D-Glutamate Utilization in Pseudomonas aeruginosa PAO1

D-Glutamate (D-Glu), an essential component of peptidoglycans, can be utilized as carbon and nitrogen source by Pseudomonas aeruginosa. DNA microarrays were employed to identify genes involved in D-Glu catabolism. Through gene knockout and growth phenotype analysis, the divergent dguR-dguABC (D-glutamate utilization) gene cluster was shown to participate in D-Glu catabolism and regulation. The dguA gene encodes a FAD-dependent D-amino acid dehydrogenase with D-Glu as its preferred substrate, and its promoter was specifically induced by exogenous D-Glu and D-Gln. The function of DguR as transcriptional activator of the dguABC operon was demonstrated by promoter activity measurements in vivo and by mobility shift assays with purified His-tagged DguR in vitro. Although the DNA-binding activity of DguR did not require D-Glu, the presence of D-Glu in the binding reaction was found to stabilize a preferred nucleoprotein complex. The dguB gene encodes a putative enamine/imine deaminase of the RidA family, but its role in D-Glu catabolism remained to be determined. While a lesion in dguC encoding a periplasmic solute binding protein did not affect growth on D-Glu, the AatJMQP transporter for acidic amino acid uptake was found essential for D-Glu and L-Glu utilization. Expression of this uptake system was subjected to induction by exogenous DL-Glu, most likely via the AauSR two-component system. In summary, DguA was identified in this study as a new member of the FAD-dependent amino acid dehydrogenase family for D-amino acid catabolism. DguR serves as a D-Glu sensor and transcriptional activator of the dguA promoter.

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He W, Li G, Yang CK, Lu CD