, Volume 248, Issue 1, pp 17-24

A positive regulatory gene,pvdS, for expression of pyoverdin biosynthetic genes inPseudomonas aeruginosa PAO

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In response to iron limitationPseudomonas aeruginosa PAO induces production of pyoverdin, a low-molecular-weight siderophore able to capture ferric ion with a very high affinity. Thepvd genes involved in the pyoverdin biosynthesis are organized in a chromosomal region termed thepvd region, and expression of somepvd genes is regulated at the transcriptional level. Two sets of promoter regions for thepvd genes were defined that were transcriptionally derepressed under iron-limiting condition. Analysis of transcription from such promoters inEscherichia coli led to isolation and identification of a positive regulatory gene,pvdS, for expression of thepvd genes, andpvdS was localized in thepvd region. A genomicpvdS mutant of PAO, constructed by allelic exchange mutagenesis, produced no pyoverdin and did not allow transcription from thepvd promoters. Nucleotide sequence analysis revealed thatPvdS shows considerable similarity to FecI ofE. coli, a positive regulator for transcription of thefec (ferric citrate transport system) operon. The promoter region ofpvdS has the sequence that matches well the consensus binding site for theE. coli Fur protein, a global negative regulatory protein that represses the transcription of the ironrepressible genes. Consistent with the presence of such a consensus sequence, addition of iron repressed transcription of thepvdS gene inP. aeruginosa.

Communicated by M. Sekiguchi