Creatine utilization as a sole nitrogen source in KT2440 is transcriptionally regulated by CahR.

Glutamine amidotransferase-1 domain-containing AraC-family transcriptional regulators (GATRs) are present in the genomes of many bacteria, including all species. The involvement of several characterized GATRs in amine-containing compound metabolism has been determined, but the full scope of GATR ligands and regulatory networks are still unknown. Here, we characterize 's detection of the animal-derived amine compound creatine, a compound particularly enriched in muscle and ciliated cells by a creatine-specific GATR, PP_3665, here named CahR (Creatine amidohydrolase Regulator). is necessary for transcription of the gene encoding creatinase () in the presence of creatine and is critical for s ability to utilize creatine as a sole source of nitrogen. The CahR/creatine regulon is small, and an electrophoretic mobility shift assay demonstrates strong and specific CahR binding only at the promoter, supporting the conclusion that much of the regulon is dependent on downstream metabolites. Phylogenetic analysis of orthologues associated with orthologues highlights a strain distribution and organization supporting probable horizontal gene transfer, particularly evident within the genus . This study identifies and characterizes the GATR that transcriptionally controls 's metabolism of creatine, broadening the scope of known GATR ligands and suggesting GATR diversification during evolution of metabolism for aliphatic nitrogen compounds.