Loss of topoisomerase I function affects the RpoS-dependent and GAD systems of acid resistance in Escherichia coli.

Acid resistance (AR) in Escherichia coli is important for its survival in the human gastrointestinal tract and involves three systems. The first AR system is dependent on the sigma factor RpoS. The second system (the GAD system) requires the glutamate decarboxylase isoforms encoded by the gadA and gadB genes.