Spontaneous Mutations in the Nitrate Reductase Gene napC Drive the Emergence of Eco-friendly Low-N2O-Emitting Alfalfa Rhizobia in Regions with Different Climates

Brambilla, Silvina; Soto, Gabriela; Odorizzi, Ariel; Arolfo, Valeria; McCormick, Wayne; Primo, Emiliano David; Giordano, Walter; Jozefkowicz, Cintia; Ayub, Nicolás Daniel

doi:10.1007/s00248-019-01473-w

Cited by 12 publications

(4 citation statements)

References 27 publications

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“…The genome sequence revealed the presence of the napEFDABC, nirK, norECBQD and nosRZDFYLX denitrification genes (Torres et al, 2014). As such, it is possible to speculate that the N 2 O emission of this strain could be comparable to the levels of strain 1021, which are significantly lower than strain B399 (Brambilla et al, 2020).…”

Section: Denitrification Pathwaymentioning

confidence: 88%

“…Particularly, the use of S. meliloti strains that have the nap-nir-nor gene cluster, which can start the denitrification process, but lack the nos gene cluster (involved in the last step of this pathway, converting the greenhouse N 2 O into the inert N 2 ) is not desirable. This is the case of the S. meliloti B399 strain, extensively used for decades in Argentina as alfalfa inoculant, which has recently been shown to produce high levels of N 2 O during symbiosis (Brambilla et al, 2020). We were therefore interested in determining the integrity of the denitrification pathway in strain LPU63.…”

Section: Denitrification Pathwaymentioning

confidence: 99%

“…Recently, a novel strategy to avoid these undesirable metabolic pathways was the screening of S. meliloti strains with spontaneous mutations in napC, which encodes the nitrate reductase structural protein NapC involved in the first step of N 2 O production via the denitrification process. These napC minus strains are consequently unable to start the denitrification pathway (Brambilla et al, 2020). While these strains are regarded as eco-friendly, due to the extremely low N 2 O production in the symbiosis with alfalfa, it remains to be proven whether they are able to survive in field conditions, especially when O 2 is limited.…”

Section: Denitrification Pathwaymentioning

confidence: 99%

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Genomic analysis of Sinorhizobium meliloti LPU63, an acid-tolerant and symbiotically efficient alfalfa-nodulating rhizobia

Cafiero¹,

Casasco²,

Lozano³

et al. 2023

Front. Agron.

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The growth and persistence of alfalfa (Medicago sativa), a perennial legume capable of producing high yields of high-quality forage, is reduced in moderately acidic soils. The low performance of alfalfa at low pH is due to numerous factors that affect the host plant, their rhizobia, and the symbiotic interaction. Sinorhizobium meliloti LPU63 was isolated from acid topsoil (in Argentina) and showed to be a highly competitive and efficient N2-fixing rhizobium under both neutral and moderately acidic soil conditions. In this study, we obtained a draft of the LPU63 genome sequence using Illumina HiSeq4000. The whole genome phylogenetic analysis confirmed the taxonomic position of LPU63 as a S. meliloti strain and the multilocus sequence analysis confirmed that LPU63 is not related to the strains used in Argentina in bioformulations. The genomic analysis showed that beyond the canonical chromosome, pSymA, and pSymB, LPU63 strain has an accessory plasmid that codes for a repABC origin of replication and a conjugative T4SS, suggesting that this plasmid could be self-transmissible. In addition, the complete denitrification pathway (i.e., the gene clusters nap, nir, nor, and nos), including napC and nosZ, which could be used as an alternative respiration route under hypoxic conditions with moderate N2O emissions was found. Also, genes associated with plant growth-promoting activities (PGPR) and the degradation of phenylacetic acid (PAA) were identified. LPU63 is a highly melanogenic strain, a property that could enhance its survival under soil conditions, and the genome data showed a particular arrangement of the genes involved in melanin production. The information regarding LPU63 activities compatible with plant-growth promotion phenotypes, together with other characteristics mentioned here (melanin production, potential moderate N2O emissions), constitute the basis of future experiments toward the rational design of a novel bioinoculant for the environmentally sustainable production of alfalfa.

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Section: Denitrification Pathwaymentioning

confidence: 88%

Section: Denitrification Pathwaymentioning

confidence: 99%

Section: Denitrification Pathwaymentioning

confidence: 99%

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Genomic analysis of Sinorhizobium meliloti LPU63, an acid-tolerant and symbiotically efficient alfalfa-nodulating rhizobia

Cafiero¹,

Casasco²,

Lozano³

et al. 2023

Front. Agron.

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“…Center (Baba et al, 2006), were used in this study. The integrity of the glnKamtB operon in strain BW25113 and the knockout of this operon by the insertion of a kanamycin cassette in strain JW0441 were verified by sequencing and analyzing their genomes by means of Illumina Hiseq1500 technology and Geneious as indicated previously (Brambilla et al, 2019).…”

Section: Bacterial Strains and Genomic Analysesmentioning

confidence: 99%

Elimination of GlnKAmtB affects serine biosynthesis and improves growth and stress tolerance of Escherichia coli under nutrient-rich conditions

Frare

Stritzler

Pascuan

et al. 2020

FEMS Microbiology Letters

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Nitrogen is a most important nutrient resource for Escherichia coli and other bacteria that harbor the glnKamtB operon, a high-affinity ammonium uptake system highly interconnected with cellular metabolism. Although this system confers an advantage to bacteria when growing under nitrogen-limiting conditions, little is known about the impact of these genes on microbial fitness under nutrient-rich conditions. Here, the genetically tractable E. coli BW25113 strain and its glnKamtB-null mutant (JW0441) were used to analyze the impact of GlnK-AmtB on growth rates and oxidative stress tolerance. Strain JW0441 showed a shorter initial lag phase, higher growth rate, higher citrate synthase activity, higher oxidative stress tolerance and lower expression of serA than strain BW25113 under nutrient-rich conditions, suggesting a fitness cost to increase metabolic plasticity associated with serine metabolism. The overexpression of serA in strain JW0441 resulted in a decreased growth rate and stress tolerance in nutrient-rich conditions similar to that of strain BW25113, suggesting that the negative influence on bacterial fitness imposed by GlnK-AmtB can be traced to the control of serine biosynthesis. Finally, we discuss the potential applications of glnKamtB mutants in bioproduction processes.

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Exploring the Role of the NO-Detoxifying Enzyme HmpA in the Evolution of Domesticated Alfalfa Rhizobia

et al. 2021

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Spontaneous Mutations in the Nitrate Reductase Gene napC Drive the Emergence of Eco-friendly Low-N2O-Emitting Alfalfa Rhizobia in Regions with Different Climates

Cited by 12 publications

References 27 publications

Genomic analysis of Sinorhizobium meliloti LPU63, an acid-tolerant and symbiotically efficient alfalfa-nodulating rhizobia

Genomic analysis of Sinorhizobium meliloti LPU63, an acid-tolerant and symbiotically efficient alfalfa-nodulating rhizobia

Elimination of GlnKAmtB affects serine biosynthesis and improves growth and stress tolerance of Escherichia coli under nutrient-rich conditions

Exploring the Role of the NO-Detoxifying Enzyme HmpA in the Evolution of Domesticated Alfalfa Rhizobia

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