The Fibrobacter-1 RNA motif is a conserved RNA structure that was discovered by bioinformatics.Fibrobacter-1 motifs are found in organisms in the genus Fibrobacter, and in many metagenomic sequences. It is ambiguous whether Fibrobacter-1 RNAs function as cis-regulatory elements or whether they operate in trans. They are frequently located upstream of ribonuclease E (RNase E) genes, which is consistent with a cis-regulatory function. Additional cis-regulatory RNAs upstream of RNase E genes have already been established in other lineages of bacteria, e.g., the RNase E 5' UTR element. Some instances of the Fibrobacter-1 RNA motif are not located upstream of protein-coding genes. This observation could indicate that the RNAs function in trans as small RNAs. However, the affected instances are