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Fnr (EtrA) acts as a fine-tuning regulator of anaerobic metabolism in Shewanella oneidensisMR-1
Ist Teil von
BMC microbiology, 2011-03, Vol.11 (1), Article 64
Erscheinungsjahr
2011
Link zum Volltext
Quelle
EZB Electronic Journals Library
Beschreibungen/Notizen
Abstract
Background
EtrA in
Shewanella oneidensis
MR-1, a model organism for study of adaptation to varied redox niches, shares 73.6% and 50.8% amino acid sequence identity with the oxygen-sensing regulators Fnr in
E. coli
and Anr in
Pseudomonas aeruginosa
, respectively; however, its regulatory role of anaerobic metabolism in
Shewanella
spp. is complex and not well understood.
Results
The expression of the
nap
genes,
nrfA, cymA
and
hcp
was significantly reduced in
etrA
deletion mutant EtrA7-1; however, limited anaerobic growth and nitrate reduction occurred, suggesting that multiple regulators control nitrate reduction in this strain. Dimethyl sulfoxide (DMSO) and fumarate reductase gene expression was down-regulated at least 2-fold in the mutant, which, showed lower or no reduction of these electron acceptors when compared to the wild type, suggesting both respiratory pathways are under EtrA control. Transcript analysis further suggested a role of EtrA in prophage activation and down-regulation of genes implicated in aerobic metabolism.
Conclusion
In contrast to previous studies that attributed a minor regulatory role to EtrA in
Shewanella
spp., this study demonstrates that EtrA acts as a global transcriptional regulator and, in conjunction with other regulators, fine-tunes the expression of genes involved in anaerobic metabolism in
S. oneidensis
strain MR-1. Transcriptomic and sequence analyses of the genes differentially expressed showed that those mostly affected by the mutation belonged to the "Energy metabolism" category, while stress-related genes were indirectly regulated in the mutant possibly as a result of a secondary perturbation (e.g. oxidative stress, starvation). We also conclude based on sequence, physiological and expression analyses that this regulator is more appropriately termed Fnr and recommend this descriptor be used in future publications.