RESUMO
Metallothioneins (MTs) constitute a heterogeneous family of ubiquitous metal ion-binding proteins. In plants, MTs participate in the regulation of cell growth and proliferation, protection against heavy metal stress, oxidative stress responses, and responses to pathogen attack. Despite their wide variety of functions, the role of MTs in symbiotic associations, specifically nodule-fabacean symbiosis, is poorly understood. Here, we analyzed the role of the PvMT1A gene in Phaseolus vulgaris-Rhizobium tropici symbiosis using bioinformatics and reverse genetics approaches. Using in silico analysis, we identified six genes encoding MTs in P. vulgaris, which were clustered into three of the four classes described in plants. PvMT1A transcript levels were significantly higher in roots inoculated with R. tropici at 7 and 30 days post inoculation (dpi) than in non-inoculated roots. Functional analysis showed that downregulating PvMT1A by RNA interference (RNAi) reduced the number of infection events at 7 and 10 dpi and the number of nodules at 14 and 21 dpi. In addition, nodule development was negatively affected in PvMT1A:RNAi transgenic roots, and these nodules displayed a reduced nitrogen fixation rate at 21 dpi. These results strongly suggest that PvMT1A plays an important role in the infection process and nodule development in P. vulgaris during rhizobial symbiosis.
Assuntos
Metalotioneína/metabolismo , Phaseolus , Proteínas de Plantas/metabolismo , Rhizobium/crescimento & desenvolvimento , Nódulos Radiculares de Plantas , Simbiose , Phaseolus/metabolismo , Phaseolus/microbiologia , Nódulos Radiculares de Plantas/metabolismo , Nódulos Radiculares de Plantas/microbiologiaRESUMO
Enzymes can be very useful on exopolysaccharides (EPS) research, can be used at elucidation and also to modify the polysaccharides' structure in order to alter their physical properties. Thus, the reduction of the molecular mass could increase applications of these biopolymers. Therefore, the EPS production of different rhizobia and the action of xanthan lyase on its structures were evaluated. The strains produced significant amounts of EPS, and it was noticed that are heteropolysaccharides, composed galactose and glucose. Both EPS and xanthan were modified on ß-glycosidic bonds, the mannose was removed of xanthan had but the EPS was affected in the CO stretching vibration, where the glucuronic acid removed from of your structure. The ester/carboxylic acid portions affected functional groups of the acetate/succinate, methyl carbons of the O-acetyl and pyruvate methyl groups in addition to affect the carbons the main pyranoid. The Resistance to temperature increase of the EPS was observed, made possible by the activity of the lyase. EPS has the ability to form stable gels at higher temperatures and anionic feature can be used on solubilization and controlled release of substances. Modified EPS knowledge will presently facilitate future investigations relating the structure of the rhizobia polysaccharide against rheological properties.
Assuntos
Carbono-Oxigênio Liases/metabolismo , Polissacarídeos Bacterianos/biossíntese , Polissacarídeos Bacterianos/química , Rhizobium/metabolismo , Concentração de Íons de Hidrogênio , Monossacarídeos/análise , Polissacarídeos Bacterianos/metabolismo , Rhizobium/crescimento & desenvolvimentoRESUMO
Nitrogen-limited conditions are considered to be a prerequisite for legume-rhizobial symbiosis, but the effects of nitrate-rich conditions on symbiotic status remain poorly understood. We addressed this issue by examining rhizobial (Rhizobim tropici) and arbusclar mycorrhizal (Glomus intraradices) symbiosis in Phaseolus vulgaris L. cv. Negro Jamapa under nitrate pre-incubation and continuous nitrate conditions. Our results indicate that nitrate pre-incubation, independent of the concentration, did not affect nodule development. However, the continuous supply of nitrate at high concentrations impaired nodule maturation and nodule numbers. Low nitrate conditions, in addition to positively regulating nodule number, biomass, and nitrogenase activity, also extended the span of nitrogen-fixing activity. By contrast, for arbuscular mycorrhizae, continuous 10 and 50 mmol/L nitrate increased the percent root length colonization, concomitantly reduced arbuscule size, and enhanced ammonia transport without affecting phosphate transport. Therefore, in this manuscript, we have proposed the importance of nitrate as a positive regulator in promoting both rhizobial and mycorrhizal symbiosis in the common bean.
