This family consists of an exoribonuclease, ribonuclease R, also called VacB. It is one of the eight exoribonucleases reported in E. coli and is broadly distributed throughout the bacteria. In E. coli, double mutants of this protein and polynucleotide phosphorylase are not viable. Scoring between trusted and noise cutoffs to the model are shorter, divergent forms from the Chlamydiae, and divergent forms from the Campylobacterales (including Helicobacter pylori) and Leptospira interrogans. [Transcription, Degradation of RNA]