Dataset Information

Characterization of the Shewanella oneidensis Fur gene: roles in iron and acid tolerance response.

ABSTRACT:

Background

Iron homeostasis is a key metabolism for most organisms. In many bacterial species, coordinate regulation of iron homeostasis depends on the protein product of a Fur gene. Fur also plays roles in virulence, acid tolerance, redox-stress responses, flagella chemotaxis and metabolic pathways.

Results

We conducted physiological and transcriptomic studies to characterize Fur in Shewanella oneidensis, with regard to its roles in iron and acid tolerance response. A S. oneidensisfur deletion mutant was defective in growth under iron-abundant or acidic environment. However, it coped with iron depletion better than the wild-type strain MR-1. Further gene expression studies by microarray of the fur mutant confirmed previous findings that iron uptake genes were highly de-repressed in the mutant. Intriguingly, a large number of genes involved in energy metabolism were iron-responsive but Fur-independent, suggesting an intimate relationship of energy metabolism to iron response, but not to Fur. Further characterization of these genes in energy metabolism suggested that they might be controlled by transcriptional factor Crp, as shown by an enriched motif searching algorithm in the corresponding cluster of a gene co-expression network.

Conclusion

This work demonstrates that S. oneidensis Fur is involved in iron acquisition and acid tolerance response. In addition, analyzing genome-wide transcriptional profiles provides useful information for the characterization of Fur and iron response in S. oneidensis.

SUBMITTER: Yang Y

PROVIDER: S-EPMC2386053 | biostudies-literature | 2008

REPOSITORIES: biostudies-literature

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Publications

Characterization of the Shewanella oneidensis Fur gene: roles in iron and acid tolerance response.

Yang Yunfeng Y Harris Daniel P DP Luo Feng F Wu Liyou L Parsons Andrea B AB Palumbo Anthony V AV Zhou Jizhong J

BMC genomics 20080101

<h4>Background</h4>Iron homeostasis is a key metabolism for most organisms. In many bacterial species, coordinate regulation of iron homeostasis depends on the protein product of a Fur gene. Fur also plays roles in virulence, acid tolerance, redox-stress responses, flagella chemotaxis and metabolic pathways.<h4>Results</h4>We conducted physiological and transcriptomic studies to characterize Fur in Shewanella oneidensis, with regard to its roles in iron and acid tolerance response. A S. oneidens ...[more]

PMID: 18366600

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Project description:BACKGROUND: Iron homeostasis of Shewanella oneidensis, a gamma-proteobacterium possessing high iron content, is regulated by a global transcription factor Fur. However, knowledge is incomplete about other biological pathways that respond to changes in iron concentration, as well as details of the responses. In this work, we integrate physiological, transcriptomics and genetic approaches to delineate the iron response of S. oneidensis. RESULTS: We show that the iron response in S. oneidensis is a rapid process. Temporal gene expression profiles were examined for iron depletion and repletion, and a gene co-expression network was reconstructed. Modules of iron acquisition systems, anaerobic energy metabolism and protein degradation were the most noteworthy in the gene network. Bioinformatics analyses suggested that genes in each of the modules might be regulated by DNA-binding proteins Fur, CRP and RpoH, respectively. Closer inspection of these modules revealed a transcriptional regulator (SO2426) involved in iron acquisition and ten transcriptional factors involved in anaerobic energy metabolism. Selected genes in the network were analyzed by genetic studies. Disruption of genes encoding a putative alcaligin biosynthesis protein (SO3032) and a gene previously implicated in protein degradation (SO2017) led to severe growth deficiency under iron depletion conditions. Disruption of a novel transcriptional factor (SO1415) caused deficiency in both anaerobic iron reduction and growth with thiosulfate or TMAO as an electronic acceptor, suggesting that SO1415 is required for specific branches of anaerobic energy metabolism pathways. CONCLUSION: Using a reconstructed gene network, we identified major biological pathways that were differentially expressed during iron depletion and repletion. Genetic studies not only demonstrated the importance of iron acquisition and protein degradation for iron depletion, but also characterized a novel transcriptional factor (SO1415) with a role in anaerobic energy metabolism.

Project description:Iron, a major protein cofactor, is essential for most organisms but can simultaneously be toxic. Iron homeostasis thus has to be effectively maintained under a range of iron regimes. This may be particularly true with Shewanella oneidensis, a representative of dissimilatory metal-reducing bacteria (DMRB), which are capable of respiring a variety of chemicals as electron acceptors (EAs), including iron ores. Although iron respiration and its regulation have been extensively studied in this bacterium, how iron homeostasis is maintained remains largely unknown. Here, we report that the loss of the iron homeostasis master regulator Fur negatively affects the respiration of all EAs tested. This defect appears mainly to be a result of reduced cytochrome c (cyt c) production, despite a decrease in the expression of reductases that are under the direct control of Fur. We also show that S. oneidensis Fur interacts with canonical Fur box motifs in F-F-x-R configuration rather than the palindromic motif proposed before. The fur mutant has lowered total iron and increased free iron contents. Under iron-rich conditions, overproduction of the major iron storage protein Bfr elevates the total iron levels of the fur mutant over those of the wild-type but does not affect free iron levels. Intriguingly, such an operation only marginally improves cyt c production by affecting heme b biosynthesis. It is established that iron dictates heme b/cyt c biosynthesis in S. oneidensisfur+ strains, but the fur mutation annuls the dependence of heme b/cyt c biosynthesis on iron. Overall, our results suggest that Fur has a profound impact on the iron homeostasis of S. oneidensis, through which many physiological processes, especially respiration, are transformed.IMPORTANCE Iron reduction is a signature of S. oneidensis, and this process relies on a large number of type c cytochromes, which per se are iron-containing proteins. Thus, iron plays an essential and special role in iron respiration, but to date, the nature of iron metabolism and regulation of the bacterium remains largely unknown. In this study, we investigated impacts of Fur, the master regulator of iron homeostasis, on respiration. The loss of Fur causes a general defect in respiration, a result of impaired cyt c production rather than specific regulation. Additionally, the fur mutant is unresponsive to iron, resulting in imbalanced iron homeostasis and dissociation between iron and cyt c production. These findings provide important insights into the iron biology of DMRB.

Dataset Information

Characterization of the Shewanella oneidensis Fur gene: roles in iron and acid tolerance response.

Background

Results

Conclusion

Publications

Characterization of the Shewanella oneidensis Fur gene: roles in iron and acid tolerance response.

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