RESUMEN
In the face of agricultural challenges posed by both abiotic and biotic stressors, phytopathogens emerge as formidable threats to crop productivity. Conventional methods, involving the use of pesticides and microbes, often lead to unintended consequences. In addressing this issue, ICAR -Indian Institute of Oilseeds Research (ICAR-IIOR) has developed a chitosan-based double-layer seed coating. Emphasizing crop input compatibility, entrapment, and characterization, the study has yielded promising results. The double-layer coating on groundnut seeds enhanced germination and seedling vigor. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) confirmed the structural changes and entrapment of crop inputs. The persistence of T. harzianum (Th4d) and Bradyrhizobium sp. in chitosan blended film in studied soils revealed that viable propogules of Th4d were recorded in double layer treatment combination with 3.54 and 3.50 Log CFUs/g of soil (colony forming units) and Bradyrhizobium sp. with 5.34 and 5.27 Log CFUs/g of soil at 90 days after application (DAA). Root colonization efficacy studies of Th4d and Bradyrhizobium sp. in groundnut crop in studied soils revealed that, maximum viable colonies were observed at 45 days after sowing (DAS). This comprehensive study highlights the potential of chitosan-based double-layer seed coating providing a promising and sustainable strategy for stress management in agriculture.
Asunto(s)
Bradyrhizobium , Quitosano , Semillas , Estrés Fisiológico , Quitosano/química , Quitosano/farmacología , Semillas/efectos de los fármacos , Bradyrhizobium/efectos de los fármacos , Bradyrhizobium/fisiología , Estrés Fisiológico/efectos de los fármacos , Germinación/efectos de los fármacos , Plantones/efectos de los fármacos , Plantones/crecimiento & desarrollo , Vigna/efectos de los fármacos , Vigna/crecimiento & desarrolloRESUMEN
Microplastics (MPs), widely presented in cultivated soil, have caused serious stresses on crop growth. However, the mechanism by which MPs affect legumes and rhizobia symbiosis is still unclear. Here, peanut seedlings were inoculated with Bradyrhizobium zhanjiangense CCBAU 51778 and were grown in vermiculite with 3 %/5 % (w/w) addition of PVC (polyvinyl chloride)-MPs/PBAT (polybutylene adipate)-MPs. PVC-MPs and PBAT-MPs separately decreased nodule number by 33-100 % and 2.62-80.91 %. Transcriptome analysis showed that PVC-MPs affected more DEGs (differentially expressed genes) than PBAT-MPs, indicating PVC-MPs were more devastating for the symbiosis than PBAT-MPs. Functional annotation revealed that PVC-MPs and PBAT-MPs enriched DEGs related to biosynthesis pathways such as flavonoid, isoflavonoid, and phenylpropanoid, in peanut. And when the dose increased from 3 % to 5 %, PVC-MPs mainly enriched the pathways of starch and sucrose metabolism, alanine, aspartate and glutamate metabolism, diterpenoid biosynthesis, etc.; PBAT-MPs enriched cysteine and methionine metabolism, photosynthesis, MAPK signaling, and other pathways. These significantly enriched pathways functioned in reducing nodule number and promoting peanut tolerance to MPs stresses. This study reveals the effect of PVC-MPs and PBAT-MPs on peanut and rhizobium symbiosis, and provides new perspectives for legume production and environmental safety.
Asunto(s)
Arachis , Microplásticos , Cloruro de Polivinilo , Simbiosis , Arachis/microbiología , Arachis/metabolismo , Arachis/efectos de los fármacos , Microplásticos/toxicidad , Contaminantes del Suelo/toxicidad , Contaminantes del Suelo/metabolismo , Rhizobium/metabolismo , Rhizobium/efectos de los fármacos , Poliésteres/metabolismo , Redes y Vías Metabólicas/efectos de los fármacos , Bradyrhizobium/metabolismo , Bradyrhizobium/efectos de los fármacosRESUMEN
Soybean [Glycine max (L.) Merr.] has great economic and nutritional importance mainly due to its high protein content. All plant's N needs can be met by the symbiosis with elite Bradyrhizobium strains applied as inoculants to the seeds at sowing time; however, the increasing use of pesticides in seed treatments can impair the contribution of the biological nitrogen fixation. In this study, we report decreases in cell survival of two strains, B. japonicum SEMIA 5079 and B. elkanii SEMIA 587 in seeds inoculated and treated with StandakTop™, composed of the fungicides pyraclostrobin and thiophanate-methyl and the insecticide fipronil, the pesticides most used in soybean seed treatment in several countries. Cell death was enhanced with the time of exposure to the pesticides, and B. elkanii was less tolerant, with almost no detectable viable cells after 15 days. Change in colony morphology with smaller colonies was observed in the presence of the pesticides, being more drastic with the time of exposure, and attributed to an adaptive response towards survival in the presence of the abiotic stress. However, morphological changes were reversible after elimination of the stressing agent and symbiotic performance under controlled greenhouse conditions was similar between strains that had been or not exposed to the pesticides. In addition, no changes in DNA profiles (BOX-PCR) of both strains were observed after the contact with the pesticides. In two field experiments, impacting effects of the pesticides were observed mainly on the total N accumulated in grains of plants relying on both N2-fixation and N-fertilizer. Our data indicate that StandakTop® affects parameters never reported before, including colony morphology of Bradyrhizobium spp. and N metabolism and/or N remobilization to soybean grains.
