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

Sir Walter Ralegh

42 p.; 20 cm

‘Everything is said with a smile’: Homonegative speech acts in sport

The acceptance of gay males in sport is growing in various western countries. However, research also suggests that young males, including athletes, tend to engage in homonegative speech acts, often called microaggressions, that make it difficult for them to navigate practices of masculinity. We used solicited diaries or diary logs written by (non-)heterosexual young male team sport athletes (aged 16–25) to investigate how they experienced and heard expressions of homonegative and heteronormative microaggressive speech acts. We drew on Foucault’s notion of discourse, Butler’s conceptualization of performativity of heteronormativity and Sue’s work on microaggressions to examine how microaggressive speech acts by young male athletes reflect current sexual and gender cultural norms. The results revealed how homonegative speech acts were embedded in a gay aesthetic and abject femininity and used to endorse a desirable heteronormative masculinity. We concluded that homonegative microaggressive speech acts contribute to the preservation of discursive heteronormativity in sport despite growing acceptance of non-heterosexual male athletes