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Current Opinion in Microbiology

Qing Chen, Scott Stibitz
The BvgAS two-component system of Bordetella pertussis directly activates the expression of a large number of virulence genes in an environmentally responsive manner. The Bvg+ mode also promotes the expression of the phosphodiesterase BvgR, which turns off the expression of another set of genes, the vrgs, by reducing levels of c-di-GMP. Increased levels of c-di-GMP in the Bvg- mode are required, together with the phosphorylated response regulator protein RisA∼P, to activate vrg expression. Phosphorylation of RisA requires RisK, a non-co-operonic sensor kinase, but not its co-operonic sensor kinase RisS which is truncated in B...
March 11, 2019: Current Opinion in Microbiology
Lucy Foulston
Natural products are a rich source of bioactive compounds that have been used successfully in the areas of human health from infectious disease to cancer; however, traditional fermentation-based screening has provided diminishing returns over the last 20-30 years. Solutions to the unmet need of resistant bacterial infection are critically required. Technological advances in high-throughput genomic sequencing, coupled with ever-decreasing cost, are now presenting a unique opportunity for the reinvigoration of natural product discovery...
February 15, 2019: Current Opinion in Microbiology
Kelly A Miller, Katharine F Tomberlin, Michelle Dziejman
Mounting evidence suggests that Type 3 Secretion Systems (T3SS) are widespread among Vibrio species, and are present in strains isolated from diverse sources such as human clinical infections, environmental reservoirs, and diseased marine life. Experiments evaluating Vibrio parahaemolyticus and Vibrio cholerae T3SS mediated virulence suggest that Vibrio T3SS pathogenicity islands have a tripartite composition. A conserved 'core' region encodes functions essential for colonization and disease in vivo, including modulation of innate immune signaling pathways and actin dynamics, whereas regions flanking core sequences are variable among strains and encode effector proteins performing a diverse array of activities...
January 31, 2019: Current Opinion in Microbiology
Inaya Hayek, Christian Berens, Anja Lührmann
Intracellular bacterial pathogens intimately interact with the infected host cell to prevent elimination and to ensure survival. One group of intracellular pathogens, including Coxiella burnetii, Legionella pneumophila, Brucella spp., Anaplasma phagocytophilum, and Ehrlichia chaffeensis, utilizes a type IV secretion system (T4SS) that injects effectors to modulate host cell signalling, vesicular trafficking, autophagy, cell death and transcription to ensure survival [1]. So far, little emphasis has been directed towards understanding how these bacteria manipulate host cell metabolism...
January 10, 2019: Current Opinion in Microbiology
Joshua M Lensmire, Neal D Hammer
Pathogens have evolved elegant mechanisms to acquire essential nutrients from host environments. Sulfur is a requirement for bacterial growth and inorganic and organic sulfur-containing metabolites are abundant within the host-pathogen interface. A growing body of evidence suggests that pathogens are capable of scavenging both types of sulfur sources to fulfill the nutritional requirement. While therapeutic strategies focusing on inhibiting inorganic sulfate assimilation and cysteine synthesis show promise in vitro, in vivo efficacy maybe limited due to the diversity of host-derived sulfur sources and the fact that most pathogens are capable of acquiring multiple sources of sulfur...
December 7, 2018: Current Opinion in Microbiology
Linda J Kenney
After uptake by epithelial cells or engulfment by macrophages, Salmonella resides in an acidic vacuole. Salmonella senses this acidic compartment through the action of the EnvZ/OmpR two-component regulatory system. OmpR, in turn, represses the cadC/BA system, preventing neutralization of the bacterial cytoplasm. New, single cell techniques now enable us to observe that in response to acid stress, the pH is low in bacterial cells and acidification is critical for infection. Instead of recovering from acid stress, Salmonella uses acid pH as a signal to drive pathogenesis...
December 4, 2018: Current Opinion in Microbiology
Pascal Mäser
No abstract text is available yet for this article.
