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

PEARLS (Perspectives on Equity Advancement: Research and Learning Symposium), a Case Report in Promoting DEI in a Medical School Setting

PEARLS (Perspectives on Equity Advancement: Research and Learning Symposium) was a student-led, faculty-mentored, year-long initiative culminating in a symposium with three components: (1) “Change Agents”, where faculty leaders presented their research and advances in DEI and the impact on the community; (2) The “15% Better” initiative, which promoted individual commitments to improving DEI in the Frank H. Netter School of Medicine at Quinnipiac University through reflection on a monthly prompt and review of selected educational resources; and (3) “Grand Rounds Pitches’’ where student-designed scholarly DEI initiatives received competitive seed grants alongside a mentorship team that help support their project to completion. The 2022 post-event survey (RR 58%) showed that 100% of respondents felt inspired to engage more deeply in DEI after seeing the faculty’s work, felt committed to at least one action that furthers their learning or promotes DEI broadly, and were better able to describe student-led DEI projects. In total, 94% of respondents felt more connected to faculty and students advancing DEI in the school of medicine community and 91% felt a greater sense of belonging. The 15% Better initiative strengthened the belief that small individual DEI commitments can result in substantial positive changes for 73%, while 27% already believed this. In total, 61% were more likely to engage in DEI efforts this year and 36% already planned to engage. Qualitative data highlighted themes of inspiration, positive impact, and actionable change. PEARLS stands as an easily reproducible way for higher education institutions to engage their community in DEI strategies through its foundational elements of promoting belonging, fostering inspiration, and encouraging commitment to action