Assuntos
Micorrizas/fisiologia , Nitratos/farmacologia , Phaseolus/microbiologia , Phaseolus/fisiologia , Rhizobium/fisiologia , Simbiose/efeitos dos fármacos , Compostos de Amônio/metabolismo , Biomassa , Tamanho Celular/efeitos dos fármacos , Contagem de Colônia Microbiana , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Proteínas de Membrana Transportadoras/genética , Proteínas de Membrana Transportadoras/metabolismo , Micorrizas/efeitos dos fármacos , Fixação de Nitrogênio/efeitos dos fármacos , Fixação de Nitrogênio/genética , Nitrogenase/metabolismo , Phaseolus/efeitos dos fármacos , Phaseolus/genética , Fenótipo , Fósforo/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Brotos de Planta/efeitos dos fármacos , Brotos de Planta/crescimento & desenvolvimento , Rhizobium/efeitos dos fármacos , Rhizobium/crescimento & desenvolvimento , Nódulos Radiculares de Plantas/efeitos dos fármacos , Nódulos Radiculares de Plantas/fisiologia , Simbiose/genéticaRESUMO
Halo-tolerant, auxin producing bacteria could be used to induce salt tolerance in plants. A number of Rhizobium and auxin producing rhizobacterial strains were assessed for their ability to tolerate salt stress by conducting osmoadaptation assay. The selected strains were further screened for their ability to induce osmotic stress tolerance in mung bean seedlings under salt-stressed axenic conditions in growth pouch/jar trials. Three most effective strains of Rhizobium and Pseudomonas containing ACC-deaminase were evaluated in combination, for their ability to induce osmotic stress tolerance in mung bean at original, 4, and 6 dS m-1 under axenic conditions. Results showed that sole inoculation of Rhizobium and Pseudomonas strains improved the total dry matter up to 1.4, and 1.9 fold, respectively, while the increase in salt tolerance index was improved up to 1.3 and 2.0 fold by the Rhizobium and Pseudomonas strains, respectively. However, up to 2.2 fold increase in total dry matter and salt tolerance index was observed due to combined inoculation of Rhizobium and Pseudomonas strains. So, combined application of Rhizobium and Pseudomonas strains could be explored as an effective strategy to induce osmotic stress tolerance in mung bean.
Assuntos
Fabaceae/microbiologia , Fabaceae/fisiologia , Ácidos Indolacéticos/metabolismo , Pressão Osmótica , Pseudomonas/crescimento & desenvolvimento , Rhizobium/crescimento & desenvolvimento , Estresse Fisiológico , Microbiologia do SoloRESUMO
Halo-tolerant, auxin producing bacteria could be used to induce salt tolerance in plants. A number of Rhizobium and auxin producing rhizobacterial strains were assessed for their ability to tolerate salt stress by conducting osmoadaptation assay. The selected strains were further screened for their ability to induce osmotic stress tolerance in mung bean seedlings under salt-stressed axenic conditions in growth pouch/jar trials. Three most effective strains of Rhizobium and Pseudomonas containing ACC-deaminase were evaluated in combination, for their ability to induce osmotic stress tolerance in mung bean at original, 4, and 6 dS m(-1) under axenic conditions. Results showed that sole inoculation of Rhizobium and Pseudomonas strains improved the total dry matter up to 1.4, and 1.9 fold, respectively, while the increase in salt tolerance index was improved up to 1.3 and 2.0 fold by the Rhizobium and Pseudomonas strains, respectively. However, up to 2.2 fold increase in total dry matter and salt tolerance index was observed due to combined inoculation of Rhizobium and Pseudomonas strains. So, combined application of Rhizobium and Pseudomonas strains could be explored as an effective strategy to induce osmotic stress tolerance in mung bean.