December 2018: Current Opinion in Microbiology
Ralph A Dean, Thierry Rouxel
No abstract text is available yet for this article.
December 2018: Current Opinion in Microbiology
Matteo Rossi, Nicolas Fasel
In nature, humans infected with protozoan parasites can encounter viruses, which could alter their host immune response. The impact of viruses on human parasitic diseases remains largely unexplored due to the highly sterilized environment in experimental studies and the difficulty to draw a correlation between co-infection and pathology. Recent studies show that viral infections exacerbate pathology and promote dissemination of some Leishmania infections, based on a hyper-inflammatory reaction driven by type I interferons...
December 2018: Current Opinion in Microbiology
Lay-Sun Ma, Clément Pellegrin, Regine Kahmann
Pathogenic and symbiotic filamentous microbes secrete effectors which suppress host immune responses and promote a successful colonization. Pathogen effectors are engaged in the arms race with their hosts and because of this they are subject to intense evolutionary pressure. Effectors particularly prone to rapid evolution display repeat-containing domains which can easily expand or contract and accumulate point mutations without altering their original function. In this review we address the diversity of function in such repeat-containing effectors, focus on new findings and point out avenues for future work...
December 2018: Current Opinion in Microbiology
Qiang Cai, Baoye He, Karl-Heinz Kogel, Hailing Jin
In plants, small RNA (sRNA)-mediated RNA interference (RNAi) is critical for regulating host immunity against bacteria, fungi, oomycetes, viruses, and pests. Similarly, sRNAs from pathogens and pests also play an important role in modulating their virulence. Strikingly, recent evidence supports that some sRNAs can travel between interacting organisms and induce gene silencing in the counter party, a mechanism termed cross-kingdom RNAi. Exploiting this new knowledge, host-induced gene silencing (HIGS) by transgenic expression of pathogen gene-targeting double-stranded (ds)RNA has the potential to become an important disease-control method...
December 2018: Current Opinion in Microbiology
Christina Yang, Karen M Ottemann
The epithelial cell layer of the major organs of the mammalian gastrointestinal (GI) tract is extensively invaginated into thousands of gland and crypt structures. These are lined by distinct sets of epithelial cells and may comprise discrete niches. The host maximizes the distance between the epithelial cell layer and GI-inhabiting microbes to limit inflammation, and these strategies also likely keep bacteria out of the glands and crypts. We discuss here the specific host processes that have been shown to restrict bacterial presence in the glands and crypts, specifically the immune system, acid, mucin, oxygen, and reactive oxygen species...
November 28, 2018: Current Opinion in Microbiology
Vishal C Kalel, Pascal Mäser, Michael Sattler, Ralf Erdmann, Grzegorz M Popowicz
Glycosomes evolved as specialized system for glycolysis in trypanosomatids. These organelle rely on protein import to maintain function. A machinery of peroxin (PEX) proteins is responsible for recognition and transport of glycosomal proteins to the organelle. Disruption of PEX-based import system was expected to be a strategy against trypanosomatids. Recently, a proof of this hypothesis has been presented. Here, we review current information about trypanosomatids' glycosomal transport components as targets for new trypanocidal therapies...
November 24, 2018: Current Opinion in Microbiology
Victoria Korolik
Campylobacter jejuni is a ubiquitous gastrointestinal pathogen, transmitted to humans from birds and animals, where C. jejuni is part of normal intestinal flora. In C. jejuni, similar to other motile bacteria, chemotaxis pathway and the array of chemosensors sense and respond to external stimuli with unique precision and sensitivity and are considered to be critical for bacterial colonisation and pathogenicity. Disruption of any component of the signal transduction pathway consisting of receptor-CheA/CheW-CheY-flagella cascade, the signal adaptation system, and even a loss of a single chemosensory receptor, dramatically reduce the ability of C...
