sentences:  Furthermore, they demonstrated that bacteria are capable of endogenously producing guanidine and the riboswitch controls genes whose products are involved in modification or pumping out guanidine as a toxic compound from bacteria.Crystal structures of the riboswitch bound to the ligand have also been determined.The mini-ykkC RNA motif is a putative "cis"-regulatory element that apparently regulates similar genes to those regulated by the Guanidine-I riboswitch (ykkC/yxkD leader).