Assuntos
Fabaceae/microbiologia , Fabaceae/fisiologia , Ácidos Indolacéticos/metabolismo , Pressão Osmótica , Pseudomonas/crescimento & desenvolvimento , Rhizobium/crescimento & desenvolvimento , Estresse Fisiológico , Microbiologia do SoloRESUMO
The aim of this work was to characterize rhizobia isolated from the root nodules of cowpea (Vigna unguiculata) plants cultivated in Amazon soils samples by means of ARDRA (Amplified rDNA Restriction Analysis) and sequencing analysis, to know their phylogenetic relationships. The 16S rRNA gene of rhizobia was amplified by PCR (polymerase chain reaction) using universal primers Y1 and Y3. The amplification products were analyzed by the restriction enzymes HinfI, MspI and DdeI and also sequenced with Y1, Y3 and six intermediate primers. The clustering analysis based on ARDRA profiles separated the Amazon isolates in three subgroups, which formed a group apart from the reference isolates of Bradyrhizobium japonicum and Bradyrhizobium elkanii. The clustering analysis of 16S rRNA gene sequences showed that the fast-growing isolates had similarity with Enterobacter, Rhizobium, Klebsiella and Bradyrhizobium and all the slow-growing clustered close to Bradyrhizobium.
Assuntos
Sequência de Bases , Bradyrhizobium/crescimento & desenvolvimento , Bradyrhizobium/isolamento & purificação , Fabaceae/crescimento & desenvolvimento , Amplificação de Genes , Técnicas In Vitro , Reação em Cadeia da Polimerase/métodos , Rhizobium/crescimento & desenvolvimento , Rhizobium/isolamento & purificação , MétodosRESUMO
The impact of different defoliation intensities on the ability of Lotus tenuis plants to regrowth, mobilise nutrients and to associate with native AM fungi and Rhizobium in a saline-sodic soil was investigated. After 70 days, plants were subjected to 0, 25, 50, 75 and 100% defoliation and shoot regrowth was assessed at the end of subsequent 35 days. Compared to non-defoliated plants, low or moderate defoliation up to 75% did not affect shoot regrowth. However, 100% treatment affected shoot regrowth and the clipped plants were not able to compensate the growth attained by non-defoliated plants. Root growth was more affected by defoliation than shoot growth. P and N concentrations in shoots and roots increased with increasing defoliation while Na(+) concentration in shoots of non-defoliated and moderately defoliated plants was similar. Non-defoliated and moderately defoliated plants prevented increases of Na(+) concentration in shoots through both reducing Na(+) uptake and Na(+) transport to shoots by accumulating Na(+) in roots. At high defoliation, the salinity tolerance mechanism is altered and Na(+) concentration in shoots was higher than in roots. Reduction in the photosynthetic capacity induced by defoliation neither changed the root length colonised by AM fungi nor arbuscular colonisation but decreased the vesicular colonisation. Spore density did not change, but hyphal density and Rhizobium nodules increased with defoliation. The strategy of the AM symbiont consists in investing most of the C resources to preferentially retain arbuscular colonisation as well as inoculum density in the soil.
Assuntos
Lotus/microbiologia , Micorrizas/crescimento & desenvolvimento , Microbiologia do Solo , Solo/química , Simbiose , Carbono/metabolismo , Clorofila/análise , Lotus/crescimento & desenvolvimento , Lotus/metabolismo , Micorrizas/metabolismo , Fósforo/metabolismo , Fotossíntese , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Nodulação , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/metabolismo , Rhizobium/crescimento & desenvolvimento , Salinidade , Plantas Tolerantes a Sal/crescimento & desenvolvimento , Plantas Tolerantes a Sal/metabolismo , Plantas Tolerantes a Sal/microbiologia , Sódio/metabolismo , Esporos Fúngicos/metabolismoRESUMO
Charles Darwin, like others before him, collected aeolian dust over the Atlantic Ocean and sent it to Christian Gottfried Ehrenberg in Berlin. Ehrenberg's collection is now housed in the Museum of Natural History and contains specimens that were gathered at the onset of the Industrial Revolution. Geochemical analyses of this resource indicated that dust collected over the Atlantic in 1838 originated from the Western Sahara, while molecular-microbiological methods demonstrated the presence of many viable microbes. Older samples sent to Ehrenberg from Barbados almost two centuries ago also contained numbers of cultivable bacteria and fungi. Many diverse ascomycetes, and eubacteria were found. Scanning electron microscopy and cultivation suggested that Bacillus megaterium, a common soil bacterium, was attached to historic sand grains, and it was inoculated onto dry sand along with a non-spore-forming control, the Gram-negative soil bacterium Rhizobium sp. NGR234. On sand B. megaterium quickly developed spores, which survived for extended periods and even though the numbers of NGR234 steadily declined, they were still considerable after months of incubation. Thus, microbes that adhere to Saharan dust can live for centuries and easily survive transport across the Atlantic.
