-antigen capsule (group 4 capsule) and we show that this capsule is essential for serum survival.

Control of Type III Secretion System Effector/Chaperone Ratio Fosters Pathogen Adaptation to Host-Adherent Lifestyle.

The transition from a planktonic lifestyle to a host-attached state is often critical for bacterial virulence. Upon attachment to host cells, enteropathogenic (EPEC) employs a type III secretion system (T3SS) to inject into the host cells ∼20 effector proteins, including Tir. CesT, which is encoded from the same operon downstream of , is a Tir-bound chaperone that facilitates Tir translocation.

Intraepithelial neutrophils in mammary, urinary and gall bladder infections.

Neutrophil mobilization is a crucial response to protect the host against invading microorganisms. Neutrophil recruitment and removal have to be tightly regulated to prevent uncontrolled inflammation and excessive release of their toxic content causing tissue damage and subsequent organ dysfunctions. We show here the presence of live and apoptotic neutrophils in the cytoplasm of inflamed mammary, urinary and gall bladder epithelial cells following infection with E.

Enteropathogenic Escherichia coli remodels host endosomes to promote endocytic turnover and breakdown of surface polarity.

Enteropathogenic E. coli (EPEC) is an extracellular diarrheagenic human pathogen which infects the apical plasma membrane of the small intestinal enterocytes. EPEC utilizes a type III secretion system to translocate bacterial effector proteins into its epithelial hosts.

A Ubiquitous Platform for Bacterial Nanotube Biogenesis.

We have previously described the existence of membranous nanotubes, bridging adjacent bacteria, facilitating intercellular trafficking of nutrients, cytoplasmic proteins, and even plasmids, yet components enabling their biogenesis remain elusive. Here we reveal the identity of a molecular apparatus providing a platform for nanotube biogenesis. Using Bacillus subtilis (Bs), we demonstrate that conserved components of the flagellar export apparatus (FliO, FliP, FliQ, FliR, FlhB, and FlhA), designated CORE, dually serve for flagellum and nanotube assembly.

Pathogenic E. coli Extracts Nutrients from Infected Host Cells Utilizing Injectisome Components.

Microbiota and intestinal epithelium restrict pathogen growth by rapid nutrient consumption. We investigated how pathogens circumvent this obstacle to colonize the host. Utilizing enteropathogenic E.

Type Three Secretion System-Dependent Microvascular Thrombosis and Ischemic Enteritis in Human Gut Xenografts Infected with Enteropathogenic Escherichia coli.

Enteropathogenic (EPEC) is a leading cause of severe intestinal disease and infant mortality in developing countries. Virulence is mediated by a type three secretion system (T3SS), causing the hallmark attaching and effacing (AE) lesions and actin-rich pedestal formation beneath the infecting bacteria on the apical surface of enterocytes. EPEC is a human-specific pathogen whose pathogenesis cannot be studied in animal models.

Epithelial cells detect functional type III secretion system of enteropathogenic Escherichia coli through a novel NF-κB signaling pathway.

Enteropathogenic Escherichia coli (EPEC), a common cause of infant diarrhea, is associated with high risk of mortality in developing countries. The primary niche of infecting EPEC is the apical surface of intestinal epithelial cells. EPEC employs a type three secretion system (TTSS) to inject the host cells with dozens of effector proteins, which facilitate attachment to these cells and successful colonization.

Host cell attachment elicits posttranscriptional regulation in infecting enteropathogenic bacteria.

The mechanisms by which pathogens sense the host and respond by remodeling gene expression are poorly understood. Enteropathogenic (EPEC), the cause of severe intestinal infection, employs a type III secretion system (T3SS) to inject effector proteins into intestinal epithelial cells. These effectors subvert host cell processes to promote bacterial colonization.

A long-term epigenetic memory switch controls bacterial virulence bimodality.

When pathogens enter the host, sensing of environmental cues activates the expression of virulence genes. Opposite transition of pathogens from activating to non-activating conditions is poorly understood. Interestingly, variability in the expression of virulence genes upon infection enhances colonization.

Age-Dependent Susceptibility to Enteropathogenic Escherichia coli (EPEC) Infection in Mice.

Enteropathogenic Escherichia coli (EPEC) represents a major causative agent of infant diarrhea associated with significant morbidity and mortality in developing countries. Although studied extensively in vitro, the investigation of the host-pathogen interaction in vivo has been hampered by the lack of a suitable small animal model. Using RT-PCR and global transcriptome analysis, high throughput 16S rDNA sequencing as well as immunofluorescence and electron microscopy, we characterize the EPEC-host interaction following oral challenge of newborn mice.