RT Journal Article SR Electronic T1 General calibration of microbial growth in microplate readers JF bioRxiv FD Cold Spring Harbor Laboratory SP 061861 DO 10.1101/061861 A1 Keiran Stevenson A1 Alexander F. McVey A1 Ivan B.N. Clark A1 Peter S. Swain A1 Teuta Pilizota YR 2016 UL http://biorxiv.org/content/early/2016/07/04/061861.abstract AB Optical density (OD) measurements of microbial growth are one of the most common techniques used in microbiology, with applications ranging from antibiotic efficacy studies, studies of growth under different nutritional or stress environments, to studies of different mutant strains, including those harbouring synthetic circuits. OD measurements are performed under the assumption that the OD value obtained is proportional to the cell number, i.e. the concentration of the sample. However, the assumption holds true in a limited range of conditions and calibration techniques that determine that range are currently missing. Here we present a set of calibration procedures and considerations that are necessary to successfully estimate the cell concentration from OD measurements.