Asunto(s)
Bradyrhizobium/crecimiento & desarrollo , Glycine max/microbiología , Plaguicidas/efectos adversos , Bradyrhizobium/efectos de los fármacos , Bradyrhizobium/metabolismo , Viabilidad Microbiana/efectos de los fármacos , Nitrógeno/metabolismo , Fijación del Nitrógeno/efectos de los fármacos , Glycine max/crecimiento & desarrollo , Glycine max/metabolismo , SimbiosisRESUMEN
A wide variety of leguminous plant-released (iso)flavonoids, such as genistein, are potential inducers of the nodulation (nod) genes of endosymbiotic rhizobia for the production of Nod factors, which are vital signaling molecules for triggering the symbiotic process. However, these (iso)flavonoids are generally thought to be toxic to the bacterial partner to varying degrees. Here, a novel TetR-like regulator gene of the soybean symbiont Bradyrhizobium diazoefficiens USDA110, bdtR (systematic designation blr7023), was characterized. It was found to be rapidly and preferentially induced by genistein, and its mutation resulted in significantly increased expression of the neighboring bll7019-bll7021 genes, encoding a multidrug resistance efflux pump system, in the absence of this isoflavonoid. Then, the transcriptional start site of BdtR was determined, and it was revealed that BdtR acted as a transcriptional repressor of the above efflux system through the binding of an AT-rich operator, which could be completely prevented by genistein. In addition, the ΔbdtR deletion mutant strain showed higher accumulation of extracellular genistein and became less susceptible to the isoflavonoid. In contrast, the inactivation of BdtR led to the significantly decreased induction of a nodulation gene (nodY) independent of the expression of nodD1 and nodW and to much weaker nodulation competitiveness. Taken together, the results show that BdtR plays an early sensing role in maintaining the intracellular homeostasis of genistein, helping to alleviate its toxic effect on this bacterium by negatively regulating neighboring genes encoding an efflux pump system while being essentially required for nodule occupancy competitiveness.[Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
Asunto(s)
Bradyrhizobium , Genisteína , Glycine max , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Bradyrhizobium/efectos de los fármacos , Bradyrhizobium/genética , Bradyrhizobium/metabolismo , Regulación Bacteriana de la Expresión Génica , Genisteína/farmacología , Glycine max/metabolismo , Glycine max/microbiología , SimbiosisRESUMEN
Arsenic (As) can be present naturally in groundwater from peanut fields, constituting a serious problem, as roots can accumulate and mobilize the metalloid to their edible parts. Understanding the redox changes in the legume exposed to As may help to detect potential risks to human health and recognize tolerance mechanisms. Thirty-days old peanut plants inoculated with Bradyrhizobium sp. strains (SEMIA6144 or C-145) were exposed to a realistic arsenate concentration, in order to unravel the redox response and characterize the oxidative stress indexes. Thus, root anatomy, reactive oxygen species detection by fluorescence microscopy and, ROS histochemical staining along with the NADPH oxidase activity were analyzed. Besides, photosynthetic pigments and damage to lipids and proteins were determined as oxidative stress indicators. Results showed that at 3 µM AsV, the cross-section areas of peanut roots were augmented; NADPH oxidase activity was significantly increased and O2˯and H2O2 accumulated in leaves and roots. Likewise, an increase in the lipid peroxidation and protein carbonyls was also observed throughout the plant regardless the inoculated strain, while chlorophylls and carotenes were increased only in those inoculated with Bradyrhizobium sp. C-145. Interestingly, the oxidative burst, mainly induced by the NADPH oxidase activity, and the consequent oxidative stress was strain-dependent and organ-differential. Additionally, As modifies the root anatomy, acting as a possibly first defense mechanism against the metalloid entry. All these findings allowed us to conclude that the redox response of peanut is conditioned by the rhizobial strain, which contributes to the importance of effectively formulating bioinoculants for this crop.