November 23, 2018: Current Opinion in Microbiology
Leou Ismael Banla, Nita H Salzman, Christopher J Kristich
Enterococci are colonizers of the mammalian gastrointestinal tract (GIT) and normally live in healthy association with their human host. However, enterococci are also major causes of healthcare-acquired infections, prompting the US Centers for Disease Control and Prevention to declare vancomycin-resistant enterococci (VRE) a serious threat to public health. Because of both intrinsic and acquired antibiotic resistance, enterococci proliferate in the GIT during antibiotic therapy, leading to dissemination and disease...
November 12, 2018: Current Opinion in Microbiology
Brittany R Ruhland, Michelle L Reniere
Listeria monocytogenes (Lm) is a Gram-positive bacterium that thrives in nature as a saprophyte and in the mammalian host as an intracellular pathogen. Both environments pose potential danger in the form of redox stress. In addition, endogenous reactive oxygen species (ROS) are continuously generated as by-products of aerobic metabolism. Redox stress from ROS can damage proteins, lipids, and DNA, making it highly advantageous for bacteria to evolve mechanisms to sense and detoxify ROS. This review focuses on the five redox-responsive regulators in Lm: OhrR (to sense organic hydroperoxides), PerR (peroxides), Rex (NAD+ /NADH homeostasis), SpxA1/2 (disulfide stress), and PrfA (redox stress during infection)...
November 6, 2018: Current Opinion in Microbiology
Joanne Wk Ku, Yunn-Hwen Gan
Glutathione is a low molecular weight thiol that is important for maintaining intracellular redox homeostasis. Some bacteria are able to import exogenous glutathione as a nutritional source and to counter oxidative stress. In cytosolic pathogens Burkholderia pseudomallei and Listeria monocytogenes, host glutathione regulates bacterial virulence. In B. pseudomallei, glutathione activates the membrane-bound histidine kinase sensor VirA that leads to activation of the Type VI Secretion System. In L. monocytogenes, host glutathione leads to the binding of bacterial glutathione to the master virulence regulator PrfA as an allosteric activator...
November 2, 2018: Current Opinion in Microbiology
Tomoko Kubori, Tomoe Kitao, Hiroki Nagai
Bacterial pathogens utilize eukaryotic cellular systems in various ways for their own benefits. To counteract host immune responses and survive in cells, bacteria modify host signaling pathways. For this aim, they have evolved virulence secretion systems. Bacteria-encoded effector proteins delivered via these secretion systems are the key players in bacterial pathogenesis. Ubiquitination is a post-translational modification that governs eukaryotic cellular systems. Recent studies have revealed that many bacterial effector proteins target the host ubiquitin system, often acting as ubiquitin-modulating enzymes such as ubiquitin ligases and deubiquitinases...
November 1, 2018: Current Opinion in Microbiology
Amit Tuli, Mahak Sharma
Pathogens have devised various strategies to alter the host endomembrane system towards building their replicative niche. This is aptly illustrated by Salmonella Typhimurium, whereby it remodels the host endolysosomal system to form a unique niche, also known as Salmonella-containing vacuole (SCV). Decades of research using in vitro cell-based infection studies have revealed intricate details of how Salmonella effectors target endocytic trafficking machinery of the host cell to acquire membrane and nutrients for bacterial replication...
November 1, 2018: Current Opinion in Microbiology
Usheer Kanjee, Gabriel W Rangel, Martha A Clark, Manoj T Duraisingh
Plasmodium vivax is uniquely restricted to invading reticulocytes, the youngest of red blood cells. Parasite invasion relies on the sequential deployment of multiple parasite invasion ligands. Correct targeting of the host reticulocyte is mediated by two families of invasion ligands: the reticulocyte binding proteins (RBPs) and erythrocyte binding proteins (EBPs). The Duffy receptor has long been established as a key determinant for P. vivax invasion. However, recently, the RBP protein PvRBP2b has been shown to bind to transferrin receptor, which is expressed on reticulocytes but lost on normocytes, implicating the ligand-receptor in the reticulocyte tropism of P...
October 23, 2018: Current Opinion in Microbiology
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