AdcBC-dependent zinc uptake influences physiological responses in Streptococcus mutans

Area of Science:

• Oral microbiology
• Bacterial physiology
• Zinc transport

Background:

• Zinc's antimicrobial properties are vital in oral care products.
• The molecular mechanisms of zinc's influence on Streptococcus mutans (S. mutans) are not fully understood.
• The AdcABC system is the main high-affinity zinc transporter in S. mutans.

Purpose of the Study:

• To investigate the physiological responses of S. mutans lacking the AdcABC zinc transporter.
• To determine the role of AdcABC-mediated zinc uptake in S. mutans.
• To elucidate zinc's uptake-dependent and independent effects on S. mutans.

Main Methods:

• Compared wild-type, ΔadcBC mutant, and complemented S. mutans strains.
• Assessed growth, carbohydrate utilization, acidogenicity, acid tolerance, aggregation, and biofilm formation.
• Analyzed gene expression related to stress response and regulation under varying zinc conditions.

Main Results:

• Loss of adcBC impaired growth and carbohydrate metabolism, with partial recovery upon zinc supplementation.
• AdcABC deficiency altered expression of genes involved in fermentation, oxidative stress, and metal homeostasis.
• Zinc enhanced aggregation and surface attachment independently of AdcABC, while biofilm formation was partially dependent on it.

Conclusions:

• Loss of adcBC significantly alters S. mutans physiology.
• Zinc impacts bacterial physiology via both uptake-dependent and independent mechanisms.
• Zinc's role in the oral environment is context-dependent.