Protozoan-Priming and Magnesium Conditioning Enhance Dissemination and Monochloramine Resistance.

Opportunistic pathogens (OPs) are of concern in drinking water distribution systems because they persist despite disinfectant residuals. While many OPs garner protection from disinfectants via a biofilm lifestyle, () also gains disinfection resistance by being harbored within free-living amoebae (FLA). It has been long established, but poorly understood, that grown within FLA show increased infectivity toward subsequent FLA or human cells (i.

Identification of Conserved ABC Importers Necessary for Intracellular Survival of in Multiple Hosts.

It is established that the human pathogen becomes significantly augmented for infection of macrophages after intracellular growth in amoebae when compared to like-strains cultivated in laboratory media. Based on this observation, we reasoned that the most critical virulence determinants of . are expressed by responding to stimuli generated by the protozoan host specifically; a process we term "protozoan-priming.

Identification of Novel Host Interactors of Effectors Secreted by and .

Many pathogenic bacteria of the family use type III secretion systems to inject virulence proteins, termed "effectors," into the host cell cytosol. Although host-cellular activities of several effectors have been demonstrated, the function and host-targeted pathways of most of the effectors identified to date are largely undetermined. To gain insight into host proteins targeted by bacterial effectors, we performed coaffinity purification of host proteins from cell lysates using recombinant effectors from the intracellular pathogens serovar Typhimurium and .

ChIP-Seq Analysis of the σE Regulon of Salmonella enterica Serovar Typhimurium Reveals New Genes Implicated in Heat Shock and Oxidative Stress Response.

The alternative sigma factor σE functions to maintain bacterial homeostasis and membrane integrity in response to extracytoplasmic stress by regulating thousands of genes both directly and indirectly. The transcriptional regulatory network governed by σE in Salmonella and E. coli has been examined using microarray, however a genome-wide analysis of σE-binding sites in Salmonella has not yet been reported.

Coxiella burnetii and Leishmania mexicana residing within similar parasitophorous vacuoles elicit disparate host responses.

Coxiella burnetii is a bacterium that thrives in an acidic parasitophorous vacuole (PV) derived from lysosomes. Leishmania mexicana, a eukaryote, has also independently evolved to live in a morphologically similar PV. As Coxiella and Leishmania are highly divergent organisms that cause different diseases, we reasoned that their respective infections would likely elicit distinct host responses despite producing phenotypically similar parasite-containing vacuoles.

Identification of Salmonella Typhimurium Deubiquitinase SseL Substrates by Immunoaffinity Enrichment and Quantitative Proteomic Analysis.

Ubiquitination is a key protein post-translational modification that regulates many important cellular pathways and whose levels are regulated by equilibrium between the activities of ubiquitin ligases and deubiquitinases. Here, we present a method to identify specific deubiquitinase substrates based on treatment of cell lysates with recombinant enzymes, immunoaffinity purification, and global quantitative proteomic analysis. As a model system to identify substrates, we used a virulence-related deubiquitinase, SseL, secreted by Salmonella enterica serovar Typhimurium into host cells.

Analysis of the Salmonella regulatory network suggests involvement of SsrB and H-NS in σ(E)-regulated SPI-2 gene expression.

The extracytoplasmic functioning sigma factor σ(E) is known to play an essential role for Salmonella enterica serovar Typhimurium to survive and proliferate in macrophages and mice. However, its regulatory network is not well-characterized, especially during infection. Here we used microarray to identify genes regulated by σ(E) in Salmonella grown in three conditions: a nutrient-rich condition and two others that mimic early and late intracellular infection.

Global analysis of Salmonella alternative sigma factor E on protein translation.

The alternative sigma factor E (σ(E)) is critical for response to extracytoplasmic stress in Salmonella. Extensive studies have been conducted on σ(E)-regulated gene expression, particularly at the transcriptional level. Increasing evidence suggests however that σ(E) may indirectly participate in post-transcriptional regulation.

HLA-B27 and human β2-microglobulin affect the gut microbiota of transgenic rats.

