The H-NS protein silences the pyp regulatory network of Yersinia enterocolitica and is involved in controlling biofilm formation.

Horizontal gene transfer plays an important role in bacterial evolution. DNA acquired by horizontal gene transfer has to be incorporated into existing regulatory networks. The histone-like nucleoid structuring protein H-NS acts as a silencer of horizontally acquired genes to avoid potential damage.

Type II secretion in Yersinia-a secretion system for pathogenicity and environmental fitness.

In Yersinia species, type III secretion (T3S) is the most prominent and best studied secretion system and a hallmark for the infection process of pathogenic Yersinia species. Type II secretion (T2S), on the other hand, is less well-characterized, although all Yersinia species, pathogenic as well as non-pathogenic, possess one or even two T2S systems. The only Yersinia strain in which T2S has so far been studied is the human pathogenic strain Y.

A newly identified bacterial cell-penetrating peptide that reduces the transcription of pro-inflammatory cytokines.

Cell-permeable proteins, also called cell-penetrating peptides (CPPs), have the ability to cross cellular membranes, either alone or in association with bioactive cargo. We identified the Yersinia protein YopM as a novel bacterial cell-permeable protein. Here, we describe the ability of isolated recombinant YopM to enter host cells without a requirement for additional factors.

Transcriptional activation of the tad type IVb pilus operon by PypB in Yersinia enterocolitica.

Type IV pili are virulence factors in various bacteria and mediate, among other functions, the colonization of diverse surfaces. Various subclasses of type IV pili have been identified, but information on pilus expression, biogenesis, and the associated phenotypes is sparse for the genus Yersinia. We recently described the identification of PypB as a transcriptional regulator in Yersinia enterocolitica.

Transcriptional regulation of the Yts1 type II secretion system of Yersinia enterocolitica and identification of secretion substrates.

Type II secretion systems (T2SSs) mediate the transport of proteins through the bacterial outer membrane. Although widespread in gamma-proteobacteria, they have so far not been characterized in the human pathogen Yersinia enterocolitica. We describe here genetic linkage of the Yts1 and Yts2 T2SSs with a transcriptional regulator in the highly pathogenic Y.

Controlled activation of the Cpx system is essential for growth of Yersinia enterocolitica.

The Cpx two-component signal transduction system regulates the expression of genes in response to stimuli associated with the maintenance of the bacterial cell envelope. Additionally, the Cpx system is important for virulence in several bacterial pathogens. In this study, we analyzed the Cpx system of the human enteropathogen Yersinia enterocolitica.

Identification and characterization of Ibe, a novel type III effector protein of A/E pathogens targeting human IQGAP1.

Enteropathogenic Escherichia coli (EPEC), atypical enteropathogenic Escherichia coli (ATEC) and enterohemorrhagic Escherichia coli (EHEC) belong to the family of attaching and effacing (A/E) pathogens. Pathogenicity is mediated by subversion of host cell functions involving type III secretion system (TTSS)-dependent effector proteins. In this study, we have identified and characterized a novel TTSS-dependent effector protein encoded at the 5'-end of the locus of enterocyte effacement (LEE) pathogenicity island (PAI) of ATEC strain 3431-4/86 (O8:H(-)).

A regulatory network controls expression of the in vivo-expressed HreP protease of Yersinia enterocolitica.

The human enteropathogen Yersinia enterocolitica survives and replicates in the lymphoid tissues of its host. Previous in vivo analyses of gene expression revealed that various chromosomal genes are expressed at this stage of infection, but not in vitro. One of these, termed hreP, encodes a protease that is necessary for full virulence of Y.

Resistance of chemokine receptor 6-deficient mice to Yersinia enterocolitica infection: evidence of defective M-cell formation in vivo.

M cells, specialized cells within Peyer's patches (PPs), are reduced in number in chemokine receptor 6 (CCR6)-deficient mice. The pathogenic microorganism Yersinia enterocolitica exploits M cells for the purpose of mucosal tissue invasion exclusively through PPs. The aim of this study was to evaluate the course of yersiniosis in CCR6-deficient mice and to investigate whether these mice might be used as an in vivo model to determine M-cell function.

Overproduction of DNA adenine methyltransferase alters motility, invasion, and the lipopolysaccharide O-antigen composition of Yersinia enterocolitica.

DNA adenine methyltransferase (Dam) not only regulates basic cellular functions but also interferes with the proper expression of virulence factors in various pathogens. We showed previously that for the human pathogen Yersinia enterocolitica, overproduction of Dam results in increased invasion of epithelial cells. Since invasion and motility are coordinately regulated in Y.

Identification of unconventional intestinal pathogenic Escherichia coli isolates expressing intermediate virulence factor profiles by using a novel single-step multiplex PCR.

Intestinal pathogenic Escherichia coli represents a global health problem for mammals, including humans. At present, diarrheagenic E. coli bacteria are grouped into seven major pathotypes that differ in their virulence factor profiles, severity of clinical manifestations, and prognosis.

DNA adenine methylation and bacterial pathogenesis.