Asunto(s)
Arachis/microbiología , Arsénico/toxicidad , Bradyrhizobium/fisiología , Estrés Oxidativo/fisiología , Arachis/efectos de los fármacos , Arachis/metabolismo , Arachis/fisiología , Arseniatos , Arsénico/metabolismo , Bradyrhizobium/efectos de los fármacos , Bradyrhizobium/metabolismo , Clorofila/metabolismo , Peróxido de Hidrógeno/metabolismo , Peroxidación de Lípido , Oxidación-Reducción , Raíces de Plantas/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Simbiosis/efectos de los fármacosRESUMEN
The pathogenicity and antimicrobial properties of engineered nanomaterials (ENMs) are relatively well studied. However, less is known regarding the interactions of ENMs and agriculturally beneficial microorganisms that affect food security. Nanoceria (CeO2 nanoparticles (NPs)), multiwall carbon nanotubes (MWCNTs), graphene nanoplatelets (GNPs), and carbon black (CB) have been previously shown to inhibit symbiotic N2 fixation in soybeans, but direct rhizobial susceptibility is uncertain. Here, Bradyrhizobium diazoefficiens associated with symbiotic N2 fixation in soybeans is assessed, evaluating the role of soybean root exudates (RE) on ENM-bacterial interactions and the effects of CeO2 NPs, MWCNTs, GNPs, and CB on bacterial growth and gene expression. Although bacterial growth is inhibited by 50 mg L-1 CeO2 NPs, MWCNTs, and CB, all ENMs at 0.1 and 10 mg L-1 cause a global transcriptomic response that is mitigated by RE. ENMs may interfere with plant-bacterial signaling, as evidenced by suppressed upregulation of genes induced by RE, and downregulation of genes encoding transport RNA, which facilitates nodulation signaling. MWCNTs and CeO2 NPs inhibit the expression of genes conferring B. diazoefficiens nodulation competitiveness. Surprisingly, the transcriptomic effects on B. diazoefficiens are similar for these two ENMs, indicating that physical, not chemical, ENM properties explain the observed effects.
Asunto(s)
Bradyrhizobium , Cerio , Glycine max , Nanotubos de Carbono , Nodulación de la Raíz de la Planta , Bradyrhizobium/efectos de los fármacos , Cerio/química , Cerio/farmacología , Nanotubos de Carbono/química , Nodulación de la Raíz de la Planta/efectos de los fármacos , Glycine max/microbiologíaRESUMEN
High Content Analysis (HCA) has become a cornerstone of cellular analysis within the drug discovery industry. To expand the capabilities of HCA, we have applied the same analysis methods, validated in numerous mammalian cell models, to microbiology methodology. Image acquisition and analysis of various microbial samples, ranging from pure cultures to culture mixtures containing up to three different bacterial species, were quantified and identified using various machine learning processes. These HCA techniques allow for faster cell enumeration than standard agar-plating methods, identification of "viable but not plate culturable" microbe phenotype, classification of antibiotic treatment effects, and identification of individual microbial strains in mixed cultures. These methods greatly expand the utility of HCA methods and automate tedious and low-throughput standard microbiological methods.
Asunto(s)
Bacterias/metabolismo , Aprendizaje Automático , Antibacterianos/farmacología , Bacillus megaterium/efectos de los fármacos , Bacillus megaterium/ultraestructura , Bacterias/química , Bacterias/efectos de los fármacos , Proteínas Bacterianas/análisis , Bradyrhizobium/efectos de los fármacos , Bradyrhizobium/crecimiento & desarrollo , Bradyrhizobium/metabolismo , Bradyrhizobium/ultraestructura , Recuento de Colonia Microbiana , Escherichia coli/efectos de los fármacos , Escherichia coli/ultraestructura , Pseudomonas fluorescens/efectos de los fármacos , Pseudomonas fluorescens/ultraestructuraRESUMEN
As inducers of nodulation (nod) genes, flavonoids play an important role in the symbiotic interaction between rhizobia and legumes. However, in addition to the control of expression of nod genes, many other effects of flavonoids on rhizobial cells have been described. Here, we show that the flavonoid naringenin stimulates the growth of the photosynthetic Bradyrhizobium sp. strain ORS285. This growth-stimulating effect was still observed for strain ORS285 with nodD1, nodD2, or the naringenin-degrading fde operon deleted. Phenotypic microarray analysis indicates that in cells grown in the presence of naringenin, the glycerol and fatty acid metabolism is activated. Moreover, electron microscopic and enzymatic analyses show that polyhydroxy alkanoate metabolism is altered in cells grown in the presence of naringenin. Although strain ORS285 was able to degrade naringenin, a fraction was converted into an intensely yellow-colored molecule with an m/z (+) of 363.0716. Further analysis indicates that this molecule is a hydroxylated and O-methylated form of naringenin. In contrast to naringenin, this derivative did not induce nod gene expression, but it did stimulate the growth of strain ORS285. We hypothesize that the growth stimulation and metabolic changes induced by naringenin are part of a mechanism to facilitate the colonization and infection of naringenin-exuding host plants.