Assuntos
Bactérias , Poeira , Fungos , Microbiologia/história , Vento , África Ocidental , Oceano Atlântico , Bacillus megaterium/crescimento & desenvolvimento , Bactérias/classificação , Bactérias/genética , Bactérias/crescimento & desenvolvimento , Barbados , Fungos/classificação , Fungos/genética , Fungos/crescimento & desenvolvimento , História do Século XIX , Viabilidade Microbiana , Minerais/análise , Minerais/química , Rhizobium/crescimento & desenvolvimento , Dióxido de SilícioRESUMO
Nodulation of Medicago sativa (alfalfa) is known to be restricted to Sinorhizobium meliloti and a few other rhizobia that include the poorly characterized isolates related to Rhizobium sp. strain Or191. Distinctive features of the symbiosis between alfalfa and S. meliloti are the marked specificity from the plant to the bacteria and the strict requirement for the presence of sulfated lipochitooligosaccharides (Nod factors [NFs]) at its reducing end. Here, we present evidence of the presence of a functional nodH-encoded NF sulfotransferase in the Or191-like rhizobia. The nodH gene, present in single copy, maps to a high molecular weight megaplasmid. As in S. meliloti, a nodF homolog was identified immediately upstream of nodH that was transcribed in the opposite direction (local synteny). This novel nodH ortholog was cloned and shown to restore both NF sulfation and the Nif+Fix+ phenotypes when introduced into an S. meliloti nodH mutant. Unexpectedly, however, nodH disruption in the Or191-like bacteria did not abolish their ability to nodulate alfalfa, resulting instead in a severely delayed nodulation. In agreement with evidence from other authors, the nodH sequence analysis strongly supports the idea that the Or191-like rhizobia most likely represent a genetic mosaic resulting from the horizontal transfer of symbiotic genes from a sinorhizobial megaplasmid to a not yet clearly identified ancestor.
Assuntos
Proteínas de Bactérias/genética , Medicago sativa/microbiologia , Rhizobium/genética , Sulfotransferases/genética , Proteínas de Bactérias/metabolismo , Cromatografia em Camada Fina , Clonagem Molecular , Teste de Complementação Genética , Modelos Genéticos , Dados de Sequência Molecular , Mutação , Filogenia , Raízes de Plantas/microbiologia , Reação em Cadeia da Polimerase , Rhizobium/crescimento & desenvolvimento , Análise de Sequência de DNA , Sulfotransferases/metabolismoRESUMO
An antimicrobial compound was isolated from Azospirillum brasilense culture extracts by high-performance liquid chromatography and further identified by gas chromatography-mass spectrometry as the auxin-like molecule, phenylacetic acid (PAA). PAA synthesis was found to be mediated by the indole-3-pyruvate decarboxylase, previously identified as a key enzyme in indole-3-acetic acid (IAA) production in A. brasilense. In minimal growth medium, PAA biosynthesis by A. brasilense was only observed in the presence of phenylalanine (or precursors thereof). This observation suggests deamination of phenylalanine, decarboxylation of phenylpyruvate, and subsequent oxidation of phenylacetaldehyde as the most likely pathway for PAA synthesis. Expression analysis revealed that transcription of the ipdC gene is upregulated by PAA, as was previously described for IAA and synthetic auxins, indicating a positive feedback regulation. The synthesis of PAA by A. brasilense is discussed in relation to previously reported biocontrol properties of A. brasilense.
