Enhanced Nitrogen Fixation in a
 Rhizobium etli ntrC
 Mutant That Overproduces the
 Bradyrhizobium japonicum
 Symbiotic Terminal Oxidase
 cbb
 3

Soberón, Mário; López, Oswaldo; Morera, Claudia; Girard, M.; Tabche, Marı́a Luisa; Miranda, J.

doi:10.1128/aem.65.5.2015-2019.1999

Cited by 23 publications

(3 citation statements)

References 26 publications

(37 reference statements)

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“…To identify NorC protein, we also included in these experiments the R. etli norC mutant. As shown in Figure 5, a 32- and 27-kDa c -type cytochromes, identified previously as the FixP and FixO subunits of the terminal oxygen high-affinity cbb 3 -type cytochrome oxidase (Soberon et al, 1999) were observed in all strains. A third band of about 17 kDa which was observed in WT cells grown with NO 3 − could not be detected in membranes from the norC mutant cultured under the same conditions (Figure 5, lanes 2 and 3).…”

Section: Resultssupporting

confidence: 60%

Rhizobium etli Produces Nitrous Oxide by Coupling the Assimilatory and Denitrification Pathways

et al. 2019

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More than two-thirds of the powerful greenhouse gas nitrous oxide (N 2 O) emissions from soils can be attributed to microbial denitrification and nitrification processes. Bacterial denitrification reactions are catalyzed by the periplasmic (Nap) or membrane-bound (Nar) nitrate reductases, nitrite reductases (NirK/ cd 1 Nir), nitric oxide reductases (cNor, qNor/ Cu A Nor), and nitrous oxide reductase (Nos) encoded by nap / nar , nir , nor and nos genes, respectively. Rhizobium etli CFN42, the microsymbiont of common bean, is unable to respire nitrate under anoxic conditions and to perform a complete denitrification pathway. This bacterium lacks the nap , nar and nos genes but contains genes encoding NirK and cNor. In this work, we demonstrated that R. etli is able to grow with nitrate as the sole nitrogen source under aerobic and microoxic conditions. Genetic and functional characterization of a gene located in the R. etli chromosome and annotated as narB demonstrated that growth under aerobic or microoxic conditions with nitrate as nitrogen source as well as nitrate reductase activity requires NarB. In addition to be involved in nitrate assimilation, NarB is also required for NO and N 2 O production by NirK and cNor, respectively, in cells grown microoxically with nitrate as the only N source. Furthermore, β-glucuronidase activity from nirK::uidA and norC::uidA fusions, as well as NorC expression and Nir and Nor activities revealed that expression of nor genes under microoxic conditions also depends on nitrate reduction by NarB. Our results suggest that nitrite produced by NarB from assimilatory nitrate reduction is detoxified by NirK and cNor denitrifying enzymes that convert nitrite into NO which in turn is reduced to N 2 O, respectively.

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Section: Resultssupporting

confidence: 60%

Rhizobium etli Produces Nitrous Oxide by Coupling the Assimilatory and Denitrification Pathways

et al. 2019

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“…has been isolated in biofilm in dental waterline tubing [ 40 ], but not found to be related to any human diseases. These are symbiotic nitrogen fixers that can be found in the roots of plants [ 41 ] and they were identified with a similarity of 96–98%. The betaproteobacterial Delftia tsuruhatensis (96% similarity) is a terephthalate-assimilating bacterium [ 42 ] and Diaphorobacter sp.…”

Section: Discussionmentioning

confidence: 99%

Use of cultivation-dependent and -independent techniques to assess contamination of central venous catheters: a pilot study

