Disruption of a fur-Like Gene Inhibits Magnetosome Formation in Magnetospirillum gryphiswaldense MSR-1

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Huang Yijun, Zhang Weijia, Jiang Wei, Rong Chengbo, and Li Ying^*

State Key Laboratories for Agrobiotechnology and College of Biological Sciences, China Agricultural University, Beijing 100094, China; fax: (86) 10628-95232; E-mail: yingli528@vip.sina.com

^* To whom correspondence should be addressed.

Received May 2, 2007; Revision received May 15, 2007

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In this study, a genomic library of Magnetospirillum gryphiswaldense MSR-1 strain was constructed and a fur-like gene (encoding Fur protein, ferric uptake regulator) 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-1, 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 H₂O₂ at 10-fold higher level than wild-type. These data suggest that Fur protein may possess a novel function in magnetic bacteria.

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KEY WORDS: Magnetospirillum gryphiswaldense, ferric uptake regulator (Fur), magnetosome formation

DOI: 10.1134/S0006297907110119

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