scholarly journals An integrated biochemical system for nitrate assimilation and nitric oxide detoxification in Bradyrhizobium japonicum

2016 ◽  
Vol 473 (3) ◽  
pp. 297-309 ◽  
Author(s):  
Juan J. Cabrera ◽  
Ana Salas ◽  
María J. Torres ◽  
Eulogio J. Bedmar ◽  
David J. Richardson ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Bradyrhizobium Japonicum ◽  
Nitrate Assimilation ◽  
Functional System ◽  
Biochemical System ◽  
Dual Functional ◽  
Detoxification System ◽  
Nitric Oxide Detoxification ◽  
Dependent Growth

We report a dual functional system for bacterial nitrate (NO3−) assimilation and nitric oxide (NO) detoxification. The assimilatory NO3− reductase (NasC) can generate nitric oxide (NO). Co-expression of an NO-detoxification system acts to counteract accumulation of cytotoxic NO during anaerobic NO3−-dependent growth.

The role of Bradyrhizobium japonicum nitric oxide reductase in nitric oxide detoxification in soya bean root nodules

2006 ◽  
Vol 34 (1) ◽  
pp. 195-196 ◽  
Author(s):  
G.E. Meakin ◽  
B.J.N. Jepson ◽  
D.J. Richardson ◽  
E.J. Bedmar ◽  
M.J. Delgado
Keyword(s):  
Nitric Oxide ◽  
Bradyrhizobium Japonicum ◽  
Root Nodules ◽  
Soya Bean ◽  
Nitric Oxide Reductase ◽  
Bean Root ◽  
Detoxification Systems ◽  
Nitric Oxide Detoxification

The identification of nitric oxide-bound leghaemoglobin within soya bean nodules has led to the question of how Bradyrhizobium japonicum bacteroids overcome the toxicity of this nitric oxide. It has previously been shown that one candidate for nitric oxide detoxification, the respiratory nitric oxide reductase, is expressed in soya bean nodules from plants supplied with nitrate [Mesa, de Dios Alché, Bedmar and Delgado (2004) Physiol. Plant. 120, 205–211]. In this paper, the role of this enzyme in nitric oxide detoxification is assessed and discussion is provided on other possible B. japonicum nitric oxide detoxification systems.

The complete denitrification pathway of the symbiotic, nitrogen-fixing bacterium Bradyrhizobium japonicum

2005 ◽  
Vol 33 (1) ◽  
pp. 141-144 ◽  
Author(s):  
E.J. Bedmar ◽  
E.F. Robles ◽  
M.J. Delgado
Keyword(s):  
Nitric Oxide ◽  
Nitrous Oxide ◽  
Bradyrhizobium Japonicum ◽  
Mutational Analysis ◽  
Control Level ◽  
Gene Clusters ◽  
Alternative Form ◽  
Nitrate Respiration ◽  
Regulatory Cascade ◽  
Denitrification Genes

Denitrification is an alternative form of respiration in which bacteria sequentially reduce nitrate or nitrite to nitrogen gas by the intermediates nitric oxide and nitrous oxide when oxygen concentrations are limiting. In Bradyrhizobium japonicum, the N2-fixing microsymbiont of soya beans, denitrification depends on the napEDABC, nirK, norCBQD, and nosRZDFYLX gene clusters encoding nitrate-, nitrite-, nitric oxide- and nitrous oxide-reductase respectively. Mutational analysis of the B. japonicum nap genes has demonstrated that the periplasmic nitrate reductase is the only enzyme responsible for nitrate respiration in this bacterium. Regulatory studies using transcriptional lacZ fusions to the nirK, norCBQD and nosRZDFYLX promoter region indicated that microaerobic induction of these promoters is dependent on the fixLJ and fixK2 genes whose products form the FixLJ–FixK2 regulatory cascade. Besides FixK2, another protein, nitrite and nitric oxide respiratory regulator, has been shown to be required for N-oxide regulation of the B. japonicum nirK and norCBQD genes. Thus nitrite and nitric oxide respiratory regulator adds to the FixLJ–FixK2 cascade an additional control level which integrates the N-oxide signal that is critical for maximal induction of the B. japonicum denitrification genes. However, the identity of the signalling molecule and the sensing mechanism remains unknown.

scholarly journals Interplay of Nitric Oxide Synthase (NOS) and SrrAB in Modulation ofStaphylococcus aureusMetabolism and Virulence

2018 ◽  
Vol 87 (2) ◽  
Author(s):  
Kimberly L. James ◽  
Austin B. Mogen ◽  
Jessica N. Brandwein ◽  
Silvia S. Orsini ◽  
Miranda J. Ridder ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Double Mutant ◽  
Nitrate Assimilation ◽  
Arginine Deiminase ◽  
Growth Defect ◽  
Content Type ◽  
Metabolic Versatility ◽  
Oxide Synthase

ABSTRACTStaphylococcus aureusnitric oxide synthase (saNOS) is a major contributor to virulence, stress resistance, and physiology, yet the specific mechanism(s) by which saNOS intersects with other known regulatory circuits is largely unknown. The SrrAB two-component system, which modulates gene expression in response to the reduced state of respiratory menaquinones, is a positive regulator ofnosexpression. Several SrrAB-regulated genes were also previously shown to be induced in an aerobically respiringnosmutant, suggesting a potential interplay between saNOS and SrrAB. Therefore, a combination of genetic, molecular, and physiological approaches was employed to characterize anos srrABmutant, which had significant reductions in the maximum specific growth rate and oxygen consumption when cultured under conditions promoting aerobic respiration. Thenos srrABmutant secreted elevated lactate levels, correlating with the increased transcription of lactate dehydrogenases. Expression of nitrate and nitrite reductase genes was also significantly enhanced in thenos srrABdouble mutant, and its aerobic growth defect could be partially rescued with supplementation with nitrate, nitrite, or ammonia. Furthermore, elevated ornithine and citrulline levels and highly upregulated expression of arginine deiminase genes were observed in the double mutant. These data suggest that a dual deficiency in saNOS and SrrAB limitsS. aureusto fermentative metabolism, with a reliance on nitrate assimilation and the urea cycle to help fuel energy production. Thenos,srrAB, andnos srrABmutants showed comparable defects in endothelial intracellular survival, whereas thesrrABandnos srrABmutants were highly attenuated during murine sepsis, suggesting that SrrAB-mediated metabolic versatility is dominantin vivo.

Sign in / Sign up

Export Citation Format

Share Document