High‐precision characterization of individual E. coli cell morphology by scanning flow cytometry

Abstract

We demonstrate a flow-cytometric method to measure length and diameter of single Escherichia coli cells with sub-diffraction precision. The method is based on the original scanning flow cytometer that measures angle-resolved light-scattering patterns (LSPs) of individual particles. We modeled the shape of E. coli cells as a cylinder capped with hemispheres of the same radius, and simulated light scattering by the models using the discrete dipole approximation. We computed a database of the LSPs of individual bacteria in a wide range of model parameters and used it to solve the inverse light-scattering problem by the nearest-neighbor interpolation. The solution allows us to determine length and diameter of each individual bacterium, including uncertainties of these estimates. The developed method was tested on two strains of E. coli. The resulting precision of bacteria length and diameter measurements varied from 50 nm to 250 nm and from 5 nm to 25 nm, respectively. The measured distributions of samples over length and diameter were in good agreement with measurements performed by optical microscopy and literature data. The described approach can be applied for rapid morphological characterization of any rod-shaped bacteria. ' 2013 International Society for Advancement of Cytometry

Advanced consumable‐free morphological analysis of intact red blood cells by a compact scanning flow cytometer

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“…The core of the characterization method is the solution of the inverse light-scattering (ILS) problem, using a parametric shape model of the characterized particle (24,25). This approach has been successfully applied to RBCs (26,27), as well as to other biological particles, including platelets, bacteria, blood microparticles, and milk fat globules (24,(28)(29)(30)(31). Conceptually similar approach, based on LSP measurement combined with fitting theoretical LSPs, has been recently demonstrated for determination of RBC diameters in a microfluidic channel (32).…”

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