Rho-dependent termination enables cellular pH homeostasis.

Area of Science:

• Bacteriology
• Molecular Biology
• Biochemistry

Background:

• The Rho termination factor is crucial for bacterial genome integrity by controlling transcription.
• Rho's role in regulating intracellular pH has not been previously understood.

Purpose of the Study:

• To investigate the direct link between Rho factor function and bacterial intracellular pH homeostasis.
• To elucidate the molecular mechanisms by which Rho influences cellular pH.

Main Methods:

• Studied Rho-deficient and Rho-overexpressing *Escherichia coli* strains.
• Measured intracellular pH using pH indicators.
• Assessed tryptophanase-A (TnaA) activity and ammonia production.
• Performed *in vivo* termination assays and RNA release assays.

Main Results:

• Loss of Rho function elevated intracellular pH (>8.0) due to upregulated TnaA activity and ammonia production.
• Rho overexpression decreased intracellular pH (~6.2), potentially from ATP hydrolysis by excess Rho.
• Rho-mediated termination efficiency is modulated by pH, with alkaline pH stimulating catalytic activity and acidic pH increasing Rho levels.

Conclusions:

• Rho factor plays a significant role in maintaining bacterial intracellular pH homeostasis.
• Alkalization results from Rho deficiency and ammonia production, while acidification stems from Rho overexpression and ATP hydrolysis.
• This pH-Rho connection has broad implications for bacterial physiology and gene expression.