Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:1.7.1.4 (
nitrite reductase
)
1,847
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Under anoxic conditions, many bacteria including
Shewanella loihica
PV-4 strain could use nitrate as electron acceptors for dissimilatory nitrate reduction to ammonium (DNRA) and/or denitrification. Previous and current studies have shown that DNRA is favored under higher ambient carbon-to-nitrogen (C/N) ratios while denitrification is upregulated under lower C/N ratios, which is consistent with our bioenergetics calculations. Interestingly, computational analyses indicate that the common cyclic AMP receptor protein (designated
CRP1
) and its paralogue CRP2 might be both involved in the regulation of two competing dissimilatory nitrate reduction pathways, DNRA and denitrification, in
S. loihica
PV-4 and several other denitrifying
Shewanella
species. To explore the regulatory mechanism underlying the DNR pathways, nitrate reduction of a series of in-frame deletion mutants was analyzed and compared under different C/N ratios. Deletion of
crp1
could accelerate reduction of nitrite to NO under both low and high C/N ratios.
CRP1
is not required for denitrification and actually suppresses production of NO and N
2
O gases. Deletion of either NO-forming
nitrite reductase
gene
nirK
or
crp2
blocked production of NO gas. Furthermore, real-time PCR and electrophoretic mobility shift assays (EMSAs) demonstrated that the transcription of DNRA-relevant genes such as
nap-beta
(
napDABGH
),
nrfA
and
cymA
genes were upregulated by
CRP1
, while
nirK
transcription was dependent on CRP2. There are tradeoffs between the different physiological roles of nitrate/lactate as nitrogen nutrient/carbon source and electron acceptor/donor and CRPs may leverage dissimilatory nitrate reduction pathways for maximizing energy yield and bacterial survival under ambient environments.
Importance
Some microbes utilize different dissimilatory nitrate reduction (DNR) pathways, including DNR to ammonia (DNRA) and denitrification, for anaerobic respiration in response to ambient carbon/nitrogen ratio changes. Large-scale industrial nitrogen fixation and fertilizer application raise the concern of emission of N
2
O, a stable gas with a potent global warming potential, as consequence of microbial respiration, hereby aggravating global warming and climate change. However, little is known about the molecular mechanism underlying the choice of two competing DNR pathways. We demonstrate that the global regulator
CRP1
widely encoded in bacteria is required for DNRA in
S. loihica
PV-4 strain while the CRP2 paralogue is required for transcription of
nitrite reductase
gene
nirK
for denitrification. Sufficient carbon source leads to the predominance of DNRA, while carbon source/electron donor deficiency may result in an incomplete denitrification process, raising the concern of high levels of N
2
O emission from nitrate-rich and carbon source-poor waters and soils.
...
PMID:DNRA and denitrification pathways are leveraged by cyclic AMP receptor protein (CRP) paralogues based on electron donor/acceptor limitation in
Shewanella loihica
PV-4. 3315 88
