The tricarboxylic acid cycle in Shewanella oneidensis is independent of Fur and RyhB control.
BACKGROUND
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.


RESULTS
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.


CONCLUSIONS
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.
Yang
Yunfeng
Y
Department of Environmental Science and Engineering, Tsinghua University, Beijing 100084, China. yangyf@tsinghua.edu.cn
McCue
Lee Ann
LA
Parsons
Andrea B
AB
Feng
Sheng
S
Zhou
Jizhong
J
D000154:Aconitate Hydratase / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002244:Carbon / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D002952:Citric Acid Cycle / Q000235:genetics*; D005420:Flavoproteins / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D016133:Polymerase Chain Reaction; D012329:RNA, Bacterial / Q000235:genetics* / Q000378:metabolism; D022661:RNA, Untranslated / Q000235:genetics* / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D017384:Sequence Deletion; D020592:Shewanella / Q000235:genetics* / Q000378:metabolism*
D001426:Bacterial Proteins; D005420:Flavoproteins; D012329:RNA, Bacterial; D022661:RNA, Untranslated; D012097:Repressor Proteins; C084271:SdhA protein, Bacteria; C068477:ferric uptake regulating proteins, bacterial; D002244:Carbon; D000154:Aconitate Hydratase