Scattering angle resolved optical coherence tomography measures morphological changes in Bacillus subtilis colonies.

Area of Science:

• Biophysics
• Microbiology
• Optical Imaging

Background:

• Early detection of neurological diseases is crucial, as current markers appear late.
• Subcellular changes, like mitochondrial dysfunction, precede widespread pathology.
• Bacterial morphology changes can serve as a model for detecting early subcellular alterations.

Purpose of the Study:

• To investigate the utility of scattering angle resolved optical coherence tomography (SAR-OCT) for detecting morphological changes in bacteria.
• To assess if SAR-OCT can identify shape transitions in *Bacillus subtilis*.

Main Methods:

• SAR-OCT was employed to analyze scattering angle distributions in *Bacillus subtilis*.
• The rod-to-coccus shape transition was imaged, and the low- to medium angle scattering ratio (L/M ratio) was analyzed.
• Bacterial orientation within colonies was modeled and compared with SAR-OCT findings.

Main Results:

• Significant differences in backscattering angle distribution were observed during the rod-to-coccus transition.
• The Burr distribution's $\Phi$-parameter of the SAR-OCT-derived L/M ratio was significantly lower in cocci than in rods.
• SAR-OCT-derived L/M ratio variations correlated with predicted bacterial orientations within colonies.

Conclusions:

• SAR-OCT demonstrates potential for detecting bacterial morphological changes.
• This technique could be valuable for early detection of cellular alterations relevant to disease.