sentences:  The "Thermoanaerobacter tengcongensis" sequence AE013027 overlaps with that of purine riboswitch suggesting that the two riboswitches may work in conjunction to regulate the upstream gene which codes for TTE0584 (Q8RC62), a member of the permease family.Nelson et al.showed that this riboswitch senses and responds to guanidine and it was renamed Guanidine-I riboswitch.