The HLA-B27 gene is a major risk factor for clinical diseases including ankylosing spondylitis, acute anterior uveitis, reactive arthritis, and psoriatic arthritis, but its mechanism of risk enhancement is not completely understood. The gut microbiome has recently been shown to influence several HLA-linked diseases. However, the role of HLA-B27 in shaping the gut microbiome has not been previously investigated.

Tractable mammalian cell infections with protozoan-primed bacteria.

Many intracellular bacterial pathogens use freshwater protozoans as a natural reservoir for proliferation in the environment. Legionella pneumophila, the causative agent of Legionnaires' pneumonia, gains a pathogenic advantage over in vitro cultured bacteria when first harvested from protozoan cells prior to infection of mammalian macrophages. This suggests that important virulence factors may not be properly expressed in vitro.

Barrier protection capacity of flip-top pharmaceutical vials.

Study Objective: To test the sterility of medication vial tops after removal of the dust cover, and to survey anesthesia providers for their perceptions surrounding medication vials and sterility.

Design: Experimental design and survey instrument.

Setting: Ambulatory and hospital care setting.

Computational prediction of type III and IV secreted effectors in gram-negative bacteria.

In this review, we provide an overview of the methods employed in four recent studies that described novel methods for computational prediction of secreted effectors from type III and IV secretion systems in Gram-negative bacteria. We present the results of these studies in terms of performance at accurately predicting secreted effectors and similarities found between secretion signals that may reflect biologically relevant features for recognition. We discuss the Web-based tools for secreted effector prediction described in these studies and announce the availability of our tool, the SIEVE server (http://www.

The Legionella pneumophila IcmSW complex interacts with multiple Dot/Icm effectors to facilitate type IV translocation.

Many gram-negative pathogens use a type IV secretion system (T4SS) to deliver effector proteins into eukaryotic host cells. The fidelity of protein translocation depends on the efficient recognition of effector proteins by the T4SS. Legionella pneumophila delivers a large number of effector proteins into eukaryotic cells using the Dot/Icm T4SS.

Recognition and delivery of effector proteins into eukaryotic cells by bacterial secretion systems.

The direct transport of virulence proteins from bacterium to host has emerged as a common strategy employed by Gram-negative pathogens to establish infections. Specialized secretion systems function to facilitate this process. The delivery of 'effector' proteins by these secretion systems is currently confined to two functionally similar but mechanistically distinct pathways, termed type III and type IV secretion.

The Legionella IcmS-IcmW protein complex is important for Dot/Icm-mediated protein translocation.

The intracellular pathogen Legionella pneumophila can infect and replicate within macrophages of a human host. To establish infection, Legionella require the Dot/Icm secretion system to inject protein substrates directly into the host cell cytoplasm. The mechanism by which substrate proteins are engaged and translocated by the Dot/Icm system is not well understood.

A C-terminal translocation signal required for Dot/Icm-dependent delivery of the Legionella RalF protein to host cells.

The Legionella pneumophila Dot/Icm system is a type IV secretion apparatus that transfers bacterial proteins into eukaryotic host cells. The RalF protein is a substrate engaged and translocated into host cells by the Dot/Icm system. In this study, the mechanism of Dot/Icm-mediated translocation of RalF has been investigated.

Binding of SycH chaperone to YscM1 and YscM2 activates effector yop expression in Yersinia enterocolitica.

Yersinia enterocolitica transports YscM1 and YscM2 via the type III pathway, a mechanism that is required for the establishment of bacterial infections. Prior to host cell contact, YscM1 and YscM2 exert posttranscriptional regulation to inhibit expression of effector yop genes, which encode virulence factors that travel the type III pathway into the cytoplasm of macrophages. Relief from repression has been predicted to occur via the type III secretion of YscM1 and YscM2 into the extracellular medium, resulting in the depletion of regulatory molecules from the bacterial cytoplasm.

Yersinia enterocolitica type III secretion: yscM1 and yscM2 regulate yop gene expression by a posttranscriptional mechanism that targets the 5' untranslated region of yop mRNA.

Pathogenic Yersinia spp. secrete Yops (Yersinia outer proteins) via the type III pathway. The expression of yop genes is regulated in response to environmental cues, which results in a cascade of type III secretion reactions.