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Examining the Effects of the Nitrogen Environment on Growth and N 2-Fixation of Endophytic Herbaspirillum seropedicae in Maize Seedlings by Applying 11C Radiotracing. Microorganisms 2021; 9:microorganisms9081582. [PMID: 34442661 PMCID: PMC8401641 DOI: 10.3390/microorganisms9081582] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 07/15/2021] [Accepted: 07/23/2021] [Indexed: 11/17/2022] Open
Abstract
Herbaspirillum seropedicae, as an endophyte and prolific root colonizer of numerous cereal crops, occupies an important ecological niche in agriculture because of its ability to promote plant growth and potentially improve crop yield. More importantly, there exists the untapped potential to harness its ability, as a diazotroph, to fix atmospheric N2 as an alternative nitrogen resource to synthetic fertilizers. While mechanisms for plant growth promotion remain controversial, especially in cereal crops, one irrefutable fact is these microorganisms rely heavily on plant-borne carbon as their main energy source in support of their own growth and biological functions. Biological nitrogen fixation (BNF), a microbial function that is reliant on nitrogenase enzyme activity, is extremely sensitive to the localized nitrogen environment of the microorganism. However, whether internal root colonization can serve to shield the microorganisms and de-sensitize nitrogenase activity to changes in the soil nitrogen status remains unanswered. We used RAM10, a GFP-reporting strain of H. seropedicae, and administered radioactive 11CO2 tracer to intact 3-week-old maize leaves and followed 11C-photosynthates to sites within intact roots where actively fluorescing microbial colonies assimilated the tracer. We examined the influence of administering either 1 mM or 10 mM nitrate during plant growth on microbial demands for plant-borne 11C. Nitrogenase activity was also examined under the same growth conditions using the acetylene reduction assay. We found that plant growth under low nitrate resulted in higher nitrogenase activity as well as higher microbial demands for plant-borne carbon than plant growth under high nitrate. However, carbon availability was significantly diminished under low nitrate growth due to reduced host CO2 fixation and reduced allocation of carbon resources to the roots. This response of the host caused significant inhibition of microbial growth. In summary, internal root colonization did little to shield these endophytic microorganisms from the nitrogen environment.
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Van Oosten MJ, Di Stasio E, Cirillo V, Silletti S, Ventorino V, Pepe O, Raimondi G, Maggio A. Root inoculation with Azotobacter chroococcum 76A enhances tomato plants adaptation to salt stress under low N conditions. BMC PLANT BIOLOGY 2018; 18:205. [PMID: 30236058 PMCID: PMC6149061 DOI: 10.1186/s12870-018-1411-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 08/31/2018] [Indexed: 05/20/2023]
Abstract
BACKGROUND The emerging roles of rhizobacteria in improving plant nutrition and stress protection have great potential for sustainable use in saline soils. We evaluated the function of the salt-tolerant strain Azotobacter chroococcum 76A as stress protectant in an important horticultural crop, tomato. Specifically we hypothesized that treatment of tomato plants with A. chroococcum 76A could improve plant performance under salinity stress and sub-optimal nutrient regimen. RESULTS Inoculation of Micro Tom tomato plants with A. chroococcum 76A increased numerous growth parameters and also conferred protective effects under both moderate (50 mM NaCl) and severe (100 mM NaCl) salt stresses. These benefits were mostly observed under reduced nutrient regimen and were less appreciable in optimal nitrogen conditions. Therefore, the efficiency of A. chroococcum 76A was found to be dependent on the nutrient status of the rhizosphere. The expression profiles of LEA genes indicated that A. chroococcum 76A treated plants were more responsive to stress stimuli when compared to untreated controls. However, transcript levels of key nitrogen assimilation genes revealed that the optimal nitrogen regimen, in combination with the strain A. chroococcum 76A, may have saturated plant's ability to assimilate nitrogen. CONCLUSIONS Roots inoculation with A. chroococcum 76A tomato promoted tomato plant growth, stress tolerance and nutrient assimilation efficiency under moderate and severe salinity. Inoculation with beneficial bacteria such as A. chroococcum 76A may be an ideal solution for low-input systems, where environmental constraints and limited chemical fertilization may affect the potential yield.
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Affiliation(s)
- Michael James Van Oosten
- Department of Agricultural Sciences, University of Naples Federico II, Via Università, 100, Portici, Italy
| | - Emilio Di Stasio
- Department of Agricultural Sciences, University of Naples Federico II, Via Università, 100, Portici, Italy
| | - Valerio Cirillo
- Department of Agricultural Sciences, University of Naples Federico II, Via Università, 100, Portici, Italy
| | - Silvia Silletti
- Department of Agricultural Sciences, University of Naples Federico II, Via Università, 100, Portici, Italy
| | - Valeria Ventorino
- Department of Agricultural Sciences, University of Naples Federico II, Via Università, 100, Portici, Italy
| | - Olimpia Pepe
- Department of Agricultural Sciences, University of Naples Federico II, Via Università, 100, Portici, Italy
| | - Giampaolo Raimondi
- Department of Agricultural Sciences, University of Naples Federico II, Via Università, 100, Portici, Italy
| | - Albino Maggio
- Department of Agricultural Sciences, University of Naples Federico II, Via Università, 100, Portici, Italy.
