Campsurus violaceus (Ephemeroptera, Polymitarcyidae) in a subtropical reservoir: control factors and relationship with the macroinvertebrate community

Campsurus violaceus is a benthic species that play an important role in sediment bioturbation processes. We explored aspects of its basic biology and life-cycle in a subtropical lake (Laguna del Sauce, Uruguay). We elucidated the habitat preference of C. violaceus and evaluated if might foster a more diverse and abundant macroinvertebrate community. The population of C. violaceus showed univoltine behavior with nymphs all year around. The spatial distribution of Campsurus in the system was related with various sediment attributes, particularly granulometry. A clear positive relationship between abundance of C. violaceus and the associated macroinvertebrate community was found. This association could not be explained by the availability of basal resources, nor sediment preferences, but direct or indirect biotic interactions appeared to be importan

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