Redox signaling modulates nitrite transport in a commensal Streptococcus

Area of Science:

• Microbiology
• Biochemistry
• Oral Health

Background:

• Commensal streptococci, including Streptococcus parasanguinis, maintain oral homeostasis via hydrogen peroxide (H2O2) production.
• H2O2 from S. parasanguinis reacts with environmental nitrite (NO2) to form reactive nitrogen species (RNS), aiding pathogen antagonism.
• Pyruvate oxidase (PoxL) is essential for H2O2 production by S. parasanguinis, but its role in NO2 acquisition is unclear.

Purpose of the Study:

• To investigate the role of pyruvate oxidase (PoxL) in Streptococcus parasanguinis nitrite (NO2) transport.
• To determine the impact of PoxL on NO2-dependent fitness and physiology in S. parasanguinis.
• To elucidate the regulatory interplay between H2O2 production and NO2 metabolism.

Main Methods:

• Utilized a Drosophila melanogaster colonization model to assess bacterial fitness.
• Quantified intracellular nitrite levels in wild-type and poxL mutant strains.
• Analyzed the expression of the formate-nitrite transporter (Spaf_1142) using quantitative methods.
• Assessed glycolytic protein levels and ATP production.

Main Results:

• Loss of PoxL impaired biofilm development and colonization, which was restored by exogenous NO2.
• The poxL mutant exhibited reduced intracellular NO2 levels and decreased expression of the formate-nitrite transporter (Spaf_1142).
• PoxL deficiency led to decreased glycolytic proteins and ATP production, partially rescued by nitrite addition.

Conclusions:

• PoxL activity and H2O2 production are critical for regulating NO2 transport and metabolism in S. parasanguinis.
• This highlights a coordinated mechanism linking H2O2 generation to nutrient acquisition and bacterial physiology.
• Findings provide insights into the complex interactions governing oral microbial communities and host-microbe homeostasis.