Rifampicin-resistant RpoB S522L Vibrio vulnificus exhibits disturbed stress response and hypervirulence traits.

Rifampicin resistance, which is genetically linked to mutations in the RNA polymerase β-subunit gene rpoB, has a global impact on bacterial transcription and cell physiology. Previously, we identified a substitution of serine 522 in RpoB (i.e.

Venom extraction method influences venom composition and potency in the giant house spider Eratigena atrica (C. L. Koch, 1843).

Extraction is the first step when investigating venom composition and function. In small invertebrates, widely used extraction methods include electrostimulation and venom gland extraction, however, the influence of these methods on composition and toxicology is poorly understood. Using the Giant House Spider Eratigena atrica as a model, we show that electrostimulation and venom gland removal extraction methods produce different protein profiles as assessed by Coomassie-stained SDS-PAGE and significantly different potencies in the cricket Acheta domesticus.

The stressosome is dispensable in nutrient-rich media.

The stressosome is a protein complex that senses environmental stresses and mediates the stress response in several Gram-positive bacteria through the activation of the alternative sigma factor SigB. The stressosome locus is found in 44 % of Gram-negative isolates. However, does not possess SigB.

Inhibition of bacterial biofilms by the snake venom proteome.

Snake venoms possess a range of pharmacological and toxicological activities. Here we evaluated the antibacterial and anti-biofilm activity against methicillin-susceptible and methicillin-resistant (MSSA and MRSA) of venoms from the Samar spitting cobra and the Puff adder Both venoms prevented biofilm production by pathogenic in a growth-independent manner, with the venom being most potent. Fractionation showed the active molecule to be heat-labile and >10 kDa in size.

Sponge-derived fatty acids inhibit biofilm formation of MRSA and MSSA by down-regulating biofilm-related genes specific to each pathogen.

Aim: A promising approach for the development of next-generation antimicrobials is to shift their target from causing bacterial death to inhibiting virulence. Marine sponges are an excellent potential source of bioactive anti-virulence molecules (AVM). We screened fractions prepared from 26 samples of Irish coastal sponges for anti-biofilm activity against clinically relevant pathogens.

characterisation of the stressosome: A complex involved in reshaping glucose metabolism and motility regulation, in nutrient- and iron-limited growth conditions.

Stressosomes are signal-sensing and integration hubs identified in many bacteria. At present, the role of the stressosome has only been investigated in Gram-positive bacteria. This work represents the first characterisation of the stressosome in a Gram-negative bacterium, .

The stressosome is required to transduce low pH signals leading to increased transcription of the amino acid-based acid tolerance mechanisms in .

Increasing proton concentration in the environment represents a potentially lethal stress for single-celled microorganisms. To survive in an acidifying environment, the foodborne pathogen quickly activates the alternative sigma factor B (σ), resulting in upregulation of the general stress response (GSR) regulon. Activation of σ is regulated by the stressosome, a multi-protein sensory complex involved in stress detection and signal transduction.

The Vibrio vulnificus stressosome is an oxygen-sensor involved in regulating iron metabolism.

Stressosomes are stress-sensing protein complexes widely conserved among bacteria. Although a role in the regulation of the general stress response is well documented in Gram-positive bacteria, the activating signals are still unclear, and little is known about the physiological function of stressosomes in the Gram-negative bacteria. Here we investigated the stressosome of the Gram-negative marine pathogen Vibrio vulnificus.

Evolution of Listeria monocytogenes Reveals Selective Pressure for Loss of SigB and AgrA Function at Different Incubation Temperatures.

The alternative sigma factor B (σ) contributes to the stress tolerance of the foodborne pathogen Listeria monocytogenes by upregulating the general stress response. We previously showed that σ loss-of-function mutations arise frequently in strains of L. monocytogenes and suggested that mild stresses might favor the selection of such mutations.

Validation of a random genomic library by selection of quinolone resistance in a heterologous host.

is a shellfish-borne pathogen that is a highly prevalent causative agent of inflammatory gastroenteritis in humans. Genomic libraries have proven useful for the identification of novel gene functions in many bacterial species. In this study we prepared a library containing 40 kb fragments of randomly sheared genomic DNA and introduced this into HB101 using a commercially available low copy cosmid system.

Acid stress signals are integrated into the σB-dependent general stress response pathway via the stressosome in the food-borne pathogen Listeria monocytogenes.

The general stress response (GSR) in Listeria monocytogenes plays a critical role in the survival of this pathogen in the host gastrointestinal tract. The GSR is regulated by the alternative sigma factor B (σB), whose role in protection against acid stress is well established. Here, we investigated the involvement of the stressosome, a sensory hub, in transducing low pH signals to induce the GSR.

Bis-Indole Alkaloids Isolated from the Sponge Disrupt Cell Membranes of MRSA.

Antimicrobial resistance (AMR) is a global health challenge with methicillin resistant (MRSA), a leading cause of nosocomial infection. In the search for novel antibiotics, marine sponges have become model organisms as they produce diverse bioactive compounds. We investigated and compared the antibacterial potential of 3 bis-indole alkaloids-bromodeoxytopsentin, bromotopsentin and spongotine A-isolated from the Northeastern Atlantic sponge .

