MICA Legionella, an innovative and rapid method for enumeration of Legionella pneumophila in French sanitary water.

A new innovative method, MICA Legionella, allows for the automatic enumeration of Legionella pneumophila in domestic water samples in 2 days, with a detection limit of 2 CFU per test portion. Here we show that it gives equivalent results to those obtained by the French standard method NF T90-431 in 7 to 15 days.

Validation of MICA Legionella for Enumeration of Legionella pneumophila in Sanitary Waters and Cooling Tower Waters: AOAC Performance Tested MethodSM 032201.

Background: Frequent testing for Legionella concentration in water is required by most health risk monitoring organizations worldwide. Domestic hot water and cooling tower water networks must be regularly controlled to prevent Legionnaires' disease, a potentially deadly lung infection. MICA Legionella is the fastest culture-based detection method for all serogroups of Legionella pneumophila, with automatic enumeration in 48 h and no need for confirmation.

A passive physical model for DnaK chaperoning.

Almost all living organisms use protein chaperones with a view to preventing proteins from misfolding or aggregation either spontaneously or during cellular stress. This work uses a reaction-diffusion stochastic model to describe the dynamic localization of the Hsp70 chaperone DnaK in Escherichia coli cells during transient proteotoxic collapse characterized by the accumulation of insoluble proteins. In the model, misfolded ('abnormal') proteins are produced during alcoholic stress and have the propensity to aggregate with a polymerization-like kinetics.

Hydrogen Peroxide Induced Cell Death: The Major Defences Relative Roles and Consequences in E. coli.

We recently developed a mathematical model for predicting reactive oxygen species (ROS) concentration and macromolecules oxidation in vivo. We constructed such a model using Escherichia coli as a model organism and a set of ordinary differential equations. In order to evaluate the major defences relative roles against hydrogen peroxide (H2 O2), we investigated the relative contributions of the various reactions to the dynamic system and searched for approximate analytical solutions for the explicit expression of changes in H2 O2 internal or external concentrations.

Hydrogen peroxide induced cell death: One or two modes of action?

Imlay and Linn show that exposure of logarithmically growing Escherichia coli to hydrogen peroxide (H2O2) leads to two kinetically distinguishable modes of cell killing. Mode one killing is pronounced near 1 mM concentration of H2O2 and is caused by DNA damage, whereas mode-two killing requires higher concentration ([Formula: see text]). The second mode seems to be essentially due to damage to all macromolecules.

Rapid and Specific Enrichment of Culturable Gram Negative Bacteria Using Non-Lethal Copper-Free Click Chemistry Coupled with Magnetic Beads Separation.

Currently, identification of pathogenic bacteria present at very low concentration requires a preliminary culture-based enrichment step. Many research efforts focus on the possibility to shorten this pre-enrichment step which is needed to reach the minimal number of cells that allows efficient identification. Rapid microbiological controls are a real public health issue and are required in food processing, water quality assessment or clinical pathology.

Identification of living Legionella pneumophila using species-specific metabolic lipopolysaccharide labeling.

Legionella pneumophila is a pathogenic bacterium involved in regular outbreaks characterized by a relatively high fatality rate and an important societal impact. Frequent monitoring of the presence of this bacterium in environmental water samples is necessary to prevent these epidemic events, but the traditional culture-based detection and identification method requires up to 10 days. Reported herein is a method allowing identification of Legionella pneumophila by metabolic lipopolysaccharide labeling which targets, for the first time, a precursor to monosaccharides that are specifically present within the O-antigen of the bacterium.

Characterization and resuscitation of 'non-culturable' cells of Legionella pneumophila.

Background: Legionella pneumophila is a waterborne pathogen responsible for Legionnaires' disease, an infection which can lead to potentially fatal pneumonia. After disinfection, L. pneumophila has been detected, like many other bacteria, in a "viable but non culturable" state (VBNC).

Single-cell analysis of cell viability after a biocide treatment unveils an absence of positive correlation between two commonly used viability markers.

Discrimination among viable/active or dead/inactive cells in a microbial community is a vital question to address issues on ecological microbiology or microbiological quality control. It is commonly assumed that metabolically active cells (ChemchromeV6 [CV6] procedure) correspond to viable cells (direct viable count procedure [DVC]), although this assumption has never been demonstrated and is therefore a matter of debate. Indeed, simultaneous determination of cell viability and metabolic activity has never been performed on the same cells.

Survival of extremely and moderately halophilic isolates of Tunisian solar salterns after UV-B or oxidative stress.

Adaptation to a solar saltern environment requires mechanisms providing tolerance not only to salinity but also to UV radiation (UVR) and to reactive oxygen species (ROS). We cultivated prokaryote halophiles from two different salinity ponds: the concentrator M1 pond (240 g·L(-1) NaCl) and the crystallizer TS pond (380 g·L(-1) NaCl). We then estimated UV-B and hydrogen peroxide resistance according to the optimal salt concentration for growth of the isolates.

Characterization of Halorubrum sfaxense sp. nov., a New Halophilic Archaeon Isolated from the Solar Saltern of Sfax in Tunisia.

An extremely halophilic archaeon, strain ETD6, was isolated from a marine solar saltern in Sfax, Tunisia. Analysis of the 16S rRNA gene sequence showed that the isolate was phylogenetically related to species of the genus Halorubrum among the family Halobacteriaceae, with a close relationship to Hrr. xinjiangense (99.

Toxicity of carbon dioxide: a review.

