The tricarboxylic acid cycle in Shewanella oneidensis is independent of Fur and RyhB control
1 Department of Environmental Science and Engineering, Tsinghua University, Beijing 100084, China
2 Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
3 Pacific Northwest National Laboratory, Richland, WA 99352, USA
4 Department of Biostatistics and Bioinformatics, Duke University, Durham, NC 27710, USA
5 Institute for Environmental Genomics and Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USA
BMC Microbiology 2010, 10:264 doi:10.1186/1471-2180-10-264Published: 16 October 2010
It is well established in E. coli and Vibrio cholerae that strains harboring mutations in the ferric uptake regulator gene (fur) are unable to utilize tricarboxylic acid (TCA) compounds, due to the down-regulation of key TCA cycle enzymes, such as AcnA and SdhABCD. This down-regulation is mediated by a Fur-regulated small regulatory RNA named RyhB. It is unclear in the γ-proteobacterium S. oneidensis whether TCA is also regulated by Fur and RyhB.
In the present study, we showed that a fur deletion mutant of S. oneidensis could utilize TCA compounds. Consistently, expression of the TCA cycle genes acnA and sdhA was not down-regulated in the mutant. To explore this observation further, we identified a ryhB gene in Shewanella species and experimentally demonstrated the gene expression. Further experiments suggested that RyhB was up-regulated in fur mutant, but that AcnA and SdhA were not controlled by RyhB.
These cumulative results delineate an important difference of the Fur-RyhB regulatory cycle between S. oneidensis and other γ-proteobacteria. This work represents a step forward for understanding the unique regulation in S. oneidensis.