title: Identification and characterization of Pseudomonas membrane transporters necessary for utilization of the siderophore pyridine-2,6-bis(thiocarboxylic acid) (PDTC).
abstract: 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 (55)Fe(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 muM) 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.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Vermont, 95 Carrigan Drive, Burlington, VT 05405, USA.
authors.forename: Lynne H
authors.initials: LH
authors.lastname: Leach
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Vermont, 95 Carrigan Drive, Burlington, VT 05405, USA.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Lewis
mesh_terms: D019677:Artificial Gene Fusion; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D007501:Iron / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D016958:Pseudomonas putida / Q000235:genetics / Q000378:metabolism*; D011725:Pyridines / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001425:Bacterial Outer Membrane Proteins; D026901:Membrane Transport Proteins; D011725:Pyridines; D011956:Receptors, Cell Surface; C120960:pyridine-2,6-bis(thiocarboxylic acid); C035902:siderophore receptors; D007501:Iron