Deep dive into the chronic toxicity of tyre particle mixtures and their leachates.

This is the final version. Available from Elsevier via the DOI in this record. Data Availability: Data will be made available on request.Particles from the tread of vehicle tyres are a global pollutant, which are emitted into the environment at an approximate rate of 1.4 kg.year-1 for an average passenger-car. In this study, popular tyre brands were used to generate a tyre tread microparticle mixture. The chronic toxicity of both particles and chemical leachates were compared on a planktonic test species (Daphnia magna). Over 21 days of exposure, pristine tyre tread microparticles were more toxic (LC50 60 mg.L-1) than chemical lechates alone (LC50 542 mg.L-1). Microparticles and leachates showed distinct effects on reproduction and morphological development at environmentally relevant concentrations, with dose-dependent uptake of particles visible in the digestive tract. Chemical characterization of leachates revealed a metal predominance of zinc, titanium, and strontium. Of the numerous organic chemicals present, at least 54 were shared across all 5 tyre brands, with many classified to be very toxic. Our results provide a critically needed information on the toxicity of tyre tread particles and the associated chemicals that leach from them to inform future mitigation measures. We conclude that tyre particles are hazardous pollutants of particular concern that are close to or possibly above chronic environmental safety limits in some locations.Natural Environment Research Council (NERC

Gamma estimator of Jarzynski equality for recovering binding energies from noisy dynamic data sets

A fundamental problem in thermodynamics is the recovery of macroscopic equilibrated interaction energies from experimentally measured single-molecular interactions. The Jarzynski equality forms a theoretical basis in recovering the free energy difference between two states from exponentially averaged work performed to switch the states. In practice, the exponentially averaged work value is estimated as the mean of finite samples. Numerical simulations have shown that samples having thousands of measurements are not large enough for the mean to converge when the fluctuation of external work is above 4 kBT, which is easily observable in biomolecular interactions. We report the first example of a statistical gamma work distribution applied to single molecule pulling experiments. The Gibbs free energy of surface adsorption can be accurately evaluated even for a small sample size. The values obtained are comparable to those derived from multi-parametric surface plasmon resonance measurements and molecular dynamics simulations

NEURAL NETWORKS AS AN ALTERNATIVE METHOD FOR PREDICTING BACTERIAL GROWTH RATE FROM THE BEGINNING OF A GROWTH CURVE

International audienc

Accuracy of microbial growth predictions with square root and polynomial models

International audienc

An accurate diffusion method for determining bacterial sensitivity to antibiotics

International audienc

An economic approach to the MIC.

International audienceThe determination of the Inhibitory Concentration in Diffusion (ICD) is proposed as an alternative to the agar dilution Minimal Inhibitory Concentration (MIC) that is time-consuming and cumbersome for routine use. Based on the technique of the disk diffusion test, it consists in calculating a continuous variable, the ICD, corresponding to the antibiotic concentration in the agar at the edge of the inhibition zone. Six antibiotics were tested (ampicillin, cefotaxime, erythromycin, gentamicin, nalidixic acid and rifampicin) each against 17 to 51 strains of enterobacteria, Staphylococcus aureus and Enterococcus spp. and six other antibiotics (cefsulodin, ceftazidime, imipenem, piperacillin, ticarcillin and tobramycin), against 13 to 25 strains of Pseudomonas aeruginosa. A total of 284 antibiotic-strain combinations were tested. Three different antibiotic charges were obtained for each antibiotic by cutting commercial disks in two and four equal pieces. The ICD was calculated for each strain from the size of inhibition zones around a full disk, a half and a quarter of a disk. Concurrently, the MIC was performed, using a conventional agar dilution method. There was a good correlation between the two methods and reproducibility for the ICD proved to be correct. This reliable technique is very efficient both in terms of laboratory time and cost of materials and could be proposed for widespread use in clinical laboratories

Modeling the Lag Time of Listeria monocytogenes from Viable Count Enumeration and Optical Density Data

The following two factors significantly influence estimates of the maximum specific growth rate (μ(max)) and the lag-phase duration (λ): (i) the technique used to monitor bacterial growth and (ii) the model fitted to estimate parameters. In this study, nine strains of Listeria monocytogenes were monitored simultaneously by optical density (OD) analysis and by viable count enumeration (VCE) analysis. Four usual growth models were fitted to our data, and estimates of growth parameters were compared from one model to another and from one monitoring technique to another. Our results show that growth parameter estimates depended on the model used to fit data, whereas there were no systematic variations in the estimates of μ(max) and λ when the estimates were based on OD data instead of VCE data. By studying the evolution of OD and VCE simultaneously, we found that while log OD/VCE remained constant for some of our experiments, a visible linear increase occurred during the lag phase for other experiments. We developed a global model that fits both OD and VCE data. This model enabled us to detect for some of our strains an increase in OD during the lag phase. If not taken into account, this phenomenon may lead to an underestimate of λ

Application of a temperature-dependent von Bertalanffy growth model to bullhead Cottus gobio

International audienc