scholarly journals Genetic control of nitrate assimilation in Klebsiella oxytoca. Final technical report

2001 ◽  
Author(s):  
Valley J Stewart
Keyword(s):  
Genetic Control ◽  
Klebsiella Oxytoca ◽  
Nitrate Assimilation ◽  
Technical Report

scholarly journals Bacterial nitrate assimilation: gene distribution and regulation

2011 ◽  
Vol 39 (6) ◽  
pp. 1838-1843 ◽  
Author(s):  
Víctor M. Luque-Almagro ◽  
Andrew J. Gates ◽  
Conrado Moreno-Vivián ◽  
Stuart J. Ferguson ◽  
David J. Richardson ◽  
...  
Keyword(s):  
Rhodobacter Capsulatus ◽  
Heterotrophic Bacteria ◽  
Azotobacter Vinelandii ◽  
Klebsiella Oxytoca ◽  
Prokaryotic Genome ◽  
Nitrate Assimilation ◽  
Primary Role ◽  
Bacterial Strains ◽  
Global Nitrogen Cycle

In the context of the global nitrogen cycle, the importance of inorganic nitrate for the nutrition and growth of marine and freshwater autotrophic phytoplankton has long been recognized. In contrast, the utilization of nitrate by heterotrophic bacteria has historically received less attention because the primary role of these organisms has classically been considered to be the decomposition and mineralization of dissolved and particulate organic nitrogen. In the pre-genome sequence era, it was known that some, but not all, heterotrophic bacteria were capable of growth on nitrate as a sole nitrogen source. However, examination of currently available prokaryotic genome sequences suggests that assimilatory nitrate reductase (Nas) systems are widespread phylogenetically in bacterial and archaeal heterotrophs. Until now, regulation of nitrate assimilation has been mainly studied in cyanobacteria. In contrast, in heterotrophic bacterial strains, the study of nitrate assimilation regulation has been limited to Rhodobacter capsulatus, Klebsiella oxytoca, Azotobacter vinelandii and Bacillus subtilis. In Gram-negative bacteria, the nas genes are subjected to dual control: ammonia repression by the general nitrogen regulatory (Ntr) system and specific nitrate or nitrite induction. The Ntr system is widely distributed in bacteria, whereas the nitrate/nitrite-specific control is variable depending on the organism.

scholarly journals General Nitrogen Regulation of Nitrate Assimilation Regulatory Gene nasR Expression in Klebsiella oxytoca M5al

1999 ◽  
Vol 181 (23) ◽  
pp. 7274-7284 ◽  
Author(s):  
Stephen Qitu Wu ◽  
Weihang Chai ◽  
Janine T. Lin ◽  
Valley Stewart
Keyword(s):  
Gene Expression ◽  
Transcription Initiation ◽  
Regulatory Gene ◽  
Klebsiella Oxytoca ◽  
Nitrate Assimilation ◽  
Single Copy ◽  
Initiation Site ◽  
Nitrogen Regulation ◽  
Transcription Activator ◽  
Nitrate And Nitrite

ABSTRACT Klebsiella oxytoca can assimilate nitrate and nitrite by using enzymes encoded by the nasFEDCBA operon. Expression of the nasF operon is controlled by general nitrogen regulation (Ntr) via the NtrC transcription activator and by pathway-specific nitrate and nitrite induction via the NasR transcription antiterminator. This paper reports our analysis ofnasR gene expression. We constructed strains bearing single-copy Φ(nasR-lacZ) operon fusions within the chromosomal rhaBAD-rhaSR locus. The expression of ΔrhaBS::[Φ(nasR-lacZ)] operon fusions was induced about 10-fold during nitrogen-limited growth. Induction was reduced in both ntrC and rpoNnull mutants, indicating that Ntr control of nasR gene expression requires the NtrC and ςN (ς54) proteins. Sequence inspection of the nasR control region reveals an apparent ςN-dependent promoter but no apparent NtrC protein binding sites. Analysis of site-specific mutations coupled with primer extension analysis authenticated the ςN-dependent nasR promoter. Fusion constructs with only about 70 nucleotides (nt) upstream of the transcription initiation site exhibited patterns of β-galactosidase expression indistinguishable from Φ(nasR-lacZ) constructs with about 470 nt upstream. Expression was independent of the Nac protein, implying that NtrC is a direct activator of nasRtranscription. Together, these results indicate that nasRgene expression does not require specific upstream NtrC-binding sequences, as previously noted for argT gene expression inSalmonella typhimurium (G. Schmitz, K. Nikaido, and G. F.-L. Ames, Mol. Gen. Genet. 215:107–117, 1988).

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