Molecular Biogrouping of PathogenicYersinia enterocolitica

The YsrS Paralog DygS Has the Capacity To Activate Expression of the Yersinia enterocolitica Ysa Type III Secretion System

The Yersinia enterocolitica Ysa type III secretion system (T3SS) is associated with intracellular survival, and, like other characterized T3SSs, it is tightly controlled. Expression of the ysa genes is only detected following growth at low temperatures (26°C) and in high concentrations of sodium chloride (290 mM) in the medium. The YsrSTR phosphorelay (PR) system is required for ysa expression and likely responds to NaCl. During our investigations into the Ysr PR system, we discovered that genes YE3578 and YE3579 are remarkably similar to ysrR and ysrS, respectively, and are probably a consequence of a gene duplication event. The amino acid differences between YE3578 and ysrR are primarily clustered into two short regions. The differences between YE3579 and ysrS are nearly all located in the periplasmic sensing domain; the cytoplasmic domains are 98% identical. We investigated whether these paralogs were capable of activating ysa gene expression. We found that the sensor paralog, named DygS, is capable of compensating for loss of ysrS, but the response regulator paralog, DygR, cannot complement a ysrR gene deletion. In addition, YsrR, but not DygR, interacts with the histidine phosphorelay protein YsrT. Thus, DygS likely activates ysa gene expression in response to a signal other than NaCl and provides an example of a phosphorelay system in which two sensor kinases feed into the same regulatory pathway.

IMPORTANCE

All organisms need mechanisms to promote survival in changing environments. Prokaryotic phosphorelay systems are minimally comprised of a histidine kinase (HK) that senses an extracellular stimulus and a response regulator (RR) but can contain three or more proteins. Through gene duplication, a unique hybrid HK was created. We show that, while the hybrid appears to retain all of the phosphorelay functions, it responds to a different signal than the original. Both HKs transmit the signal to the same RR, which activates a promoter that transcribes a set of genes encoding a type III secretion system (T3SS) whose function is not yet evident. The significance of this work lies in finding that two HKs regulate this T3SS, highlighting its importance.

Biopsy interpretation of colonic biopsies when inflammatory bowel disease is excluded

The interpretation of colonic biopsies related to inflammatory conditions can be challenging because the colorectal mucosa has a limited repertoire of morphologic responses to various injurious agents. Only few processes have specific diagnostic features, and many of the various histological patterns reflect severity and duration of the disease. Importantly the correlation with endoscopic and clinical information is often cardinal to arrive at a specific diagnosis in many cases.

Anti-Yersinia antibodies are not associated with microscopic colitis in an American case-control study

BACKGROUND

Microscopic colitis (MC), which consists of lymphocytic colitis and collagenous colitis, may be triggered by gastrointestinal infections. Studies have suggested a relationship between MC and Yersinia enterocolitica infection. We tested this hypothesis in a case-control study of American patients with MC.

METHODS

Serum was collected from 47 patients with MC and 44 age- and gender-matched healthy controls at a large referral center in the mid-western United States. Anti-IgA and IgG antibodies to Y. enterocolitica were measured using an enzyme-linked immunosorbent assay (ELISA). Fisher's exact test was used to assess statistical significance.

RESULTS

There were no differences between the two groups for seroprevalence of anti-Yersinia IgA (cases 2.1%, controls 2.3%, p = 1.00) or IgG antibodies (cases 4.3%, controls 6.8%, p = 0.67). There was no correlation between antibody titers and duration of MC diagnosis.

CONCLUSION

Our data do not support the role of exposure to Y. enterocolitica in an American group of patients with MC.

Interaction of Yersinia with the gut: mechanisms of pathogenesis and immune evasion

Yersinia entercolitica and Yersinia pseudotuberculosis are human foodborne pathogens that interact extensively with tissues of the gut and the host's immune system to cause disease. As part of their pathogenic strategies, the Yersinia have evolved numerous ways to invade host tissues, gain essential nutrients, and evade host immunity. Technological advances over the last 10 years have revolutionized our understanding of host-pathogen interactions. The application of these new technologies has also shown that even well-understood pathogens such as the Yersinia have many surprises waiting to be revealed. The complex interaction with the host has made Yersinia a paradigm for understanding bacterial pathogenesis and the host response to invasive bacterial infections. This review examines the mechanisms of immune evasion employed by the Yersinia and highlights recent advances in understanding the host-pathogen interaction.