Disruption of а<i> fur-</i>Like Gene Inhibits Magnetosome Formation in <i>Magnetospirillum gryphiswaldense </i>MSR-1
Ferric uptake regulator (Fur) is a key factor in the regulation of iron-dependent gene expression. In this report, a genomic library of Magnetospirillum gryphiswaldense MSR-1 strain was constructed and a/иг-like gene was isolated and sequenced. This gene consisted of 420 bp and encoded 139 amino acid residues. To investigate the function of this gene in MSR-I, a fur mutant was generated by double crossover with a kanamycin cassette inserted into its coding region. Iron uptake and magnetosome formation were dramatically inhibited by disruption of fur. Iron content analysis of the fur mutant indicated that it contained approximately 0.037% by dry weight, which was at least 10-fold less than that observed in the wild type. Electron microscopy revealed the absence of a magnetosome in the fur mutant, although it was able to tolerate 1 mM H202 at a 10-fold higher level than wild type. These data suggest that Fur may possess a novel function in magnetic bacteria.