Methylation of DNA by the DNA adenine methyltransferase (Dam) provides an epigenetic signal that influences and regulates numerous physiological processes in the bacterial cell including chromosome replication, mismatch repair, transposition, and transcription. A growing number of reports describe a role for DNA adenine methylation in regulating the expression of various bacterial genes related to virulence in diverse pathogens, suggesting that DNA methylation may be a widespread and versatile regulator of virulence gene expression. Here, we summarize the current knowledge about the influence of DNA methylation on virulence functions and discuss perspectives for future research.

Altered Ca(2+) regulation of Yop secretion in Yersinia enterocolitica after DNA adenine methyltransferase overproduction is mediated by Clp-dependent degradation of LcrG.

DNA methylation by the DNA adenine methyltransferase (Dam) interferes with the coordinated expression of virulence functions in an increasing number of pathogens. While analyzing the effect of Dam on the virulence of the human pathogen Yersinia enterocolitica, we observed type III secretion of Yop effector proteins under nonpermissive conditions. Dam alters the Ca(2+) regulation of Yop secretion but does not affect the temperature regulation of Yop/Ysc expression.

Pertussis toxin transiently affects barrier integrity, organelle organization and transmigration of monocytes in a human brain microvascular endothelial cell barrier model.

Encephalopathies and neurological disorders are sometimes associated with respiratory tract infections caused by Bordetella pertussis. For these complications to occur cerebral barriers have to be compromised. Therefore, the influence of pertussis toxin (PT), a decisive virulence determinant of B.

Rapid identification and differentiation of clinical isolates of enteropathogenic Escherichia coli (EPEC), atypical EPEC, and Shiga toxin-producing Escherichia coli by a one-step multiplex PCR method.

Enteropathogenic Escherichia coli (EPEC), atypical enteropathogenic E. coli, and Shiga toxin-producing E. coli differ in their virulence factor profiles, clinical manifestations, and prognosis, and they require different therapeutic measures.

YopM of Yersinia enterocolitica specifically interacts with alpha1-antitrypsin without affecting the anti-protease activity.

It was previously shown that alpha1-antitrypsin (AAT) interacts with the type III secreted (T3S) EspB and EspD proteins of enteropathogenic Escherichia coli (EPEC), resulting in reduced functionality of the proteins. To determine if AAT is also able to interact with T3S proteins of other pathogens, the binding of AAT to Yop proteins of Yersinia enterocolitica was analysed. AAT did not interact with YopB or YopD, which have functions in type III translocation similar to EspB and EspD in EPEC, but specifically interacts with YopM, a member of the leucine-rich repeat (LRR) family of proteins, in overlay and pull-down assays.

Esp-independent functional integration of the translocated intimin receptor (Tir) of enteropathogenic Escherichia coli (EPEC) into host cell membranes.

The pathogenesis of enteropathogenic Escherichia coli (EPEC) is characterized by the type III secretion system-dependent exploitation of target cells that results in attaching and effacing (A/E) lesions, actin rearrangements and pedestal formation. This pathology is mediated by effector proteins which are translocated by the type III secretion system into the host cell such as the translocated intimin receptor (Tir) and several E. coli secreted proteins (Esp).

DNA methylation in Yersinia enterocolitica: role of the DNA adenine methyltransferase in mismatch repair and regulation of virulence factors.

DNA adenine methyltransferase (Dam) plays an important role in physiological processes of Gram-negative bacteria such as mismatch repair and replication. In addition, Dam regulates the expression of virulence genes in various species. The authors cloned the dam gene of Yersinia enterocolitica and showed that Dam is essential for viability.

Alpha 1-antitrypsin binds to and interferes with functionality of EspB from atypical and typical enteropathogenic Escherichia coli strains.

Enteropathogenic Escherichia coli (EPEC), including diffusely adhering atypical E. coli, strains use a type III secretion system to deliver effector proteins into the membrane and cytoplasm of infected cells. The E.

Regulation of htrA expression in Yersinia enterocolitica.

In Escherichia coli, envelope stress is regulated by the alternative sigma factor sigma(E) and the two-component regulatory system CpxRA. Both systems overlap in the transcriptional regulation of the htrA gene encoding a protease that degrades misfolded proteins in the periplasm. In Yersinia enterocolitica, HtrA is important for intracellular survival and full virulence in animal models.

Identification of rpoE and nadB as host responsive elements of Yersinia enterocolitica.

We describe the identification of the Yersinia enterocolitica rpoE gene, which encodes the alternative sigma factor sigmaE, and the divergently transcribed nadB gene, as genes that are expressed during infection of mice. As in Escherichia coli, rpoE of Y. enterocolitica is essential for growth and its expression is autoregulated.

Differential modulation by Ca2+ of type III secretion of diffusely adhering enteropathogenic Escherichia coli.

Enteropathogenic Escherichia coli (EPEC) strains are a common cause of persistent diarrhea among infants, primarily in developing countries. The pathogenicity of EPEC is associated with the expression and secretion of bacterial proteins encoded by the chromosomal locus of enterocyte effacement (LEE). The LEE-encoded type III-secreted proteins EspA, EspB, and EspD are part of a molecular syringe, which is used by EPEC to translocate effector proteins directly into the cytoplasm of host cells.