et al. 2008

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BackgroundCatheters are the most common cause of nosocomial infections and are associated with increased risk of mortality, length of hospital stay and cost. Prevention of infections and fast and correct diagnosis is highly important.MethodsIn this study traditional semiquantitative culture-dependent methods for diagnosis of bacteria involved in central venous catheter-related infections as described by Maki were compared with the following culture-independent molecular biological methods: Clone libraries, denaturant gradient gel electrophoresis, phylogeny and fluorescence in situ hybridization.ResultsIn accordance with previous studies, the cultivation of central venous catheters from 18 patients revealed that S. epidermidis and other coagulase-negative staphylococci were most abundant and that a few other microorganisms such as P. aeruginosa and K. pneumoniae occasionally were found on the catheters. The molecular analysis using clone libraries and sequencing, denaturant gradient gel electrophoresis and sequencing provided several important results. The species found by cultivation were confirmed by molecular methods. However, many other bacteria belonging to the phyla Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes were also found, stressing that only a minor portion of the species present were found by cultivation. Some of these bacteria are known to be pathogens, some have not before been described in relation to human health, and some were not closely related to known pathogens and may represent new pathogenic species. Furthermore, there was a clear difference between the bacterial species found in biofilm on the external (exluminal) and internal (luminal) side of the central venous catheter, which can not be detected by Maki's method. Polymicrobial biofilms were observed on most of the catheters and were much more common than the cultivation-dependent methods indicated.ConclusionThe results show that diagnosis based on molecular methods improves the detection of microorganisms involved in central catheter-related infections. The importance of these microorganisms needs to be investigated further, also in relation to contamination risk from improper catheter handling, as only in vivo contaminants are of interest. This information can be used for development of fast and more reliable diagnostic tools, which can be used in combination with traditional methods.

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“…The inoculation of P. vulgaris plants with a R. etli strain having enhanced expression of cbb3 oxidase in bacteroids reduced the sensitivity of P. vulgaris-R. etli symbiosis to drought [113]. Others studies have also reported that genetically modified rhizobial strains overproducing cbb3 oxidase are more efficient in nitrogen fixation under optimal conditions compared to their parental strains [114],[115].…”

Section: Rhizobia Improvement Using Stress Response Genesmentioning

confidence: 99%

Can stress response genes be used to improve the symbiotic performance of rhizobia?

2017

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Rhizobia are soil bacteria able to form symbioses with legumes and fix atmospheric nitrogen, converting it into a form that can be assimilated by the plant. The biological nitrogen fixation is a possible strategy to reduce the environmental pollution caused by the use of chemical N-fertilizers in agricultural fields. Successful colonization of the host root by free-living rhizobia requires that these bacteria are able to deal with adverse conditions in the soil, in addition to stresses that may occur in their endosymbiotic life inside the root nodules. Stress response genes, such as otsAB , groEL , clpB , rpoH play an important role in tolerance of free-living rhizobia to different environmental conditions and some of these genes have been shown to be involved in the symbiosis. This review will focus on stress response genes that have been reported to improve the symbiotic performance of rhizobia with their host plants. For example, chickpea plants inoculated with a Mesorhizobium strain modified with extra copies of the groEL gene showed a symbiotic effectiveness approximately 1.5 fold higher than plants inoculated with the wild-type strain. Despite these promising results, more studies are required to obtain highly efficient and tolerant rhizobia strains, suitable for different edaphoclimatic conditions, to be used as field inoculants.

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Enhanced Nitrogen Fixation in a Rhizobium etli ntrC Mutant That Overproduces the Bradyrhizobium japonicum Symbiotic Terminal Oxidase cbb ₃

Cited by 23 publications

References 26 publications

Rhizobium etli Produces Nitrous Oxide by Coupling the Assimilatory and Denitrification Pathways

Rhizobium etli Produces Nitrous Oxide by Coupling the Assimilatory and Denitrification Pathways

Use of cultivation-dependent and -independent techniques to assess contamination of central venous catheters: a pilot study

Can stress response genes be used to improve the symbiotic performance of rhizobia?

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Enhanced Nitrogen Fixation in a Rhizobium etli ntrC Mutant That Overproduces the Bradyrhizobium japonicum Symbiotic Terminal Oxidase cbb 3

Cited by 23 publications

References 26 publications

Rhizobium etli Produces Nitrous Oxide by Coupling the Assimilatory and Denitrification Pathways

Rhizobium etli Produces Nitrous Oxide by Coupling the Assimilatory and Denitrification Pathways

Use of cultivation-dependent and -independent techniques to assess contamination of central venous catheters: a pilot study

Can stress response genes be used to improve the symbiotic performance of rhizobia?

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Enhanced Nitrogen Fixation in a Rhizobium etli ntrC Mutant That Overproduces the Bradyrhizobium japonicum Symbiotic Terminal Oxidase cbb ₃