LiaSR two-component system modulates the oxidative stress response in Streptococcusmutans

Area of Science:

• Microbiology
• Molecular Biology
• Dental Research

Background:

• Commensal oral bacteria produce reactive oxygen species (ROS) that inhibit pathogenic Streptococcus mutans (S. mutans).
• The LiaSR two-component system in S. mutans is known to sense oxidative stress, but its molecular mechanisms remain unclear.

Purpose of the Study:

• To elucidate the molecular mechanisms of the LiaSR two-component system in mediating the oxidative stress response in S. mutans.
• To investigate the role of LiaSR in S. mutans's sensitivity to hydrogen peroxide (H₂O₂).

Main Methods:

• Hydrogen peroxide (H₂O₂) killing assays and confocal laser scanning microscopy.
• Propidium iodide staining, TUNEL assays, and quantitative real-time PCR (qRT-PCR).
• Analysis of gene expression, including spxA2, dpr, and dinB.

Main Results:

• S. mutans mutants deficient in liaS or liaR were hypersensitive to H₂O₂, exhibiting increased ROS levels and membrane permeability.
• The liaR mutant showed higher DNA fragmentation rates, and expression of spxA2, dpr, and dinB genes was altered.
• The LiaSR system influences spxA2 expression and contributes to membrane homeostasis during oxidative stress.

Conclusions:

• The LiaSR two-component system is critical for S. mutans's oxidative stress response and survival.
• LiaSR modulates gene expression, including spxA2, dpr, and dinB, to maintain cellular integrity and reduce DNA damage.
• Understanding LiaSR function provides insights into S. mutans pathogenesis and potential therapeutic targets for dental caries.