Metagenomic identification, purification and characterisation of the Bifidobacterium adolescentis BgaC β-galactosidase.

Members of the human gut microbiota use glycoside hydrolase (GH) enzymes, such as β-galactosidases, to forage on host mucin glycans and dietary fibres. A human faecal metagenomic fosmid library was constructed and functionally screened to identify novel β-galactosidases. Out of the 16,000 clones screened, 30 β-galactosidase-positive clones were identified.

Synanthropic spiders, including the global invasive noble false widow Steatoda nobilis, are reservoirs for medically important and antibiotic resistant bacteria.

The false widow spider Steatoda nobilis is associated with bites which develop bacterial infections that are sometimes unresponsive to antibiotics. These could be secondary infections derived from opportunistic bacteria on the skin or infections directly vectored by the spider. In this study, we investigated whether it is plausible for S.

mutations conferring rifampicin-resistance affect growth, stress response and motility in .

Rifampicin is a broad-spectrum antibiotic that binds to the bacterial RNA polymerase (RNAP), compromising DNA transcription. Rifampicin resistance is common in several microorganisms and it is typically caused by point mutations in the gene encoding the β subunit of RNA polymerase, . Different mutations are responsible for various levels of rifampicin resistance and for a range of secondary effects.

Mild Stress Conditions during Laboratory Culture Promote the Proliferation of Mutations That Negatively Affect Sigma B Activity in Listeria monocytogenes.

In , the full details of how stress signals are integrated into the σ regulatory pathway are not yet available. To help shed light on this question, we investigated a collection of transposon mutants that were predicted to have compromised activity of the alternative sigma factor B (σ). These mutants were tested for acid tolerance, a trait that is known to be under σ regulation, and they were found to display increased acid sensitivity, similar to a mutant lacking σ (Δ).

Brominated Bisindole Alkaloids from the Celtic Sea Sponge .

As part of an ongoing program to identify new bioactive compounds from Irish marine bioresources, we selected the subtidal sponge for chemical study, as fractions of this species displayed interesting cytotoxic bioactivities and chemical profiles. The first chemical investigation of this marine species led to the discovery of two new bisindole alkaloids of the topsentin family, together with six other known indole alkaloids. Missing the usual central core featured by the representatives of these marine natural products, the new metabolites may represent key biosynthetic intermediates for other known bisindoles.

In vitro comparative cytotoxicity study of a novel biocidal iodo-thiocyanate complex.

Novel biocides, which avoid the induction of cross-resistance to antibiotics, are an urgent societal requirement. Here, we compared the cytotoxic and bactericidal effects of a new antimicrobial agent, the iodo-thiocyanate complex (ITC), with those of the common antiseptics, hydrogen peroxide (HO), povidone iodine (PVP-I) and Lugol's iodine (Lugol). The antimicrobials were co-incubated for 10 min with HeLa and Escherichia coli cells in the presence and absence of organic matter (Dulbecco's modified Eagle's medium, supplemented with 10% fetal bovine serum).

Manipulation of intestinal epithelial cell function by the cell contact-dependent type III secretion systems of Vibrio parahaemolyticus.

Vibrio parahaemolyticus elicits gastroenteritis by deploying Type III Secretion Systems (TTSS) to deliver effector proteins into epithelial cells of the human intestinal tract. The bacteria must adhere to the human cells to allow colonization and operation of the TTSS translocation apparatus bridging the bacterium and the host cell. This article first reviews recent advances in identifying the molecules responsible for intercellular adherence.

Translocation of Vibrio parahaemolyticus across an in vitro M cell model.

Consumption of Vibrio parahaemolyticus via contaminated shellfish results in inflammatory gastroenteritis characterised by severe diarrhoea, nausea and stomach cramps. This study investigated the translocation of V. parahaemolyticus across a Peyer's patch M cell-like Caco-2/Raji B co-culture model system, as M cells represent a primary site of infection for many pathogenic bacteria.

The Vibrio parahaemolyticus ToxRS regulator is required for stress tolerance and colonization in a novel orogastric streptomycin-induced adult murine model.

Vibrio parahaemolyticus, a marine bacterium, is the causative agent of gastroenteritis associated with the consumption of seafood. It contains a homologue of the toxRS operon that in V. cholerae is the key regulator of virulence gene expression.

The Vibrio parahaemolyticus Type III Secretion Systems manipulate host cell MAPK for critical steps in pathogenesis.

Background: Vibrio parahaemolyticus is a food-borne pathogen causing inflammation of the gastrointestinal epithelium. Pathogenic strains of this bacterium possess two Type III Secretion Systems (TTSS) that deliver effector proteins into host cells. In order to better understand human host cell responses to V.

Bordetella pertussis expresses a functional type III secretion system that subverts protective innate and adaptive immune responses.

Certain bacteria use a type III secretion system (TTSS) to deliver effector proteins that interfere with cell function into host cells. While transcription of genes encoding TTSS components has been demonstrated, studies to date have failed to identify TTSS effector proteins in Bordetella pertussis. Here we present the first evidence of a functionally active TTSS in B.