The major facilitator superfamily-type transporter YmfE and the multidrug-efflux activator Mta mediate bacillibactin secretion in Bacillus subtilis.
High-affinity iron acquisition in Bacillus subtilis is mediated via the bacillibactin catechole siderophore pathway. Three of the four essential pathway steps, bacillibactin synthesis, Fe-bacillibactin uptake, and Fe-bacillibactin hydrolysis have been characterized previously. The functional and regulatory components for bacillibactin secretion, the second step of the siderophore pathway, remained unknown. In this study, the screening of a B. subtilis exporter mutant library led to the identification of the YmfE major facilitator superfamily (MFS)-type transporter as a target for bacillibactin export. Analysis of iron-limited ymfE mutant cultures displayed an eightfold reduced bacillibactin secretion and, on the other hand, a 25-fold increased secretion of the bacillibactin precursor 2,3-dihydroxybenzoate. Investigation of the regulatory aspect revealed that bacillibactin secretion is, in contrast to all other components of the pathway, independent of the ferric uptake repressor Fur. Indeed, the MerR-type transcriptional regulator Mta was found to activate both bacillibactin secretion and ymfE gene expression, exposing Mta as an additional regulatory member of the bacillibactin pathway.
Miethke
Marcus
M
Fachbereich Chemie/Biochemie der Philipps-Universität Marburg, Hans Meerwein Strasse, D-35032 Marburg, Germany.
Schmidt
Sarah
S
Marahiel
Mohamed A
MA
D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D004952:Esters / Q000378:metabolism*; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D023061:Gene Order; D062385:Hydroxybenzoates / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009842:Oligopeptides / Q000378:metabolism*; D009876:Operon; D017433:Protein Structure, Secondary; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
D001426:Bacterial Proteins; D003470:Culture Media; D004952:Esters; D062385:Hydroxybenzoates; D026901:Membrane Transport Proteins; C119773:Mta protein, Bacillus subtilis; D009842:Oligopeptides; D015534:Trans-Activators; C430721:bacillibactin; C009135:2,3-dihydroxybenzoic acid; D007501:Iron