Assuntos
Azospirillum brasilense/enzimologia , Carboxiliases/metabolismo , Ácidos Indolacéticos/metabolismo , Fenilacetatos/metabolismo , Azospirillum brasilense/genética , Azospirillum brasilense/crescimento & desenvolvimento , Azospirillum brasilense/metabolismo , Meios de Cultivo Condicionados/química , Erwinia/crescimento & desenvolvimento , Regulação Bacteriana da Expressão Gênica , Testes de Sensibilidade Microbiana , Controle Biológico de Vetores , Fenilacetatos/farmacologia , Fenilalanina/farmacologia , Doenças das Plantas/microbiologia , Pseudomonas syringae/crescimento & desenvolvimento , Rhizobium/crescimento & desenvolvimentoRESUMO
Fifteen isolates from several nodulated tropical legumes from Puerto Rico (USA) were characterised by their phenotypic, molecular and symbiotic features. The identification of isolates was based on a polyphasic approach, including phenotypic characteristics, 16S rRNA sequencing, Low molecular weight (LMW) RNA profiles, Two Primers-RAPD patterns, and restriction patterns from 16S rDNA molecules. Despite of the variety of hosts included in this study the 15 isolates were separated into only two groups that corresponded to Rhizobium gallicum and Rhizobium tropici. This work shows that R. gallicum and R. tropici nodulate legume plants, such as Sesbania, Caliandra, Poitea, Piptadenia, Neptunia and Mimosa species, that were not previously considered as hosts for these rhizobia. Moreover, some of these host plants can be nodulated by both species. The results confirm the great promiscuity of R. tropici and also support the hypothesis that the species R. gallicum may be native from America or cosmopolitan and worldwide spread.
Assuntos
Fabaceae/microbiologia , Fixação de Nitrogênio , Rhizobium tropici/classificação , Rhizobium/classificação , Clima Tropical , Proteínas de Bactérias , DNA Ribossômico/análise , Dados de Sequência Molecular , N-Acetilglucosaminiltransferases/genética , Fenótipo , Polimorfismo de Fragmento de Restrição , Porto Rico , RNA Ribossômico 16S/genética , Técnica de Amplificação ao Acaso de DNA Polimórfico , Rhizobium/genética , Rhizobium/crescimento & desenvolvimento , Rhizobium tropici/genética , Rhizobium tropici/crescimento & desenvolvimento , Análise de Sequência de DNA , SimbioseRESUMO
Cheese whey (CW)-based growth medium efficiently protects Rhizobium loti cells during freezing and desiccation and can maintain their growth in a manner similar to that of traditional mannitol-based medium (YEM). The cheese-whey-based medium (CW) improved viability when used to re-suspend cell pellets kept at -20 degrees C and -80 degrees C and resulted in the survival of over 90% of the cells. Moreover, bacterial pellets obtained from cells grown in CW withstand desiccation better than cells grown in YEM. Survival was over 60% after 30 days at 4 degrees C. No differences were observed in nodulation efficiency between YEM-grown and CW-grown cells. Fast protein liquid chromatography (FPLC) protocols are presented for total protein profile analyses of sweet and acid cheese whey.
Assuntos
Queijo/microbiologia , Microbiologia de Alimentos , Proteínas do Leite/metabolismo , Rhizobium/crescimento & desenvolvimento , Queijo/análise , Dessecação , Fermentação , Lotus/microbiologia , Proteínas do Leite/análise , Proteínas do Leite/química , Rhizobium/fisiologia , Proteínas do Soro do LeiteRESUMO
The plasmid-borne Rhizobium etli katG gene encodes a dual-function catalase-peroxidase (KatG) (EC 1.11.1.7) that is inducible and heat-labile. In contrast to other rhizobia, katG was shown to be solely responsible for catalase and peroxidase activity in R. etli. An R. etli mutant that did not express catalase activity exhibited increased sensitivity to hydrogen peroxide (H(2)O(2)). Pre-exposure to a sublethal concentration of H(2)O(2) allowed R. etli to adapt and survive subsequent exposure to higher concentrations of H(2)O(2). Based on a multiple sequence alignment with other catalase-peroxidases, it was found that the catalytic domains of the R. etli KatG protein had three large insertions, two of which were typical of KatG proteins. Like the katG gene of Escherichia coli, the R. etli katG gene was induced by H(2)O(2) and was important in sustaining the exponential growth rate. In R. etli, KatG catalase-peroxidase activity is induced eightfold in minimal medium during stationary phase. It was shown that KatG catalase-peroxidase is not essential for nodulation and nitrogen fixation in symbiosis with Phaseolus vulgaris, although bacteroid proteome analysis indicated an alternative compensatory mechanism for the oxidative protection of R. etli in symbiosis. Next to, and divergently transcribed from the catalase promoter, an ORF encoding the regulator OxyR was found; this is the first plasmid-encoded oxyR gene described so far. Additionally, the katG promoter region contained sequence motifs characteristic of OxyR binding sites, suggesting a possible regulatory mechanism for katG expression.
