RESUMEN
Peanut production could be increased through plant growth-promoting rhizobacteria (PGPR). In this regard, the present field research aimed at elucidating the impact of PGPR on peanut yield, soil enzyme activity, microbial diversity, and structure. Three PGPR strains (Bacillus velezensis, RI3; Bacillus velezensis, SC6; Pseudomonas psychrophila, P10) were evaluated, along with Bradyrhizobium japonicum (BJ), taken as a control. PGPR increased seed yield by 8%, improving the radiation use efficiency (4-14%). PGPR modified soil enzymes (fluorescein diacetate activity by 17% and dehydrogenase activity by 28%) and microbial abundance (12%). However, PGPR did not significantly alter microbial diversity; nonetheless, it modified the relative abundance of key phyla (Actinobacteria > Proteobacteria > Firmicutes) and genera (Bacillus > Arthrobacter > Pseudomonas). PGPRs modified the relative abundance of genes associated with N-fixation and nitrification while increasing genes related to N-assimilation and N-availability. PGPR improved agronomic traits without altering rhizosphere diversity.
Asunto(s)
Arachis , Bacillus , Bradyrhizobium , Metagenómica , Pseudomonas , Rizosfera , Microbiología del Suelo , Suelo , Arachis/microbiología , Arachis/crecimiento & desarrollo , Arachis/metabolismo , Arachis/genética , Bacillus/genética , Bacillus/metabolismo , Bradyrhizobium/genética , Bradyrhizobium/metabolismo , Bradyrhizobium/crecimiento & desarrollo , Bradyrhizobium/fisiología , Pseudomonas/genética , Pseudomonas/fisiología , Pseudomonas/crecimiento & desarrollo , Suelo/química , Producción de Cultivos/métodos , Bacterias/genética , Bacterias/clasificación , Bacterias/metabolismo , Bacterias/enzimología , Bacterias/aislamiento & purificación , Biodiversidad , Fijación del Nitrógeno , Raíces de Plantas/microbiología , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/metabolismoRESUMEN
Environments co-contaminated with heavy metals and hydrocarbons have become an important problem worldwide, especially due to the effect of metals on hydrocarbon degrading microorganisms. Pseudomonas extremaustralis, a bacterium isolated from a pristine pond in Antarctica, showed high capabilities to cope with environmental stress and a very versatile metabolism that includes alkane degradation under microaerobic conditions. In this work, we analyzed P. extremaustralis' capability to resist high copper concentrations and the effect of copper presence in diesel biodegradation. We observed that P. extremaustralis resisted up to 4 mM CuSO4 in a rich medium such as LB. This copper resistance is sustained by the presence of the cus and cop operons together with other efflux systems and porins located in a single region in P. extremaustralis genome. When copper was present, diesel degradation was negatively affected, even though copper enhanced bacterial attachment to hydrocarbons. However, when a small amount of glucose (0.05% w/v) was added, the presence of CuSO4 enhanced alkane degradation. In addition, atomic force microscopy analysis showed that the presence of glucose decreased the negative effects produced by copper and diesel on the cell envelopes.
Asunto(s)
Cobre/metabolismo , Contaminantes Ambientales/metabolismo , Gasolina/microbiología , Pseudomonas/metabolismo , Biodegradación Ambiental , Operón , Porinas/metabolismo , Pseudomonas/genética , Pseudomonas/crecimiento & desarrolloRESUMEN
Abstract Mathematical models are often used to predict microbial growth in food products. An important class of these models involves the adaptation of classical sigmoid functions, such as the Gompertz and logistic functions. This study aimed to validate the use of the modified Richards model in various situations, which have not previously been tested. The model was obtained through solving a system of two differential equations and could be applied to both isothermal and non-isothermal environments. To test and validate this model, we used published datasets containing data for the growth of Pseudomonas spp. in fish products. The results obtained after fitting the model showed that it could be effectively used to describe and predict the Pseudomonas growth curves under various temperature regimens. However, the influence of the shape parameter on the growth curve is an issue that needs further evaluation.
Asunto(s)
Animales , Pseudomonas/crecimiento & desarrollo , Cinética , Pseudomonas/química , Temperatura , Productos Pesqueros/microbiología , Modelos TeóricosRESUMEN
Siderophores are low-molecular weight ligands secreted by bacteria as a survival strategy in Fe(III)-lacking environments. They bind not only Fe(III), but Co(II), Zn(II), Mn(II), Ni(II), Ga(III) as a detoxification alternative. The synthesis, purification and characterization of siderophores produced by Pseudomonas veronii 2E were evaluated to be applied in future environmental technologies. Optimal production was obtained in Fe(III)-free M9-succinate at 25 °C, 40 h and pH 6.9. Siderophores were chemically characterized as hydroxamate and catechol mixed-type. Spectroscopic analysis indicated their belonging to the pyoverdine family, behaving as ligand to Cd(II), Zn(II), Cu(II), Ni(II) and Cr(III), which promoted siderophoregenesis during growth. Siderophore-Cd(II) complexation was studied by electrochemical monitored titration revealing one family of moderate-strength binding sites. Mass spectral analysis evidenced the secretion of a variety of molecules (molecular mass ca.1200 u). Non pathogenic Pseudomonas veronii 2E siderophores represent a safe alternative for the concrete application of environmental technologies and clinical procedures.
