Second-order functions are the simplest correlations between flow cytometric light scatter and bacterial diameter

Area of Science:

• Microbiology
• Biophysics
• Analytical Chemistry

Background:

• Accurately measuring bacterial cell diameter is crucial for understanding microbial physiology.
• Flow cytometry offers a high-throughput method for analyzing cellular properties, including forward light scatter (FSC).
• Directly correlating FSC with precise bacterial cell diameter is challenging due to technical limitations.

Purpose of the Study:

• To investigate the mathematical relationships between bacterial cell diameter and flow cytometric forward light scatter.
• To determine if linear or non-linear models best describe this relationship.
• To establish a method for estimating bacterial size from FSC data.

Main Methods:

• Analysis of bacterial cell diameter using an electric particle analyzer.
• Measurement of forward light scatter (FSC) using flow cytometry.
• Development and application of second-order mathematical models to relate diameter and FSC data.

Main Results:

• Standard regression techniques are unsuitable due to the inability to measure individual cell diameter and FSC simultaneously.
• A monotone increasing function was assumed to model the relationship between cell diameter and FSC.
• Forward light scatter data cannot be accurately and universally transformed into bacterial size using a linear function.

Conclusions:

• Second-order mathematical relationships provide a satisfactory model for correlating bacterial cell diameter and forward light scatter in eubacteria.
• Non-linear modeling is necessary for accurately relating FSC measurements to bacterial size.
• These findings advance the quantitative analysis of bacterial populations using flow cytometry.