Open AccessRegulation of the iron uptake genes in Pseudomonas fluorescens M114 by pseudobactin M114: the pbrA sigma factor gene does not mediate the siderophore regulatory response
Author(s) -
Callanan Michael,
Sexton Raymund,
Dowling David N.,
O'Gara Fergal
Publication year - 1996
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1996.tb08509.x
Subject(s) - siderophore , promoter , pseudomonas fluorescens , biology , mutant , sigma factor , gene , transcription (linguistics) , gene expression , microbiology and biotechnology , genetics , bacteria , linguistics , philosophy
The iron‐regulated PbrA sigma factor dictates the production of the siderophore, pseudobactin Ml 14, and its cognate outer membrane receptor, PbuA, in Pseudomonas fluorescens M114. However, the siderophore molecule also has a role in regulating the expression of the siderophore biosynthetic and siderophore receptor genes in P. fluorescens M114. This is based on the fact that β‐galactosidase levels from lacZ fusions of M114 siderophore promoters (biosynthetic and receptor) were reduced in M114 siderophore biosynthetic mutants compared to wild‐type M114. Expression of both promoters was increased by the addition of pseudobactin M114 to the growth medium. This effect was widespread and applicable to all but one of the siderophore negative strains of M114 tested. Furthermore, it was demonstrated that transcription of the pbrA sigma factor gene was not reduced in the siderophore biosynthetic mutants. This excludes the possibility that reduced expression of the siderophore biosynthetic and receptor promoters in the siderophore biosynthetic mutants is mediated at the level of expression of the pbrA gene itself. In addition, it was noted that the siderophore regulated response was applicable to promoters with and without the DNA sequence motif, (G/C)CTAAATCCC, which is required for iron‐regulated expression of some pseudomonad promoters.