Urease activity in Streptococcus salivarius at low pH

Area of Science:

• Microbiology
• Oral Health
• Bacterial Metabolism

Background:

• Arginine deiminase system in oral bacteria enhances acid tolerance by producing alkali.
• The role of urease activity in Streptococcus salivarius for acid tolerance was investigated.

Purpose of the Study:

• To examine the potential of Streptococcus salivarius urease to confer acid tolerance.
• To understand the pH stability and activity range of urease in intact cells versus cell extracts.

Main Methods:

• Assessed urease activity in cell extracts and intact Streptococcus salivarius cells across a range of pH values.
• Investigated urease stability and ammonia generation under acidic conditions (pH 2.3-4.3).
• Examined the effect of membrane compromise on urease activity and stability.

Main Results:

• Streptococcus salivarius urease exhibits optimal activity between pH 5.0-8.0 and is rapidly inactivated below pH 4.3.
• Intact cells demonstrate broader pH tolerance, retaining urease activity and rapidly increasing pH even after exposure to pH 2.6.
• Urease in intact cells is protected from rapid inactivation, enabling significant pH rise for at least 1 hour despite progressive cell death.

Conclusions:

• Intact Streptococcus salivarius cells protect urease, allowing ammonia generation to buffer acidic environments.
• Urease contributes to acid tolerance in Streptococcus salivarius, extending survival in low pH conditions.
• Cellular protection mechanisms are crucial for urease function in extreme pH environments relevant to oral health.