Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Whole-cell fluorescent bacterial bioreporter for arsenic detection in water

Microbial whole-cell bioreporters have been developed for environmental monitoring of arsenic contamination. Despite the great interest in bacterial bioreporters for arsenite detection, relatively few studies reported their response to arsenate levels. In this study, green fluorescent protein-based whole-cell Escherichia coli bioreporter was constructed for the measurement of both bioavailable arsenite and arsenate in water. The developed bacterial bioreporter has much higher sensitivity toward arsenate in inorganic phosphate-limiting medium compared to minimal medium. Both arsenite and arsenate were detected at 10 mu g/l within 2-h induction time period. Furthermore, the bioreporter was able to detect and estimate arsenic levels in groundwater sample. The results demonstrate that the constructed bacterial arsenic bioreporter is applicable in determining the concentrations of the most abundant two ionic forms of arsenic as opposed to analytical methods which gives total content of arsenic. Thus, a comparison of bioavailability of arsenic and its form with its total content would give an insight about the risk of toxicity and also planning of removal processes

Comparison of efficiency of Kinesio (R) taping and electrical stimulation in patients with patellofemoral pain syndrome

Objective: The aim of this study was to compare the efficiency of Kinesio (R) taping and electrical stimulation in the treatment of patellofemoral pain syndrome

Quiz case of the month - Fibrolipomatous hamartoma of the median nerve.

WOS: 000086150100031PubMed ID: 1075701