Assuntos
Catalase/genética , Proteínas de Ligação a DNA , Plasmídeos , Replicon , Proteínas Repressoras/genética , Rhizobium/enzimologia , Fatores de Transcrição/genética , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Catalase/metabolismo , Regulação Bacteriana da Expressão Gênica , Peróxido de Hidrogênio/farmacologia , Dados de Sequência Molecular , Fixação de Nitrogênio , Phaseolus/microbiologia , Proteínas Repressoras/metabolismo , Rhizobium/genética , Rhizobium/crescimento & desenvolvimento , Análise de Sequência de DNA , Simbiose , Fatores de Transcrição/metabolismoRESUMO
Thirty indigenous rhizobia strains, isolated from Lotus tenuis in the area of Chascomús and other regions of the Salado River Basin (Argentina), were characterized based on generation time, acid production, carbon utilization, protein profile, and molecular characterization by restriction fragment length polymorphism (RFLP) analysis of 16S rRNA genes amplified by the polymerase chain reaction (PCR). The results indicated that native rhizobia isolates from the Chascomús area are predominantly fast and intermediate-growers. The unclassified rhizobia examined by PCR-RFLP were found to be closely related to the reference strains of validly described Rhizobium species.
Assuntos
Lotus/microbiologia , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição , Rhizobium/classificação , Rhizobium/genética , Microbiologia do Solo , Argentina , Proteínas de Bactérias/química , DNA Bacteriano/análise , Genes de RNAr , RNA Ribossômico 16S/genética , Rhizobium/crescimento & desenvolvimento , Rhizobium/isolamento & purificação , SimbioseRESUMO
A defined insertion mutant of a gene encoding a homolog of the rhizobial C4-dicarboxylate permease (dctA) was constructed in Rhizobium tropici strain CIAT899. This mutant (GA1) was unable to grow on fumarate or malate; however, in contrast with other rhizobial dctA mutants, it retained a limited ability to grow on succinate with ammonia as a nitrogen source. Our results suggest the presence of a novel succinate-specific transport system in R. tropici. Biochemical characterization indicated that this alternative transport system in GAI is active and dependent on an energized membrane. It was also induced by succinate and aspartate, and was repressed by glucose and glycerol. Bean plants inoculated with GA1 showed a reduced nitrogen-fixing ability, achieving only 29% of the acetylene reduction activity determined in CIAT899 strain nodules, 33 days after inoculation. Also, bean plants inoculated with GA1 had reduced shoot dry weight compared with plants inoculated with the wild-type strain.
Assuntos
Proteínas de Bactérias/genética , Transportadores de Ácidos Dicarboxílicos/genética , Ácidos Dicarboxílicos/metabolismo , Mutação , Rhizobium/crescimento & desenvolvimento , Ácido Succínico/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/metabolismo , Sequência de Bases , Transporte Biológico , Transportadores de Ácidos Dicarboxílicos/metabolismo , Fabaceae/microbiologia , Dados de Sequência Molecular , Rhizobium/genética , Análise de Sequência de DNA , SimbioseRESUMO
The expression of the pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase (GDH) of Rhizobium tropici CIAT899 and Sinorhizobium meliloti RCR2011 was investigated under different nutrient-limiting conditions in continuous cultures, under different conditions of phosphate availability, and in S. meliloti bacteroids. The presence of free PQQ in alfalfa root exudates has also been assayed. It was shown that apo-GDH or holoenzyme was actively synthesized by these rhizobia, with the concomitant production of gluconate from glucose, under certain environmental conditions. GDH activity was also detected in bacteroids from alfalfa root nodules inoculated with either S. meliloti RCR2011 or 102F34. It was also shown that free PQQ was present in root exudates of alfalfa, but its production is ascribed to the activity of Erwinia sp., a normal contaminant of these seeds.
