Competence induction of homologous recombination genes protects pneumococcal cells from genotoxic stress.

Homologous recombination (HR) is a universally conserved mechanism of DNA strand exchange between homologous sequences, driven in bacteria by the RecA recombinase. HR is key for the maintenance of bacterial genomes via replication fork restart and DNA repair, as well as for their plasticity via the widespread mechanism of natural transformation. Transformation involves the capture and internalization of exogenous DNA in the form of single strands, followed by HR-mediated chromosomal integration.

Mechanistic and functional aspects of the Ruminococcin C sactipeptide isoforms.

In a scenario where the discovery of new molecules to fight antibiotic resistance is a public health concern, ribosomally synthesized and post-translationally modified peptides constitute a promising alternative. In this context, the Gram-positive human gut symbiont E1 produces five sactipeptides, Ruminococcins C1 to C5 (RumC1-C5), co-expressed with two radical SAM maturases. RumC1 has been shown to be effective against various multidrug resistant Gram-positives clinical isolates.

Natural Genetic Transformation: A Direct Route to Easy Insertion of Chimeric Genes into the Pneumococcal Chromosome.

The ability of Streptococcus pneumoniae (the pneumococcus) to transform is particularly convenient for genome engineering. Several protocols relying on sequential positive and negative selection strategies have been described to create directed markerless modifications, including deletions, insertions, or point mutations. Transformation with DNA fragments carrying long flanking homology sequences is also used to generate mutations without selection but it requires high transformability.

Dynamic Modeling of Competence Provides Regulatory Mechanistic Insights Into Its Tight Temporal Regulation.

In the human pathogen , the gene regulatory circuit leading to the transient state of competence for natural transformation is based on production of an auto-inducer that activates a positive feedback loop. About 100 genes are activated in two successive waves linked by a central alternative sigma factor ComX. This mechanism appears to be fundamental to the biological fitness of .

Bacterial RadA is a DnaB-type helicase interacting with RecA to promote bidirectional D-loop extension.

Homologous recombination (HR) is a central process of genome biology driven by a conserved recombinase, which catalyses the pairing of single-stranded DNA (ssDNA) with double-stranded DNA to generate a D-loop intermediate. Bacterial RadA is a conserved HR effector acting with RecA recombinase to promote ssDNA integration. The mechanism of this RadA-mediated assistance to RecA is unknown.

The SWI/SNF Protein PBRM1 Restrains VHL-Loss-Driven Clear Cell Renal Cell Carcinoma.

PBRM1 is the second most commonly mutated gene after VHL in clear cell renal cell carcinoma (ccRCC). However, the biological consequences of PBRM1 mutations for kidney tumorigenesis are unknown. Here, we find that kidney-specific deletion of Vhl and Pbrm1, but not either gene alone, results in bilateral, multifocal, transplantable clear cell kidney cancers.

Pneumococcal Competence Coordination Relies on a Cell-Contact Sensing Mechanism.

Bacteria have evolved various inducible genetic programs to face many types of stress that challenge their growth and survival. Competence is one such program. It enables genetic transformation, a major horizontal gene transfer process.

Direct involvement of DprA, the transformation-dedicated RecA loader, in the shut-off of pneumococcal competence.

Natural bacterial transformation is a genetically programmed process allowing genotype alterations that involves the internalization of DNA and its chromosomal integration catalyzed by the universal recombinase RecA, assisted by its transformation-dedicated loader, DNA processing protein A (DprA). In Streptococcus pneumoniae, the ability to internalize DNA, known as competence, is transient, developing suddenly and stopping as quickly. Competence is induced by the comC-encoded peptide, competence stimulating peptide (CSP), via a classic two-component regulatory system ComDE.

Metabolic adaptation to a high-fat diet is associated with a change in the gut microbiota.

Objective: The gut microbiota, which is considered a causal factor in metabolic diseases as shown best in animals, is under the dual influence of the host genome and nutritional environment. This study investigated whether the gut microbiota per se, aside from changes in genetic background and diet, could sign different metabolic phenotypes in mice.

Methods: The unique animal model of metabolic adaptation was used, whereby C57Bl/6 male mice fed a high-fat carbohydrate-free diet (HFD) became either diabetic (HFD diabetic, HFD-D) or resisted diabetes (HFD diabetes-resistant, HFD-DR).

Intestinal mucosal adherence and translocation of commensal bacteria at the early onset of type 2 diabetes: molecular mechanisms and probiotic treatment.

A fat-enriched diet modifies intestinal microbiota and initiates a low-grade inflammation, insulin resistance and type-2 diabetes. Here, we demonstrate that before the onset of diabetes, after only one week of a high-fat diet (HFD), live commensal intestinal bacteria are present in large numbers in the adipose tissue and the blood where they can induce inflammation. This translocation is prevented in mice lacking the microbial pattern recognition receptors Nod1 or CD14, but overtly increased in Myd88 knockout and ob/ob mouse.

Neuropilin-1 is upregulated in hepatocellular carcinoma and contributes to tumour growth and vascular remodelling.

Background & Aims: Neuropilin-1 (NRP1) is a transmembrane co-receptor for semaphorins and heparin-binding pro-angiogenic cytokines, principally members of the vascular endothelial growth factor family. Recent studies revealed an important role of NRP1 in angiogenesis and malignant progression of many cancers. The role of NRP1 in the development of hepatocellular carcinoma (HCC) is not completely understood.

