New Paper Published: Estimating microbial population data from optical density

BRI Director, DR. Barry Hall has just co-authored a new paper on Estimating microbial population data from optical density, with primary author Portia Mira and Pamela Yeh, published by PLOS. PLOS is a nonprofit, Open Access publisher empowering researchers to accelerate progress in science and medicine by leading a transformation in research communication.

Read the Article

“The spectrophotometer has been used for decades to measure the density of bacterial populations as the turbidity expressed as optical density–OD. However, the OD alone is an unreliable metric and is only proportionately accurate to cell titers to about an OD of 0.1. The relationship between OD and cell titer depends on the configuration of the spectrophotometer, the length of the light path through the culture, the size of the bacterial cells, and the cell culture density. We demonstrate the importance of plate reader calibration to identify the exact relationship between OD and cells/mL. We use four bacterial genera and two sizes of micro-titer plates (96-well and 384-well) to show that the cell/ml per unit OD depends heavily on the bacterial cell size and plate size. We applied our calibration curve to real growth curve data and conclude the cells/mL–rather than OD–is a metric that can be used to directly compare results across experiments, labs, instruments, and species.”

Dr. Hall’s work with the paper’s collaborators continues to refine how laboratories can determine microbial growth rates with greater accuracy through techniques such as careful calibration of your spectrophotometer.

Read the full article to walk through the materials and methods used, the results, and supporting graphics and citations.

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