Asunto(s)
Bradyrhizobium , Fabaceae , Flavanonas , Rhizobium , Proteínas Bacterianas/metabolismo , Bradyrhizobium/efectos de los fármacos , Bradyrhizobium/crecimiento & desarrollo , Bradyrhizobium/metabolismo , Flavanonas/genética , Flavanonas/metabolismo , Flavanonas/farmacología , Flavonoides , Genes Bacterianos/genética , Simbiosis/genéticaRESUMEN
Photobacteria phosoreum or Escherichia coli are widely used in the scientific, industrial, and regulatory industries for evaluating the toxicity of pollutants against the soil microbial community. The organisms, however, are not part of the soil microbiota and the toxicity data obtained using these organisms could be misleading. Analysis of microbiota present in the soil obtained from across the world indicates that organisms from the Bradyrhizobium genus are the most ubiquitous of all microorganisms. Playing a critical role in nitrogen fixation and soil fertility, organisms from this genus should be used for studying the toxicity of pollutants. Indeed, we propose that Bradyrhizobium japonicum USDA110 be used as a model organism for screening pollutants for toxicity against a soil microbial community.
Asunto(s)
Bradyrhizobium/efectos de los fármacos , Microbiología del Suelo , Contaminantes del Suelo/toxicidad , Proteínas Bacterianas , Microbiota , Fijación del Nitrógeno , Especies Centinela , SueloRESUMEN
Nodulation competition is a key factor that limits symbiotic nitrogen fixation between rhizobia and their host legumes. Soybean root exudates (SREs) are thought to act as signals that influence Bradyrhizobium ability to colonize roots and to survive in the rhizosphere, and thus they act as a key determinant of nodulation competitiveness. In order to find the competitiveness-related genes in B. diazoefficiens, the transcriptome of two SREs treated B. diazoefficiens with completely different nodulation abilities (B. diazoefficiens 4534 and B. diazoefficiens 4222) were sequenced and compared. In SREs treated strain 4534 (SREs-4534), 253 unigenes were up-regulated and 204 unigenes were down-regulated. In SREs treated strain 4534 (SREs-4222), the numbers of up- and down-regulated unigenes were 108 and 185, respectively. There were considerable differences between the SREs-4534 and SREs-4222 gene expression profiles. Some differentially expressed genes are associated with a two-component system (i.g., nodW, phyR-σEcfG), bacterial chemotaxis (i.g., cheA, unigene04832), ABC transport proteins (i.g., unigene02212), IAA (indole-3-acetic acid) metabolism (i.g., nthA, nthB), and metabolic fitness (i.g., put.), which may explain the higher nodulation competitiveness of B. diazoefficiens in the rhizosphere. Our results provide a comprehensive transcriptomic resource for SREs treated B. diazoefficiens and will facilitate further studies on competitiveness-related genes in B. diazoefficiens.
Asunto(s)
Bradyrhizobium/genética , Genes Bacterianos , Nodulación de la Raíz de la Planta , Bradyrhizobium/efectos de los fármacos , Bradyrhizobium/metabolismo , Bradyrhizobium/patogenicidad , Extractos Vegetales/farmacología , Rizosfera , Glycine max/química , Glycine max/microbiología , TranscriptomaRESUMEN
Random mutagenesis in a symbiotic nitrogen-fixing Bradyrhizobium liaoningense CCNWSX0360 (Bln0360) using Tn5 identified five copper (Cu) resistance-related genes. They were functionally sorted into three groups: transmembrane transport (cueA and tolC); oxidation (copA); and protection of the membrane barrier (lptE and ctpA). The gene cueA, together with the upstream csoR (Cu-sensitive operon repressor), constituted a csoR-cueA divergon which plays a crucial role in Cu homeostasis. Deletion of cueA decreased the Cu tolerance of cells, and complementation of this mutant restored comparable Cu resistance to that of the wild-type. Transcriptional and fusion expression analysis demonstrated that csoR-cueA divergon was up-regulated by both the monovalent Cu+ and divalent Zn2+/Cd2+, and negatively regulated by transcriptional repressor CsoR, via a bidirectional promoter. Deletion of csoR renders the cell hyper-resistant to Cu, Zn and Cd. Although predicted to encode a Cu transporting P-type ATPase (CueA), cueA also conferred resistance to zinc and cadmium; two putative N-MBDs (N-terminal metal binding domains) of CueA were required for the Cu/Zn/Cd tolerance. Moreover, cueA is needed for nodulation competitiveness of B. liaoningense in Cu rich conditions. Together, the results demonstrated a crucial role for the csoR-cueA divergon as a component of the multiple-metal resistance machinery in B. liaoningense.