Asunto(s)
Pseudomonas/metabolismo , Sideróforos/biosíntesis , Sideróforos/química , Sideróforos/aislamiento & purificación , Compuestos Férricos , Concentración de Iones de Hidrógeno , Quelantes del Hierro , Ligandos , Espectrometría de Masas , Metales/farmacología , Oligopéptidos/química , Pseudomonas/efectos de los fármacos , Pseudomonas/crecimiento & desarrolloRESUMEN
Mathematical models are often used to predict microbial growth in food products. An important class of these models involves the adaptation of classical sigmoid functions, such as the Gompertz and logistic functions. This study aimed to validate the use of the modified Richards model in various situations, which have not previously been tested. The model was obtained through solving a system of two differential equations and could be applied to both isothermal and non-isothermal environments. To test and validate this model, we used published datasets containing data for the growth of Pseudomonas spp. in fish products. The results obtained after fitting the model showed that it could be effectively used to describe and predict the Pseudomonas growth curves under various temperature regimens. However, the influence of the shape parameter on the growth curve is an issue that needs further evaluation.
Asunto(s)
Productos Pesqueros/microbiología , Pseudomonas/crecimiento & desarrollo , Animales , Cinética , Modelos Teóricos , Pseudomonas/química , TemperaturaRESUMEN
Bacteria isolated from soil and rhizosphere samples collected in Peru from Andean crops were tested in vitro and in vivo to determine their potential as plant growth promoters and their ability to induce systemic resistance to Alternaria alternata in tomato plants. The isolates were identified by sequencing their 16S ribosomal RNA gene. Test for phosphate solubilization, and indolacetic acid were also carried out, together with in vitro antagonism assays in dual cultures towards the plant pathogens Fusarium solani, A. alternata and Curvularia lunata. The three most promising isolates (Pa15, Ps155, Ps168) belonged to the genus Pseudomonas. Further assays were carried out with tomato plants to assess their plant protection effect towards A. alternata and as growth promoters. Inoculation of tomato seeds with all isolates significantly enhanced seed germination, plantlets emergence and plant development. Bacterial inoculation also reduce damage level caused by A. alternata. The expression levels of three tomato genes involved in the jasmonate (AOS), ethylene responsive (ERF-2) and pathogenesis related (PR-P2) pathways were determined in plants challenged with A. alternata, alone or with each bacterial isolate, respectively. Results showed that at 24 h after infection, in absence of the pathogen, the expression level of the tested genes was very low. The presence of A. alternata alone and in combination with bacteria increased the transcripts of all genes. Data showed a potential of best performing isolate Ps168 to sustain tomato plants nutrition and activate defense-related genes for protection by pathogenic fungi.
Asunto(s)
Pseudomonas/crecimiento & desarrollo , Pseudomonas/aislamiento & purificación , Solanum lycopersicum/crecimiento & desarrollo , Solanum lycopersicum/microbiología , Productos Agrícolas/genética , Productos Agrícolas/crecimiento & desarrollo , Productos Agrícolas/microbiología , Resistencia a la Enfermedad , Regulación de la Expresión Génica de las Plantas , Germinación , Solanum lycopersicum/genética , Perú , Desarrollo de la Planta , Enfermedades de las Plantas/prevención & control , Pseudomonas/clasificación , Pseudomonas/genética , Rizosfera , Microbiología del SueloRESUMEN
Alginate is a linear polysaccharide that can be used for different applications in the food and pharmaceutical industries. These polysaccharides have a chemical structure composed of subunits of (1-4)-ß-D-mannuronic acid (M) and its C-5 epimer α-L-guluronic acid (G). The monomer composition and molecular weight of alginates are known to have effects on their properties. Currently, these polysaccharides are commercially extracted from seaweed but can also be produced by Azotobacter vinelandii and Pseudomonas spp. as an extracellular polymer. One strategy to produce alginates with different molecular weights and with reproducible physicochemical characteristics is through the manipulation of the culture conditions during fermentation. This mini-review provides a comparative analysis of the metabolic pathways and molecular mechanisms involved in alginate polymerization from A. vinelandii and Pseudomonas spp. Different fermentation strategies used to produce alginates at a bioreactor laboratory scale are described.
