The IMES-2 RNA motif is a conserved RNA structure that was identified by a study based on metagenomics and bioinformatics,[1] and the underlying RNA sequences were identified independently by a similar earlier study.
[2] These RNAs are present in environmental sequences, and when discovered were not known to be present in any cultivated species.
However, an IMES-2 RNA has been detected in alphaproteobacterium HIMB114, which is classified in the SAR11 clade of marine bacteria.
This finding fits with earlier predictions that species that use IMES-2 RNAs are most closely related to alphaproteobacteria.
[2][3] Only two bacterial RNAs are known (6S RNA and transfer RNA) to be more highly transcribed than ribosomes.