%0 Journal Article %A Leach, Lynne H. %A Lewis, Thomas A. %T Identification and characterization of Pseudomonas membrane transporters necessary for utilization of the siderophore pyridine-2,6-bis(thiocarboxylic acid) (PDTC) %D 2006 %J Microbiology, %V 152 %N 10 %P 3157-3166 %@ 1465-2080 %R https://doi.org/10.1099/mic.0.29116-0 %K Cm, chloramphenicol %K CT, carbon tetrachloride %K PDTC, pyridine-2,6-bis(thiocarboxylic acid) %K Tc, tetracycline %K Fur, ferric uptake regulator %K Km, kanamycin %K Gm, gentamicin %K o-p, 1,10-phenanthroline %I Microbiology Society, %X The compound pyridine-2,6-bis(thiocarboxylic acid) (PDTC) is known to be produced and excreted by three strains of Pseudomonas. Its reactivity includes the complete dechlorination of the environmental contaminant carbon tetrachloride. PDTC functions as a siderophore; however, roles as a ferric reductant and antimicrobial agent have also been proposed. PDTC function and regulation were further explored by characterizing the phenotypes of mutants in predicted membrane transporter genes. The functions of a predicted outer-membrane transporter (PdtK) and a predicted inner-membrane permease (PdtE) were examined in Pseudomonas putida DSM 3601. Uptake of iron from 55Fe(III):PDTC, and bioutilization of PDTC in a chelated medium, were dependent upon PdtK and PdtE. Another strain of P. putida (KT2440), which lacks pdt orthologues, showed growth inhibition by PDTC that could be relieved by introducing a plasmid containing pdtKCPE. Transcriptional activation in response to exogenously added PDTC (25 μM) was unaltered by the pdtK or pdtE mutations; each mutant showed activation of a pdt transcriptional reporter, indistinguishable from an isogenic PDTC utilization-proficient strain. The data demonstrate that PdtK and PdtE constitute a bipartite outer-membrane/inner-membrane transport system for iron acquisition from Fe(III):PDTC. Disruptions in this portion of the P. putida DSM 3601 pdt gene cluster do not abolish PDTC-dependent transcriptional signalling. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.29116-0