The toxicity of carbon dioxide has been established for close to a century. A number of animal experiments have explored both acute and long-term toxicity with respect to the lungs, the cardiovascular system, and the bladder, showing inflammatory and possible carcinogenic effects. Carbon dioxide also induces multiple fetal malformations and probably reduces fertility in animals.

Characterization of heterotrophic prokaryote subgroups in the Sfax coastal solar salterns by combining flow cytometry cell sorting and phylogenetic analysis.

Here, we combined flow cytometry (FCM) and phylogenetic analyses after cell sorting to characterize the dominant groups of the prokaryotic assemblages inhabiting two ponds of increasing salinity: a crystallizer pond (TS) with a salinity of 390 g/L, and the non-crystallizer pond (M1) with a salinity of 200 g/L retrieved from the solar saltern of Sfax in Tunisia. As expected, FCM analysis enabled the resolution of high nucleic acid content (HNA) and low nucleic acid content (LNA) prokaryotes. Next, we performed a taxonomic analysis of the bacterial and archaeal communities comprising the two most populated clusters by phylogenetic analyses of 16S rRNA gene clone library.

CO2 exacerbates oxygen toxicity.

Reactive oxygen species (ROS) are harmful because they can oxidize biological macromolecules. We show here that atmospheric CO(2) (concentration range studied: 40-1,000 p.p.

Staphylococcus aureus ClpC is involved in protection of carbon-metabolizing enzymes from carbonylation during stationary growth phase.

The ability of Staphylococcus aureus to adapt to various conditions of stress is the result of a complex regulatory response. Among them, ClpC, belonging to the Hsp100/Clp ATPase family, seems to play an important role. For instance, we previously demonstrated that a functional clpC deletion resulted in enhanced survival in the late stationary phase (death phase period) compared to the parental S.

Watching intracellular lipolysis in mycobacteria using time lapse fluorescence microscopy.

The fact that Mycobacterium tuberculosis mobilizes lipid bodies (LB) located in the cytosol during infection process has been proposed for decades. However, the mechanisms and dynamics of mobilization of these lipid droplets within mycobacteria are still not completely characterized. Evidence in favour of this characterization was obtained here using a combined fluorescent microscopy and computational image processing approach.

Rules governing selective protein carbonylation.

Background: Carbonyl derivatives are mainly formed by direct metal-catalysed oxidation (MCO) attacks on the amino-acid side chains of proline, arginine, lysine and threonine residues. For reasons unknown, only some proteins are prone to carbonylation.

Methodology/principal Findings: we used mass spectrometry analysis to identify carbonylated sites in: BSA that had undergone in vitro MCO, and 23 carbonylated proteins in Escherichia coli.

A microscope automated fluidic system to study bacterial processes in real time.

Most time lapse microscopy experiments studying bacterial processes ie growth, progression through the cell cycle and motility have been performed on thin nutrient agar pads. An important limitation of this approach is that dynamic perturbations of the experimental conditions cannot be easily performed. In eukaryotic cell biology, fluidic approaches have been largely used to study the impact of rapid environmental perturbations on live cells and in real time.

Respective roles of culturable and viable-but-nonculturable cells in the heterogeneity of Salmonella enterica serovar typhimurium invasiveness.

The existence of Salmonella enterica serovar Typhimurium viable-but-nonculturable (VBNC) cells is a public health concern since they could constitute unrecognized sources of infection if they retain their pathogenicity. To date, many studies have addressed the ability of S. Typhimurium VBNC cells to remain infectious, but their conclusions are conflicting.

Carbonylated proteins are detectable only in a degradation-resistant aggregate state in Escherichia coli.

Carbonylation is currently used as a marker for irreversible protein oxidative damage. Several studies indicate that carbonylated proteins are more prone to degradation than their nonoxidized counterparts. In this study, we observed that in Escherichia coli, more than 95% of the total carbonyl content consisted of insoluble protein and most were cytosolic proteins.

Protein aggregates: an aging factor involved in cell death.

In a previous study, we demonstrated the presence of protein aggregates in an exponentially grown Escherichia coli culture. In light of these observations, protein aggregates could be considered damage to cells that is able to pass from one generation to the next. Based on the assumption that the amount of aggregate protein could represent an aging factor, we monitored this amount in a bacterial culture during senescence.

Existence of abnormal protein aggregates in healthy Escherichia coli cells.

Protein aggregation is a phenomenon observed in all organisms and has often been linked with cell disorders. In addition, several groups have reported a virtual absence of protein aggregates in healthy cells. In contrast to previous studies and the expected outcome, we observed aggregated proteins in aerobic exponentially growing and "healthy" Escherichia coli cells.

TiO2 photocatalysis causes DNA damage via fenton reaction-generated hydroxyl radicals during the recovery period.

Here, we show that resistance of Escherichia coli to TiO2 photocatalysis involves defenses against reactive oxygen species. Results support the idea that TiO2 photocatalysis generates damage which later becomes deleterious during recovery. We found this to be partly due to DNA attack via hydroxyl radicals generated by the Fenton reaction during recovery.

Induction of a global stress response during the first step of Escherichia coli plate growth.

We have investigated the first events that occur when exponentially grown cells are transferred from a liquid medium (Luria-Bertani [LB]) to a solid medium (LB agar [LBA]). We observed an initial lag phase of 180 min for the wild type MG1655 without any apparent growth. This lack of growth was independent of the bacterial physiological state (either the stationary or the exponential phase), the solid medium composition, or the number of cells on the plate, but it was dependent on the bacterial genotype.