Effects of ionic strength on bacteriophage MS2 behavior and their implications for the assessment of virus retention by ultrafiltration membranes.

Bacteriophage MS2 is widely used as a surrogate to estimate pathogenic virus elimination by membrane filtration processes used in water treatment. Given that this water technology may be conducted with different types of waters, we focused on investigating the effects of ionic strength on MS2 behavior. For this, MS2 was analyzed while suspended in solutions of various ionic strengths, first in a batch experiment and second during membrane ultrafiltration, and quantified using (i) quantitative reverse transcriptase PCR (qRT-PCR), which detects the total number of viral genomes, (ii) qRT-PCR without the RNA extraction step, which reflects only particles with a broken capsid (free RNA), and (iii) the PFU method, which detects only infectious viruses.

Small interfering RNAs induce target-independent inhibition of tumor growth and vasculature remodeling in a mouse model of hepatocellular carcinoma.

RNA interference mediated by small interfering RNAs (siRNAs) has emerged as a potential therapeutic approach to treat various diseases, including cancer. Recent studies with several animal models of posttraumatic revascularization demonstrated that synthetic siRNAs may produce therapeutic effects in a target-independent manner through the stimulation of the toll-like receptor-3 (TLR3)/interferon pathway and suppression of angiogenesis. To analyze the impact of siRNAs on tumor angiogenesis, we injected transgenic mice developing hepatocellular carcinoma (HCC) with either control siRNAs or siRNA targeting neuropilin-1.

Catalysis of the electrochemical reduction of oxygen by bacteria isolated from electro-active biofilms formed in seawater.

Biofilms formed in aerobic seawater on stainless steel are known to be efficient catalysts of the electrochemical reduction of oxygen. Based on their genomic analysis, seven bacterial isolates were selected and a cyclic voltammetry (CV) procedure was implemented to check their electrocatalytic activity towards oxygen reduction. All isolates exhibited close catalytic characteristics.

Growth inhibition of adherent Pseudomonas aeruginosa by an N-butanoyl-L-homoserine lactone analog.

The discovery of quorum sensing (QS) communication systems regulating bacterial virulence has afforded a novel opportunity for controlling infectious bacteria by interfering with QS. Pseudomonas aeruginosa is an example of an opportunistic human pathogen for which N-acyl homoserine lactone (AHL)-related compounds have been described as potent inhibitors of biofilm formation and virulence factors, given their similarity to the natural QS autoinducers (AHLs). Our purpose was to design potent analogs of N-butanoyl-L-homoserine lactone (C4-HSL) and to screen them for biological activity.

Cross-talk between the VEGF-A and HGF signalling pathways in endothelial cells.

Background Information: Endothelial cells play a major role in angiogenesis, the process by which new blood vessels arise from a pre-existing vascular bed. VEGF-A (vascular endothelial growth factor-A) is a key regulator of angiogenesis during both development and in adults. HGF (hepatocyte growth factor) is a pleiotropic cytokine that may promote VEGF-A-driven angiogenesis, although the signalling mechanisms underlying this co-operation are not completely understood.

Neuropilin-1 and neuropilin-2 act as coreceptors, potentiating proangiogenic activity.

Neuropilin-1 and -2 (NRP1 and NRP2) are the transmembrane glycoproteins interacting with 2 types of ligands: class III semaphorins and several members of the VEGF family, the main regulators of blood and lymphatic vessel growth. We show here that both NRP1 and NRP2 can also bind hepatocyte growth factor (HGF). HGF is a pleiotropic cytokine and potent proangiogenic molecule that acts on its target cells by binding to the c-met receptor.

Transformation of Streptococcus pneumoniae relies on DprA- and RecA-dependent protection of incoming DNA single strands.

Seventy-five years after the discovery of transformation with Streptococcus pneumoniae, it is remarkable how little we know of the proteins that interact with incoming single strands in the early processing of transforming DNA. In this work, we used as donor DNA in transformation a radioactively labelled homologous fragment to examine the fate of the single-stranded (ssDNA) products of uptake in cells mutant for DprA or RecA, two proteins essential for transformation. Fifteen minutes after uptake, the labelling of specific chromosomal restriction fragments that demonstrated homologous integration in the wild type was not detected in dprA or recA cells, indicating that in the mutants incoming ssDNA could not be processed into recombinants.

Uptake of transforming DNA in Gram-positive bacteria: a view from Streptococcus pneumoniae.

In a working model for the uptake of transforming DNA based on evidence taken from both Bacillus subtilis and Streptococcus pneumoniae, the ComG proteins are proposed to form a structure that provides access for DNA to the ComEA receptor through the peptidoglycan. DNA would then be delivered to the ComEC-ComFA transport complex. A DNA strand would be degraded by a nuclease, while its complement is pulled into the cell by ComFA through an aqueous pore formed by ComEC.

Identification of a protein that inactivates the competence-stimulating peptide of Streptococcus pneumoniae.

Competence for genetic transformation of Streptococcus pneumoniae is a transient physiological property inducible by a competence-stimulating peptide (CSP). A 68-kDa CSP-inactivating protein was previously obtained following lithium chloride (LiCl) extraction. By the same protocol, a CSP-inactivating protein was purified and identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry as an endopeptidase, PepO.