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Halide assays are important for the study of enzymatic dehalogenation, a topic of great industrial and scientific importance. Here we describe the development of a very sensitive halide assay that can detect less than a picomole of bromide ions, making it very useful for quantifying enzymatic dehalogenation products. Halides are oxidised under mild conditions using the vanadium‐dependent chloroperoxidase from Curvularia inaequalis, forming hypohalous acids that are detected using aminophenyl fluorescein. The assay is up to three orders of magnitude more sensitive than currently available alternatives, with detection limits of 20 nM for bromide and 1 μM for chloride and iodide. We demonstrate that the assay can be used to determine specific activities of dehalogenases and validate this by comparison to a well‐established GC‐MS method. This new assay will facilitate the identification and characterisation of novel dehalogenases and may also be of interest to those studying other halide‐producing enzymes., How sensitive! A simple, safe, and very sensitive assay for enzymatic dehalogenation is presented. The halides produced by dehalogenases are generally very unreactive and thus hard to detect. We use hydrogen peroxide and a haloperoxidase to activate halides to hypohalous acids, which are easily detected using the sensitive fluorogenic probe aminophenyl fluorescein.

Monitoring enzymatic activities at pH ranges compatible with their physiological optimum using fluorescent assays is important for high-throughput screening and engineering of novel biocatalysts as...

A label-free immunosensor for rapid detection of Salmonella Typhimurium based on electrochemical impedance spectroscopy was developed. Specific antibody was immobilized to a screen-printed electrode via cysteamine monolayer activated with glutaraldehyde and the impedance was measured between two gold electrodes. Different procedures for sample treatment (combinations of heat and sonication) were tested and their impact on the assay performance was compared. Atomic force microscopy was used to study the effect of the treatment on the cell shape and to confirm the specific binding of Salmonella to the sensing surface. The immunosensor allowed detection of 1×10^3 CFU·mL-1 in 20 min with negligible interference from other bacteria. Wide linear response was obtained in the range between 10^3 CFU·mL-1 and 10^8 CFU·mL-1. The successful detection of Salmonella in spiked milk demonstrates the suitability of sensor for the analysis of real samples.

Airborne microorganisms are a major cause of respiratory diseases. Detection of pathogenic bacteria in the form of bioaerosols is required not only in peacetime but also in the threat of biological attacks. The label-free and direct detection of aerosolized biological agents is presented here. A desktop bioaerosol chamber for safe work with aerosolized microbial cells was constructed, and its functionality was tested. The model organisms (Escherichia coli) were disseminated using an aerosol generator in the chamber filled with either common laboratory indoor air or sterile air. The particles from the generated aerosol were collected using the cyclone SASS 2300, suspended in buffer and then analyzed using the piezoelectric immunosensor modified with specific capture antibodies. The frequency shifts indicated presence of the model biological agent with limit of detection of 1.45 × 10(4) CFU·L(-1) of air. The total time from sample collection to detection was 16 min. The system was fully automated and controlled remotely through a local network.