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Juraeva D, George E, Davranov K, Ruppel S. Detection and quantification of the nifH gene in shoot and root of cucumber plants. Can J Microbiol 2006; 52:731-9. [PMID: 16917531 DOI: 10.1139/w06-025] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A real-time polymerase chain reaction (PCR) method was applied to quantify the nifH gene pool in cucumber shoot and root and to evaluate how nitrogen (N) supply and plant age affect the nifH gene pool. In shoots, the relative abundance of the nifH gene was affected neither by different stages of plant growth nor by N supply. In roots, higher numbers of diazotrophic bacteria were found compared with that in the shoot. The nifH gene pool in roots significantly increased with plant age, and unexpectedly, the pool size was positively correlated with N supply. The relative abundance of nifH gene copy numbers in roots was also positively correlated (r = 0.96) with total N uptake of the plant. The data suggest that real-time PCR-based nifH gene quantification in combination with N-content analysis can be used as an efficient way to perform further studies to evaluate the direct contribution of the N2-fixing plant-colonizing plant growth promoting bacteria to plant N nutrition.Key words: real-time PCR, biological nitrogen fixation, cucumber, N nutrition, plant growth promoting bacteria.
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Affiliation(s)
- Dilafruz Juraeva
- Department of Plant Nutrition, Institute of Vegetable and Ornamental Crops, Theodor-Echtermeyer Weg 1, 14979 Grossbeeren, Germany.
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Ruiz M, Cejudo F, Muñoz-Centeno M, Paneque A. Isolation and characterization of an Azotobacter chroococcum mutant deficient in nitrate transport. FEMS Microbiol Lett 2006. [DOI: 10.1111/j.1574-6968.1990.tb13865.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Poly F, Ranjard L, Nazaret S, Gourbière F, Monrozier LJ. Comparison of nifH gene pools in soils and soil microenvironments with contrasting properties. Appl Environ Microbiol 2001; 67:2255-62. [PMID: 11319109 PMCID: PMC92864 DOI: 10.1128/aem.67.5.2255-2262.2001] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The similarities and differences in the structures of the nifH gene pools of six different soils (Montrond, LCSA-p, Vernon, Dombes, LCSA-c, and Thysse Kaymor) and five soil fractions extracted from LCSA-c were studied. Bacterial DNA was directly extracted from the soils, and a region of the nifH gene was amplified by PCR and analyzed by restriction. Soils were selected on the basis of differences in soil management, plant cover, and major physicochemical properties. Microenvironments differed on the basis of the sizes of the constituent particles and the organic carbon and clay contents. Restriction profiles were subjected to principal-component analysis. We showed that the composition of the diazotrophic communities varied both on a large scale (among soils) and on a microscale (among microenvironments in LCSA-c soil). Soil management seemed to be the major parameter influencing differences in the nifH gene pool structure among soils by controlling inorganic nitrogen content and its variation. However, physicochemical parameters (texture and total C and N contents) were found to correlate with differences among nifH gene pools on a microscale. We hypothesize that the observed nifH genetic structures resulted from the adaptation to fluctuating conditions (cultivated soil, forest soil, coarse fractions) or constant conditions (permanent pasture soil, fine fractions). We attempted to identify a specific band within the profile of the clay fraction by cloning and sequencing it and comparing it with the gene databases. Unexpectedly, the nifH sequences of the dominant bacteria were most similar to sequences of unidentified marine eubacteria.
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Affiliation(s)
- F Poly
- UMR CNRS 5557 Ecologie Microbienne, Université Claude Bernard Lyon 1, 43 Bd. 11 Novembre 1918, 69622 Villeurbanne Cedex, France.
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Muñoz-Centeno MC, Peciña A, Cejudo FJ, Paneque A. A sensor protein involved in induction of nitrate assimilation in Azotobacter chroococcum. FEBS Lett 1996; 393:7-12. [PMID: 8804413 DOI: 10.1016/0014-5793(96)00843-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Nitrogen-fixing Azotobacter chroococcum cells, but not ammonium- or nitrate-grown cells, exhibited two polypeptide components of 22 and 35 kDa, respectively, that we termed P22 and P35. Bidimensional polyacrylamide gel electrophoresis analysis of preparations from N2-fixing cells that had been transferred to nitrate medium and then incubated for 2 h revealed that P22 had shifted to a more acidic part of the gel while P35 did not change its electrophoretic pattern. Using [32P]orthophosphoric acid it could be demonstrated that the shift in mobility of P22 was due to the phosphorylation of the polypeptide dependent on nitrate (nitrite). The A. chroococcum TR1 strain, which is unable to use nitrate as a nitrogen source and displays activities of nitrogenase, nitrate reductase and nitrite reductase, exhibited both polypeptides. In contrast, P22 and P35 were absent from A. chroococcum MCD1, a mutant strain that cannot assimilate nitrate and lacks the nitrate-reducing enzymatic system. The results suggest that P22 could act as a sensor protein for nitrate in A. chroococcum.