Asunto(s)
Proteínas Bacterianas/metabolismo , Bradyrhizobium/efectos de los fármacos , Cadmio/metabolismo , Cobre/metabolismo , Farmacorresistencia Bacteriana , Zinc/metabolismo , Proteínas Bacterianas/genética , Bradyrhizobium/genética , Elementos Transponibles de ADN , Eliminación de Gen , Perfilación de la Expresión Génica , Prueba de Complementación Genética , Proteínas de Transporte de Membrana/genética , Proteínas de Transporte de Membrana/metabolismo , Mutagénesis Insercional , Proteínas Represoras/genética , Proteínas Represoras/metabolismoRESUMEN
Small open reading frames (sORFs) and genes for non-coding RNAs are poorly investigated components of most genomes. Our analysis of 1391 ORFs recently annotated in the soybean symbiont Bradyrhizobium japonicum USDA 110 revealed that 78% of them contain less than 80 codons. Twenty-one of these sORFs are conserved in or outside Alphaproteobacteria and most of them are similar to genes found in transposable elements, in line with their broad distribution. Stabilizing selection was demonstrated for sORFs with proteomic evidence and bll1319_ISGA which is conserved at the nucleotide level in 16 alphaproteobacterial species, 79 species from other taxa and 49 other Proteobacteria. Further we used Northern blot hybridization to validate ten small RNAs (BjsR1 to BjsR10) belonging to new RNA families. We found that BjsR1 and BjsR3 have homologs outside the genus Bradyrhizobium, and BjsR5, BjsR6, BjsR7, and BjsR10 have up to four imperfect copies in Bradyrhizobium genomes. BjsR8, BjsR9, and BjsR10 are present exclusively in nodules, while the other sRNAs are also expressed in liquid cultures. We also found that the level of BjsR4 decreases after exposure to tellurite and iron, and this down-regulation contributes to survival under high iron conditions. Analysis of additional small RNAs overlapping with 3'-UTRs revealed two new repetitive elements named Br-REP1 and Br-REP2. These REP elements may play roles in the genomic plasticity and gene regulation and could be useful for strain identification by PCR-fingerprinting. Furthermore, we studied two potential toxin genes in the symbiotic island and confirmed toxicity of the yhaV homolog bll1687 but not of the newly annotated higB homolog blr0229_ISGA in E. coli. Finally, we revealed transcription interference resulting in an antisense RNA complementary to blr1853, a gene induced in symbiosis. The presented results expand our knowledge on sORFs, non-coding RNAs and repetitive elements in B. japonicum and related bacteria.
Asunto(s)
Bradyrhizobium/genética , Sistemas de Lectura Abierta/genética , ARN Bacteriano/genética , ARN no Traducido/genética , Secuencias Repetitivas de Ácidos Nucleicos/genética , Regiones no Traducidas 3'/genética , Secuencia de Bases , Bradyrhizobium/efectos de los fármacos , Bradyrhizobium/fisiología , Secuencia Conservada , Regulación hacia Abajo/efectos de los fármacos , Hierro/farmacología , Estrés Fisiológico/efectos de los fármacos , Estrés Fisiológico/genética , Toxinas Biológicas/genéticaRESUMEN
Cyclic (1â3, 1â6)-ß-glucans are water soluble, biocompatible polymers with potential applications in food and pharmaceutical industries but have not yet been exploited due to their poor yield. In the present study statistical experimental design methodology was employed to improve their production. Initial screening indicated arabinose and peptone as best carbon and nitrogen source respectively, for glucan production. Arabinose and osmolyte concentrations as well as pH significantly contributed to the glucan production. Central composite design indicated a significant interaction between osmolyte concentration and pH on glucan production. The maximum amount of cyclic glucan produced was 6.7g/L in a 2.5L reactor in batch conditions. The logistic equation for cell growth and Luedeking-Piret equation for glucan production could satisfactorily simulate the batch kinetics data. Cyclic ß-glucans could efficiently encapsulate a hydrophobic molecule, curcumin and increase its solubility in water, thus indicating that these glucans have potential as drug delivery systems.
