Sorbitol transport by Streptococcus sanguis 160

Area of Science:

• Microbiology
• Biochemistry
• Oral Health

Background:

• Streptococcus sanguis is a common oral bacterium.
• Sorbitol is a sugar alcohol used in sugar-free products.
• Understanding bacterial sugar metabolism is crucial for oral health.

Purpose of the Study:

• To investigate the mechanisms of sorbitol metabolism in Streptococcus sanguis.
• To determine the role of nutrient availability in regulating sorbitol transport.
• To identify the specific transport systems involved in sorbitol uptake.

Main Methods:

• Continuous culture of S. sanguis under varying nutrient limitations (glucose, sorbitol, nitrogen).
• Measurement of [14C]-sorbitol uptake and enzyme activity assays (PEP phosphotransferase system).
• Kinetic analysis and crossover experiments with cell fractions.

Main Results:

• S. sanguis 160 possesses two sorbitol transport systems with different affinities.
• Sorbitol limitation induces a high-affinity sorbitol transport system.
• Sorbitol transport occurs exclusively via the PEP-phosphotransferase system (PTS).
• Sorbitol presence represses glucose PTS and induces sorbitol PTS.

Conclusions:

• Sorbitol metabolism in S. sanguis is tightly regulated by nutrient availability.
• Sorbitol limitation enhances sorbitol uptake through induction of a specific PTS.
• This adaptation is crucial for bacteria to utilize available nutrients in the oral environment.