Assuntos
Glucose Desidrogenase/metabolismo , Glucose/metabolismo , Periplasma/enzimologia , Rhizobium/enzimologia , Sinorhizobium meliloti/enzimologia , Simbiose , Meios de Cultura , Medicago sativa/microbiologia , Oxirredução , Cofator PQQ , Raízes de Plantas/química , Raízes de Plantas/microbiologia , Quinolonas/análise , Quinonas/análise , Rhizobium/crescimento & desenvolvimento , Sinorhizobium meliloti/crescimento & desenvolvimentoRESUMO
Many animal-pathogenic bacteria can use heme compounds as iron sources. Like these microorganisms, rhizobium strains interact with host organisms where heme compounds are available. Results presented in this paper indicate that the use of hemoglobin as an iron source is not restricted to animal-pathogenic microorganisms. We also demonstrate that heme, hemoglobin, and leghemoglobin can act as iron sources under iron-depleted conditions for Rhizobium meliloti 242. Analysis of iron acquisition mutant strains indicates that siderophore-, heme-, hemoglobin-, and leghemoglobin-mediated iron transport systems expressed by R. meliloti 242 share at least one component.
Assuntos
Heme/metabolismo , Hemoglobinas/metabolismo , Ferro/metabolismo , Leghemoglobina/metabolismo , Rhizobium/crescimento & desenvolvimento , Sinorhizobium meliloti/crescimento & desenvolvimento , Animais , Bactérias/crescimento & desenvolvimento , Bactérias/patogenicidade , Transporte Biológico , Bovinos , Meios de Cultura , Etilenodiaminas , Quelantes de Ferro , Rhizobiaceae/crescimento & desenvolvimento , Especificidade da EspécieRESUMO
Native strains of Rhizobium were selected from a chickpea growing area with the purpose of producing inoculants tolerant to environmental conditions of the province of Córdoba. The strains were selected for nitrogen fixing capacity and specificity with four plant genotypes using the following parameters: number of nodules, plant biomass and nitrogen content. Native population of Rhizobium spp in the province of Córdoba showed better competition ability than foreign strains with similar response to different plant genotypes.
Assuntos
Fabaceae/microbiologia , Plantas Medicinais , Rhizobium/fisiologia , Microbiologia do Solo , Argentina , Biomassa , Fabaceae/genética , Genótipo , Humanos , Fixação de Nitrogênio , Rhizobium/classificação , Rhizobium/crescimento & desenvolvimento , Rhizobium/isolamento & purificação , Especificidade da EspécieRESUMO
Pyruvate carboxylase (PYC) is a biotin-dependent enzyme catalyzing the anaplerotic conversion of pyruvate to oxaloacetate in Rhizobium etli strain CE3. A pyc::Tn5 mutant had severely reduced growth, or failed to grow on sugars, three-carbon organic acids or glycerol, consistent with these substrates being metabolized via pyruvate. Transconjugants expressing a pyc::beta-glucuronidase gene fusion had slightly increased apparent pyc transcription during growth on pyruvate as compared to succinate, similar to the modest carbon source dependent changes in PYC activity reported previously. Biotin supplementation of cultures growing on pyruvate dramatically increased PYC activity but not apparent pyc transcription. Bacteroids isolated from bean nodules did not contain detectable PYC activity while apparent pyc transcription occurred at a moderate level.
Assuntos
Proteínas de Bactérias/biossíntese , Regulação Bacteriana da Expressão Gênica , Regulação Enzimológica da Expressão Gênica , Piruvato Carboxilase/biossíntese , Rhizobium/enzimologia , Proteínas de Bactérias/genética , Biotina/farmacologia , Metabolismo dos Carboidratos , Indução Enzimática/efeitos dos fármacos , Fabaceae/microbiologia , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Glicerol/metabolismo , Plantas Medicinais , Piruvato Carboxilase/genética , Ácido Pirúvico/metabolismo , Rhizobium/crescimento & desenvolvimento , Transcrição Gênica/efeitos dos fármacosRESUMO
The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) produced a deleterious effect on the growth of Rhizobium sp. M4, that was reversed by transferring the cells to a fresh control medium. The uptake of 2,4-D by Rhizobium sp. was not affected by chloramphenicol, indicating that it is constitutive rather than inducible. The mechanism of transport also appears to be energy independent, since uptake was not inhibited by azide or arsenate.