Size determination of Streptococcus mutans 10499 by laser light scattering

Area of Science:

• Microbiology
• Optical Physics
• Biophysics

Background:

• Accurate measurement of bacterial size is crucial for understanding microbial behavior.
• Streptococcus mutans has dimensions comparable to the wavelength of light, posing measurement challenges.

Purpose of the Study:

• To determine the mean size of Streptococcus mutans 10449 using three distinct optical techniques.
• To compare the efficacy and consistency of different optical measurement methods for bacterial sizing.

Main Methods:

• Homodyne time correlation spectroscopy: measures diffusion coefficient using laser light coherence.
• Power spectrum spectroscopy: determines diffusion coefficient, relying on laser light properties.
• Differential light scattering: analyzes angular distribution of scattered light for size interpretation.

Main Results:

• All three optical methods provided consistent measurements for the bacterial radius.
• Mean radius values obtained were 0.324 ± 0.006 μm, 0.0325 ± 0.007 μm, and 0.315 ± 0.009 μm.
• Measurements showed favorable comparison with polystyrene sphere standards.

Conclusions:

• Optical methods can reliably determine the size of Streptococcus mutans.
• Intensity correlation spectroscopy is highlighted as a preferred technique due to its ability to directly assess sample polydispersity.