Document Detail

Synechococcus sp. strain PCC 7002 nifJ mutant lacking pyruvate:ferredoxin oxidoreductase.
MedLine Citation:
PMID:  21317262     Owner:  NLM     Status:  MEDLINE    
The nifJ gene codes for pyruvate:ferredoxin oxidoreductase (PFOR), which reduces ferredoxin during fermentative catabolism of pyruvate to acetyl-coenzyme A (acetyl-CoA). A nifJ knockout mutant was constructed that lacks one of two pathways for the oxidation of pyruvate in the cyanobacterium Synechococcus sp. strain PCC 7002. Remarkably, the photoautotrophic growth rate of this mutant increased by 20% relative to the wild-type (WT) rate under conditions of light-dark cycling. This result is attributed to an increase in the quantum yield of photosystem II (PSII) charge separation as measured by photosynthetic electron turnover efficiency determined using fast-repetition-rate fluorometry (F(v)/F(m)). During autofermentation, the excretion of acetate and lactate products by nifJ mutant cells decreased 2-fold and 1.2-fold, respectively. Although nifJ cells displayed higher in vitro hydrogenase activity than WT cells, H(2) production in vivo was 1.3-fold lower than the WT level. Inhibition of acetate-CoA ligase and pyruvate dehydrogenase complex by glycerol eliminated acetate production, with a resulting loss of reductant and a 3-fold decrease in H(2) production by nifJ cells compared to WT cells. Continuous electrochemical detection of dissolved H(2) revealed two temporally resolved phases of H(2) production during autofermentation, a minor first phase and a major second phase. The first phase was attributed to reduction of ferredoxin, because its level decreased 2-fold in nifJ cells. The second phase was attributed to glycolytic NADH production and decreased 20% in nifJ cells. Measurement of the intracellular NADH/NAD(+) ratio revealed that the reductant generated by PFOR contributing to the first phase of H(2) production was not in equilibrium with bulk NADH/NAD(+) and that the second phase corresponded to the equilibrium NADH-mediated process.
Kelsey McNeely; Yu Xu; Gennady Ananyev; Nicholas Bennette; Donald A Bryant; G Charles Dismukes
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2011-02-11
Journal Detail:
Title:  Applied and environmental microbiology     Volume:  77     ISSN:  1098-5336     ISO Abbreviation:  Appl. Environ. Microbiol.     Publication Date:  2011 Apr 
Date Detail:
Created Date:  2011-03-23     Completed Date:  2011-07-18     Revised Date:  2013-06-30    
Medline Journal Info:
Nlm Unique ID:  7605801     Medline TA:  Appl Environ Microbiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2435-44     Citation Subset:  IM    
Waksman Institute and Department of Chemistry & Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, USA.
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MeSH Terms
Acetates / metabolism
Gene Knockout Techniques
Hydrogen / metabolism
Lactic Acid / metabolism
NAD / metabolism
Pyruvate Synthase / deficiency*,  genetics
Pyruvic Acid / metabolism
Synechococcus / enzymology*,  genetics,  growth & development
Reg. No./Substance:
0/Acetates; 127-17-3/Pyruvic Acid; 1333-74-0/Hydrogen; 50-21-5/Lactic Acid; 53-84-9/NAD; EC Synthase

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