Asunto(s)
Bradyrhizobium/metabolismo , Glucanos/biosíntesis , Modelos Teóricos , Técnicas de Cultivo Celular por Lotes , Biomasa , Reactores Biológicos/microbiología , Bradyrhizobium/efectos de los fármacos , Bradyrhizobium/crecimiento & desarrollo , Carbono/farmacología , Curcumina/farmacología , Cinética , Nitrógeno/farmacología , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , Espectroscopía Infrarroja por Transformada de Fourier , Factores de TiempoRESUMEN
The Relevance. At the recent years in soybean crops the quantity of plant pathogenic fungi has increased. The fungicides of systemic and contact action have been applicated intensively against of them. After introducing into the soil fungicides and/or their deg- radation products can to disrupt the activities of non-target objects - beneficial soil mi- croorganisms, inhibit nodulation process and the nitrogen-fixing activity of diazotrophs. The purpose of the work was to investigate the impact of combined application of fungi- cides with inoculation on the soybean symbiotic system and rhizosphere microorganisms. The Methods. The microbiological and statistical methods, gas chromatography method. The Results. Inoculation of seeds by the highly active Bradyrhizobiumjaponicum UCM B-6035, UCM B-6018 and UCM B-6023 strains the activity of nitrogen-fixing symbiotic systems increased by 1.4-3.4 times in comparison with the variant without of fungicides application and bacterization. Seed treatment by Vitavaks 200 FF fungicide caused a de- crease of'nitrogen-fixing activity of rhizobia industrial strains in symbiosis with soybean by 3-5 times. The seeds inoculation by B. japonicum UCM B-6035 strain promoted to reduce the negative impact of the Maxim Star 025 FS fungicide on the nitrogenase activity of nodulation apparatus. The positive effect of seeds bacterization was observed in the in- crease of the quantity of rhizosphere microorganisms of main ecological trophic groups. In the variant with seed treatment by Maxim Star 025 FS and Kinto duo fungicides was found a decrease in the number of microorganisms of studied groups in comparison with the control variant; the Vitavaks 200 FF fungicide application promoted to improve of these microorganisms development compared with the variant without the fungicides application and bacterization. At the inoculation of rhizobia industrial strains the negative effect of the Maxim Star 025 FS and Kinto duo fungicides to oligoazotrophic and prototrophic micro- organisms was not observed. The Conclusion. The symbiotic system of variant with the combined application of the Kinto duo fungicide with B. japonicum UCM B-6023 strain characterized by the highest nodulation and nitrogen-fixing activity.
Asunto(s)
Bradyrhizobium/efectos de los fármacos , Carboxina/farmacología , Fungicidas Industriales/farmacología , Glycine max/efectos de los fármacos , Nodulación de la Raíz de la Planta/efectos de los fármacos , Bradyrhizobium/crecimiento & desarrollo , Bradyrhizobium/metabolismo , Fijación del Nitrógeno/efectos de los fármacos , Nodulación de la Raíz de la Planta/fisiología , Rizosfera , Semillas/efectos de los fármacos , Semillas/crecimiento & desarrollo , Semillas/microbiología , Glycine max/crecimiento & desarrollo , Glycine max/microbiología , Simbiosis/fisiologíaRESUMEN
The features of the soybean symbiotic systems formation and carry out the complex es- timate of the rhizobium nodulation ability at the seed inoculation of the microbial composi- tions on the bases of nodule bacteria, azotobacter and phytolectins (soybean seeds lectin, wheat germ agglutinin) were studied in the green-house experiments with a soil cultures. It was shown, that complex inoculants accelerate the process of becoming infected of plants by rhizobia in the early stages of soybean development; contribute to the expansion of the spectrum of genetically determined ability of nodule bacteria in the formation of a certain number of nodules on the host plant during the growing season as well as the formation of more root nodules with more of their weight during the second half of the growing season of soybean and significant increase mass of the one nodule and also slow the root nodules aging process at the end of the growing season compared with a rhizobial monoinoculant. It was proposed to use a complex of criteria in the estimating of the rhizobia nodulation ability in the microbial compositions: "nodulation activity", "nodulation range", "the num- ber of nodules on the plant", "mass of nodules per plant", "mass of one nodule", which are indicative for different stages of the symbiosis formation.
