RNase I regulates Escherichia coli 2⁰,3⁰-cyclic nucleotide monophosphate levels and biofilm formation

Regulation of nucleotide and nucleoside concentrations is critical for faithful DNA replication, transcription, and translation in all organisms, and has been linked to bacterial biofilm formation. Unusual 2⁰,3⁰-cyclic nucleotide monophosphates (2⁰,3⁰-cNMPs) recently were quantified in mammalian systems, and previous reports have linked these nucleotides to cellular stress and damage in eukaryotes, suggesting an intriguing connection with nucleotide/nucleoside pools and/or cyclic nucleotide signaling. This work reports the first quantification of 2⁰,3⁰-cNMPs in Escherichia coli and demonstrates that 2⁰,3⁰-cNMP levels in E. coli are generated specifically from RNase I-catalyzed RNA degradation, presumably as part of a previously unidentified nucleotide salvage pathway. Furthermore, RNase I and 2⁰,3⁰-cNMP levels are demonstrated to play an important role in controlling biofilm formation. This work identifies a physiological role for cytoplasmic RNase I and constitutes the first progress toward elucidating the biological functions of bacterial 2⁰,3⁰-cNMPs.