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Open Access Research article

Role of a Fur homolog in iron metabolism in Nitrosomonas europaea

Neeraja Vajrala1, Luis A Sayavedra-Soto1, Peter J Bottomley2 and Daniel J Arp1*

Author Affiliations

1 Department of Botany and Plant Pathology, 2082 Cordley, Oregon State University, Corvallis OR 97331, USA

2 Department of Microbiology, 220 Nash, Oregon State University, Corvallis OR 97331, USA

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BMC Microbiology 2011, 11:37  doi:10.1186/1471-2180-11-37

Published: 21 February 2011

Abstract

Background

In response to environmental iron concentrations, many bacteria coordinately regulate transcription of genes involved in iron acquisition via the ferric uptake regulation (Fur) system. The genome of Nitrosomonas europaea, an ammonia-oxidizing bacterium, carries three genes (NE0616, NE0730 and NE1722) encoding proteins belonging to Fur family.

Results

Of the three N. europaea fur homologs, only the Fur homolog encoded by gene NE0616 complemented the Escherichia coli H1780 fur mutant. A N. europaea fur:kanP mutant strain was created by insertion of kanamycin-resistance cassette in the promoter region of NE0616 fur homolog. The total cellular iron contents of the fur:kanP mutant strain increased by 1.5-fold compared to wild type when grown in Fe-replete media. Relative to the wild type, the fur:kanP mutant exhibited increased sensitivity to iron at or above 500 μM concentrations. Unlike the wild type, the fur:kanP mutant was capable of utilizing iron-bound ferrioxamine without any lag phase and showed over expression of several outer membrane TonB-dependent receptor proteins irrespective of Fe availability.

Conclusions

Our studies have clearly indicated a role in Fe regulation by the Fur protein encoded by N. europaea NE0616 gene. Additional studies are required to fully delineate role of this fur homolog.