Asunto(s)
Azotobacter/crecimiento & desarrollo , Bradyrhizobium/crecimiento & desarrollo , Glycine max/microbiología , Nodulación de la Raíz de la Planta/fisiología , Semillas/microbiología , Simbiosis/fisiología , Azotobacter/efectos de los fármacos , Azotobacter/metabolismo , Bradyrhizobium/efectos de los fármacos , Bradyrhizobium/metabolismo , Medios de Cultivo/química , Medios de Cultivo/farmacología , Lectinas de Plantas/farmacología , Nodulación de la Raíz de la Planta/efectos de los fármacos , Rizosfera , Semillas/efectos de los fármacos , Semillas/crecimiento & desarrollo , Proteínas de Soja/farmacología , Glycine max/efectos de los fármacos , Glycine max/crecimiento & desarrollo , Simbiosis/efectos de los fármacos , Aglutininas del Germen de Trigo/farmacologíaRESUMEN
We cloned and sequenced the waaL (rfaL) gene from Bradyrhizobium japonicum, which infects soybean and forms nitrogen-fixing nodules on soybean roots. waaL has been extensively studied in the lipopolysaccharide (LPS) biosynthesis of enteric bacteria, but little is known about its function in (brady)rhizobial LPS architecture. To characterize its role as O-antigen ligase in the LPS biosynthesis pathway, we constructed a waaL knock-out mutant and its complemented strain named JS015 and CS015, respectively. LPS analysis showed that an LPS structure of JS015 is deficient in O-antigen as compared to that of the wild type and complemented strain CS015, suggesting that WaaL ligates the O-antigen to lipid A-core oligosaccharide to form a complete LPS. JS015 also revealed increased cell surface hydrophobicity, but it showed decreased motility in soft agar plates. In addition to the alteration in cell surface properties, disruption of the waaL gene caused increased sensitivity of JS015 to hydrogen peroxide, osmotic pressure, and novobiocin. Specifically, plant tests revealed that JS015 failed to nodulate the host plant soybean, indicating that the rhizobial waaL gene is responsible for the establishment of a symbiotic relationship between soybean and B. japonicum.
Asunto(s)
Adaptación Fisiológica , Proteínas Bacterianas/genética , Bradyrhizobium/genética , Genes Bacterianos , Glycine max/microbiología , Interacciones Hidrofóbicas e Hidrofílicas , Estrés Fisiológico , Simbiosis , Adaptación Fisiológica/efectos de los fármacos , Proteínas Bacterianas/metabolismo , Bradyrhizobium/efectos de los fármacos , Bradyrhizobium/fisiología , Membrana Celular/metabolismo , Electroforesis en Gel de Poliacrilamida , Flagelos/metabolismo , Flagelos/ultraestructura , Lipopolisacáridos/metabolismo , Datos de Secuencia Molecular , Movimiento , Mutación , Novobiocina/toxicidad , Antígenos O , Presión Osmótica/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacos , Nodulación de la Raíz de la Planta/efectos de los fármacos , Nodulación de la Raíz de la Planta/genética , Nódulos de las Raíces de las Plantas/efectos de los fármacos , Nódulos de las Raíces de las Plantas/microbiología , Glycine max/efectos de los fármacos , Estrés Fisiológico/efectos de los fármacos , Estrés Fisiológico/genética , Simbiosis/efectos de los fármacosRESUMEN
Bacterial ability to colonize the rhizosphere of plants in arsenic (As) contaminated soils is highly important for symbiotic and free-living plant growth-promoting rhizobacteria (PGPR) used as inoculants, since they can contribute to enhance plant As tolerance and limit metalloid uptake by plants. The aim of this work was to study the effect of As on growth, exopolysaccharide (EPS) production, biofilm formation and motility of two strains used as soybean inoculants, Bradyrhizobium japonicum E109 and Azospirillum brasilense Az39. The metabolism of arsenate (As(V)) and arsenite (As(III)) and their removal and/or possible accumulation were also evaluated. The behavior of both bacteria under As treatment was compared and discussed in relation to their potential for colonizing plant rhizosphere with high content of the metalloid. B. japonicum E109 growth was reduced with As(III) concentration from 10 µM while A. brasilense Az39 showed a reduction of growth with As(III) from 500 µM. EPS and biofilm production increased significantly under 25 µM As(III) for both strains. Moreover, this was more notorious for Azospirillum under 500 µM As(III), where motility was seriously affected. Both bacterial strains showed a similar ability to reduce As(V). However, Azospirillum was able to oxidize more As(III) (around 53%) than Bradyrhizobium (17%). In addition, both strains accumulated As in cell biomass. The behavior of Azospirillum under As treatments suggests that this strain would be able to colonize efficiently As contaminated soils. In this way, inoculation with A. brasilense Az39 would positively contribute to promoting growth of different plant species under As treatment.
