Terahertz Imaging Detects Oral Cariogenic Microbial Domains Characteristics.

Area of Science:

• Microbiology
• Biophysics
• Dental Science

Background:

• Dental caries is a prevalent public health issue driven by plaque biofilms, primarily involving Streptococcus mutans.
• Streptococcus mutans produces an extracellular polysaccharide matrix (EPS) essential for cariogenic biofilm formation.
• The rnc-smc operon in S. mutans and interactions with other microbes like Candida albicans influence cariogenicity, but label-free detection remains challenging.

Purpose of the Study:

• To investigate the role of the S. mutans rnc-smc operon in EPS production.
• To explore the application of terahertz scanning near-field optical microscopy (THz s-SNOM) for label-free imaging of oral microbial biofilms.
• To observe monospecies and dual-species biofilms involving S. mutans and Candida albicans.

Main Methods:

• Utilized terahertz scanning near-field optical microscopy (THz s-SNOM) with light in the 0.1–0.3 THz range.
• Employed a nano-probe tip for point-by-point scanning and a dual kernel Gaussian filter for noise reduction.
• Scanned monospecies of streptococci, S. mutans smc/rnc mutants, and dual-species S. mutans-C. albicans biofilms.

Main Results:

• THz s-SNOM successfully generated near-field scanning images of S. mutans smc/rnc mutants, streptococci, and S. mutans-C. albicans dual-species.
• Image analysis revealed potential structural details of bacterial cells, including diameter and cell wall thickness.
• The study demonstrated the capability of THz s-SNOM to visualize bacterial cells and the EPS matrix.

Conclusions:

• The S. mutans rnc-smc operon plays a regulatory role in EPS production.
• THz s-SNOM is a promising novel technique for label-free detection and morphological observation of bacterial cells and EPS matrix in biofilms.
• This method has potential applications in studying cariogenic microbial interactions.