Scanning electron microscopic study of Streptococcus mutans BHT lysed by lysozyme

Area of Science:

• Microbiology
• Biochemistry
• Cell Biology

Background:

• Streptococcus mutans is a key pathogen in dental caries.
• Lysozymes are enzymes with known antibacterial properties.
• Understanding lysozyme's effect on bacterial cell walls is crucial for developing new antimicrobial strategies.

Purpose of the Study:

• To investigate the effects of purified salivary lysozyme (HSL) and hen egg white lysozyme (HEWL) on the surface structure of Streptococcus mutans BHT.
• To assess the bacteriolytic activity of HSL and HEWL against Streptococcus mutans.

Main Methods:

• Scanning electron microscopy (SEM) was used to visualize structural changes in Streptococcus mutans cells.
• Bacteriolysis was quantified by measuring the release of 3H-thymidine from pre-labeled bacteria.
• Comparative analysis of HSL and HEWL efficacy at specified concentrations and time points.

Main Results:

• Control Streptococcus mutans cells retained their normal morphology and intact cell walls.
• Exposure to HSL (5.0 U/ml) or HEWL (5.0 µg/ml) for 3 and 18 hours led to progressive destruction of bacterial cell structure.
• SEM revealed cell wall ruptures, spherical swellings, and extensive disruption, particularly in the septal areas, after 18 hours.
• Biochemical assays confirmed the observed bacteriolysis, correlating with structural damage.

Conclusions:

• Both purified salivary lysozyme (HSL) and hen egg white lysozyme (HEWL) effectively degrade the cell surface structure of Streptococcus mutans.
• The observed morphological changes and thymidine release indicate significant bacteriolysis induced by both lysozyme types.
• These findings support the potential of lysozymes as agents against Streptococcus mutans infections.