Asunto(s)
Arsénico/toxicidad , Azospirillum brasilense/efectos de los fármacos , Bradyrhizobium/efectos de los fármacos , Contaminantes del Suelo/toxicidad , Arsénico/química , Azospirillum brasilense/metabolismo , Biopelículas , Biomasa , Bradyrhizobium/metabolismo , Viabilidad Microbiana/efectos de los fármacos , Movimiento , Contaminantes del Suelo/químicaRESUMEN
Soil bacteria can exhibit extensive antibiotic resistomes and act as reservoirs of important antibiotic resistance traits. However, the geographic sources and evolutionary drivers of resistance traits are poorly understood in these natural settings. We investigated the prevalence, spatial structure and evolutionary drivers of multidrug resistance in natural populations of Bradyrhizobium, a cosmopolitan bacterial lineage that thrives in soil and aquatic systems as well as in plant and human hosts. We genotyped > 400 isolates from plant roots and soils across California and assayed 98 of them for resistance traits against 17 clinically relevant antibiotics. We investigated the geographic and phylogenetic structure of resistance traits, and analysed correlations of resistance with strain abundance, host infection capacity and in vitro fitness. We found: (i) multidrug resistance at all sites, (ii) subsets of resistance traits that are spatially structured and (iii) significant associations between resistance traits and increased strain abundance or host infection capacity. Our results highlight multiple selective factors that can result in the spread of resistance traits in native Bradyrhizobium populations.
Asunto(s)
Bradyrhizobium/efectos de los fármacos , Bradyrhizobium/aislamiento & purificación , Farmacorresistencia Bacteriana Múltiple , Raíces de Plantas/microbiología , Selección Genética , Microbiología del Suelo , California , GenotipoRESUMEN
BACKGROUND: Strain CPAC 7 (=SEMIA 5080) was recently reclassified into the new species Bradyrhizobium diazoefficiens; due to its outstanding efficiency in fixing nitrogen, it has been used in commercial inoculants for application to crops of soybean [Glycine max (L.) Merr.] in Brazil and other South American countries. Although the efficiency of B. diazoefficiens inoculant strains is well recognized, few data on their protein expression are available. RESULTS: We provided a two-dimensional proteomic reference map of CPAC 7 obtained under free-living conditions, with the successful identification of 115 spots, representing 95 different proteins. The results highlighted the expression of molecular determinants potentially related to symbiosis establishment (e.g. inositol monophosphatase, IMPase), fixation of atmospheric nitrogen (N2) (e.g. NifH) and defenses against stresses (e.g. chaperones). By using bioinformatic tools, it was possible to attribute probable functions to ten hypothetical proteins. For another ten proteins classified as "NO related COG" group, we analyzed by RT-qPCR the relative expression of their coding-genes in response to the nodulation-gene inducer genistein. Six of these genes were up-regulated, including blr0227, which may be related to polyhydroxybutyrate (PHB) biosynthesis and competitiveness for nodulation. CONCLUSIONS: The proteomic map contributed to the identification of several proteins of B. diazoefficiens under free-living conditions and our approach-combining bioinformatics and gene-expression assays-resulted in new information about unknown genes that might play important roles in the establishment of the symbiosis with soybean.
Asunto(s)
Bradyrhizobium/metabolismo , Proteómica/métodos , Simbiosis , Proteínas Bacterianas/metabolismo , Bradyrhizobium/efectos de los fármacos , Bradyrhizobium/genética , Bradyrhizobium/crecimiento & desarrollo , Biología Computacional , Electroforesis en Gel Bidimensional , Regulación Bacteriana de la Expresión Génica/efectos de los fármacos , Genisteína/farmacología , Genoma Bacteriano , Fijación del Nitrógeno , Sistemas de Lectura Abierta/genética , Estrés FisiológicoRESUMEN
A Bradyrhizobium japonicum mutant defective in the gene encoding the high-affinity Mn(2+) transporter MntH has a severe growth phenotype under manganese limitation. Here, we isolated suppressor mutants of an mntH strain that grew under manganese limitation, and activities of high-affinity Mn(2+) transport and Mn(2+) -dependent enzymes were partially rescued. The suppressor strains harbour gain-of-function mutations in the gene encoding the Mg(2+) channel MgtE. The MgtE variants likely allow Mn(2+) entry via loss of a gating mechanism that normally holds the transporter in the closed state when cellular Mg(2+) levels are high. Both MgtE-dependent and MgtE-independent suppressor phenotypes were recapitulated by magnesium-limited growth of the mntH strain. Growth studies of wild-type cells suggest that manganese is toxic to cells when environmental magnesium is low. Moreover, extracellular manganese and magnesium levels were manipulated to inhibit growth without substantially altering the intracellular content of either metal, implying that manganese toxicity depends on its cellular distribution rather than the absolute concentration. Mg(2+) -dependent enzyme activities were found to be inhibited or stimulated by Mn(2+) . We conclude that Mn(2+) can occupy Mg(2+) binding sites in cells, and suggest that Mg(2+) -dependent processes are targets of manganese toxicity.