The Burkholderia cepacia fur gene: co-localization with omlA and absence of regulation by iron

The ferric uptake regulator (Fur) functions as a transcription repressor of many genes in bacteria in response to iron, but the presence of a function al equivalent of this protein has not been demonstrated in Burkholderia cep acia, A segment of the Burkholderia pseudomallei fur gene was amplified usi ng degenerate primers and used to identify chromosomal restriction fragment s containing the entire fur genes of B. cepacia and B. pseudomallei, These fragments were cloned and sequenced, revealing the Fur protein of both spec ies to be a polypeptide of 142 amino acids possessing a high degree of amin o acid sequence identity to Fur of other members of the beta subclass of th e Proteobacteria, Primer extension analysis demonstrated that transcription of B. cepacia fur originated from a single promoter located 36 bp upstream from the fur translation initiation codon, The Fur polypeptide of B. cepac ia was shown to functionally substitute for Fur in an Escherichia coli fur mutant. Single copy fur-lacZ fusions were constructed and used to examine t he regulation of B. cepacia fur, The B, cepacia fur promoter was not respon sive to iron availability, the presence of hydrogen peroxide or the superox ide generator methyl viologen. In addition, fur expression was not signific antly influenced by carbon source. Interestingly, the presence of the diver gently transcribed omlA/smpA gene upstream of fur in some members of the ga mma subclass of the Proteobacteria is retained in several genera within the beta taxon, including Burkholderia.