A linear and circular dual-conformation noncoding RNA involves in oxidative stress tolerance of Bacillus altitudinis

Abstract Functional circular RNAs have been extensively studied in eukaryotes and progressively discovered in archaea, but not been identified in bacteria except some byproducts of self-spliced introns, devoid of biological function. In this study, using an experimental and computational pipeline, we confirm that a regulatory noncoding RNA DucS exists in both linear and circular conformations in Bacillus altitudinis . The 3’ end sequences of linear RNA are critical to RNA circularization. DucS promotes the tolerance of host to H 2 O 2 stress through its linear forms, partly due to upregulating the translation of a stress-responsive gene htrA , whereas its circular forms can promote the degradation of linear cognates. Through re-evaluating published RNA-seq data from 30 bacteria and experimental identification, we demonstrate that circular RNAs also exist in other bacteria, occurred unexpectedly in some well-known noncoding RNAs. Our results reveal firstly a functional circular RNA in bacteria, highlighting the universal existence of functional circular RNAs in all three domains of life.