The first is a two component regulatory system that senses the presence of ethanolamine and the second mechanism is a AdoCbl riboswitch that senses the presence of AdoCbl, a cofactor needed for the breakdown of ethanolamine.
While the process of artificial engineering of nucleic acid ligands is highly interesting to biology and biotechnology, the notion of aptamers in the natural world had yet to be uncovered until 2002 when two groups led by Ronald Breaker and Evgeny Nudler discovered a nucleic acid-based genetic regulatory element (which was named riboswitch) that possesses similar molecular recognition properties to the artificially made aptamers.
For example, a riboswitch can directly bind a small target molecule, the binding of the target affects the gene's activity.
In bacteria, two classes of riboswitch are known to regulate genes that are involved in the synthesis or transport of pre-queuosine1, a precursor to queuosine: PreQ1-I riboswitches and PreQ1-II riboswitches.