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Affiliation(s)
- M C Muñoz-Centeno
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-Consejo Superior de Investigaciones Científicas, Spain
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Muñoz-Centeno MC, Ruiz MT, Paneque A, Cejudo FJ. Posttranslational regulation of nitrogenase activity by fixed nitrogen in Azotobacter chroococcum. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1291:67-74. [PMID: 8781527 DOI: 10.1016/0304-4165(96)00045-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Using anti-(Fe protein) antibody raised against the Fe protein of the photosynthetic bacterium Rhodospirillum rubrum, it was found that the Fe protein component of nitrogenase (EC 1.18.2.1) from Azotobacter chroococcum cells subjected to an ammonium shock, and hence with an inactive nitrogenase, appeared as a doublet in Western blot analysis of cell extracts. The Fe protein incorporated [32P]phosphate and [3H]adenine in response to ammonium treatment, and L-methionine-DL-sulfoximine, an inhibitor of glutamine synthetase (L-glutamate: ammonia ligase (ADP forming), EC 6.3.1.2), prevented Fe protein from inhibition and radioisotope labelling. These results support that A. chroococcum Fe protein is most likely ADP-ribosylated in response to ammonium. After ammonium treatment, when in vivo activity was completely inhibited, Fe-protein modification was still increasing. This suggests the existence of another mechanism of nitrogenase inhibition faster than Fe-protein modification. When ammonium was intracellularly generated instead of being externally added, as occurs with the short-term nitrate inhibition of nitrogenase activity observed in A. chroococcum cells simultaneously fixing molecular nitrogen and assimilating nitrate, a covalent modification of the Fe protein was likewise demonstrated.
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Affiliation(s)
- M C Muñoz-Centeno
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-Consejo Superior de Investigaciones Científicas, Facultad de Biología, Spain
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Muñoz-Centeno MC, Cejudo FJ, Paneque A. In vivo modification of Azotobacter chroococcum glutamine synthetase. Biochem J 1994; 298 Pt 3:641-5. [PMID: 7908189 PMCID: PMC1137908 DOI: 10.1042/bj2980641] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A monospecific anti-(glutamine synthetase) antibody raised against glutamine synthetase of the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 immunoreacted with glutamine synthetase from the N2-fixing heterotrophic bacterium Azotobacter chroococcum. In Western-blotting experiments this antibody recognized a single protein of a molecular mass of 59 kDa corresponding to glutamine synthetase subunit. This protein was in vivo-labelled in response to addition of ammonium, both [3H]adenine and H(3)32PO4 preincubation of the cells being equally effective. Nevertheless, the amount of glutamine synthetase present in A. chroococcum was independent of the available nitrogen source. Modified, inactive glutamine synthetase was re-activated by treatment with snake-venom phosphodiesterase but not by alkaline phosphatase. L-Methionine-DL-sulphoximine, an inhibitor of glutamine synthetase, prevented the enzyme from being covalently modified. We conclude that, in A. chroococcum, glutamine synthetase is adenylylated in response to ammonium and that for the modification to take place ammonium must be metabolized.
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Affiliation(s)
- M C Muñoz-Centeno
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-Consejo Superior de Investigaciones Científicas, Spain
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Muñoz-Centeno M, Cejudo F, Ruiz M, Paneque A. The Azotobacter chroococcum nitrate permease is a multicomponent system. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1993. [DOI: 10.1016/0005-2728(93)90191-h] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Nitrite uptake in Azotobacter chroococcum. Arch Microbiol 1992. [DOI: 10.1007/bf00276776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Purification and properties of an extracellular invertase from Azotobacter chroococcum. Enzyme Microb Technol 1991. [DOI: 10.1016/0141-0229(91)90140-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Effect of divalent cations on the short-term NH 4 + inhibition of nitrogen fixation in Azotobacter chroococcum. Arch Microbiol 1990. [DOI: 10.1007/bf00276524] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Ruiz MT, Cejudo FJ, Paneque A. Role of Mn(II) as regulator of nitrate assimilation in Azotobacter chroococcum. Biochim Biophys Acta Gen Subj 1989. [DOI: 10.1016/0304-4165(89)90139-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Effect of nitrogen starvation on ammonium-inhibition of nitrogenase activity in Azotobacter chroococcum. Arch Microbiol 1988. [DOI: 10.1007/bf00446748] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Cejudo F, Paneque A. Correlation between nitrate uptake rate and nitrate inhibition of nitrogenase activity in Azotobacter chroococcum. FEMS Microbiol Lett 1987. [DOI: 10.1111/j.1574-6968.1987.tb02088.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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