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.

光密度 (OD) 被广泛用于估计液体培养中的细胞密度，但无法在没有标准化校准协议的仪器之间进行比较，并且很难与实际细胞计数相关联。我们通过一项实验室间研究解决了这个问题，该研究比较了 244 个实验室的三种简单、低成本且易于访问的 OD 校准方案，这些方案适用于八种表达本构型 GFP 的大肠杆菌菌株. 根据我们的结果，我们建议使用二氧化硅微球的连续稀释将 OD 校准到估计的细胞计数，这产生高度精确的校准（95.5% 的残留量 <1.2 倍），易于评估质量控制，还评估仪器有效线性范围，并且可以与荧光校准结合以获得每个细胞的等效荧光素分子 (MEFL) 单位，允许与流式细胞术测量进行直接比较和数据融合：在我们的研究中，每个细胞的荧光测量显示板之间的平均差异仅为 1.07 倍读取器和流式细胞术数据。