Asunto(s)
Alginatos/metabolismo , Azotobacter vinelandii/crecimiento & desarrollo , Pseudomonas/crecimiento & desarrollo , Alginatos/química , Azotobacter vinelandii/genética , Azotobacter vinelandii/metabolismo , Reactores Biológicos , Fermentación , Ácido Glucurónico/química , Ácido Glucurónico/metabolismo , Ácidos Hexurónicos/química , Ácidos Hexurónicos/metabolismo , Redes y Vías Metabólicas , Peso Molecular , Pseudomonas/genética , Pseudomonas/metabolismoRESUMEN
Background: In recent years, Antarctica has become a key source of biotechnological resources. Native microorganisms have developed a wide range of survival strategies to adapt to the harsh Antarctic environment, including the formation of biofilms. Alginate is the principal component of the exopolysaccharide matrix in biofilms produced by Pseudomonas, and this component is highly demanded for the production of a wide variety of commercial products. There is a constant search for efficient alginate-producing organisms. Results: In this study, a novel strain of Pseudomonas mandelii isolated from Antarctica was characterized and found to overproduce alginate compared with other good alginate producers such as Pseudomonas aeruginosa and Pseudomonas fluorescens. Alginate production and expression levels of the alginate operon were highest at 4°C. It is probable that this alginate-overproducing phenotype was the result of downregulated MucA, an anti-sigma factor of AlgU. Conclusion: Because biofilm formation is an efficient bacterial strategy to overcome stressful conditions, alginate overproduction might represent the best solution for the successful adaptation of P. mandelii to the extreme temperatures of the Antarctic. Through additional research, it is possible that this novel P. mandelii strain could become an additional source for biotechnological alginate production.
Asunto(s)
Pseudomonas/metabolismo , Alginatos/metabolismo , Polisacáridos Bacterianos/metabolismo , Pseudomonas/crecimiento & desarrollo , Pseudomonas/genética , Adaptación Biológica , Frío , Microscopía Confocal , Biopelículas , Phaeophyceae , Tipificación de Secuencias Multilocus , Reacción en Cadena en Tiempo Real de la Polimerasa , Regiones AntárticasRESUMEN
Plant-growth-promoting bacteria belonging to Azospirillum and Pseudomonas genera are major inhabitants of the rhizosphere. Both are increasingly commercialized as crops inoculants. Interspecific interaction in the rhizosphere is critical for inoculants aptness. The objective of this work was to evaluate Azospirillum and Pseudomonas interaction in mixed biofilms by co-cultivation of the model strains Azospirillum brasilense Sp245 and Pseudomonas protegens CHA0. The results revealed enhanced growth of both strains when co-cultured in static conditions. Moreover, Sp245 biofilm formed in plastic surfaces was increased 2-fold in the presence of CHA0. Confocal microscopy revealed highly structured mixed biofilms showing Sp245 mainly on the bottom and CHA0 towards the biofilm surface. In addition, A. brasilense biofilm was thicker and denser when co-cultured with P. protegens. In a colony-colony interaction assay, Sp245 changed nearby CHA0 producing small colony phenotype, which accounts for a diffusible metabolite mediator; though CHA0 spent medium did not affect Sp245 colony phenotype. Altogether, these results point to a cooperative interaction between A. brasilense Sp245 and P. protegens CHA0 in which both strains increase their static growth and produce structured mixed biofilms with a strain-specific distribution.
Asunto(s)
Azospirillum brasilense/crecimiento & desarrollo , Biopelículas/crecimiento & desarrollo , Plantas/microbiología , Pseudomonas/crecimiento & desarrollo , Microbiología del Suelo , Azospirillum brasilense/metabolismo , Técnicas de Cocultivo , Raíces de Plantas/microbiología , Pseudomonas/metabolismo , RizosferaRESUMEN
The biotechnology sector is continually seeking sustainable and more economical bioprocesses. Fermentation media produced with cheap components or wastes reduce production costs. Moreover, if wastes are used, they contribute to avoid environmental pollution. In this work, microbial growth media based on molasses or acidified glycerol as carbon sources and fertilizer as nitrogen source were tested for the production of a whole-cell catalyst that could be used in Cr(VI)-containing wastewater treatments. Results showed that the highest biomass production yield was obtained with a medium containing acidified glycerol 5% v/v and fertilizer 0.6% v/v. The biomass produced using this medium was immobilized in calcium alginate beads and used as catalyst in the biotransformation of Cr(VI) into Cr(III). The catalyst could be efficiently used for 5 reduction cycles of 40mg/l Cr(VI) each. Cr(III) retention assays were performed to determine whether Cr(III) could be retained by the catalyst avoiding its solubilization in the supernatants. The retention capacity of the catalyst at 32°C and pH 3.0 was 3mg Cr(III)/g. Both an alternative and economical fermentation medium is here proposed for the optimization of Cr(VI)-containing wastewater treatment.
Asunto(s)
Biodegradación Ambiental , Cromo/metabolismo , Medios de Cultivo , Fermentación , Pseudomonas/efectos de los fármacos , Aguas Residuales/química , Contaminantes Químicos del Agua/metabolismo , Purificación del Agua/métodos , Biomasa , Carbono/metabolismo , Catálisis , Células Inmovilizadas , Cromo/análisis , Medios de Cultivo/economía , Medios de Cultivo/farmacología , Fertilizantes , Glicerol/economía , Glicerol/farmacología , Indicadores y Reactivos/economía , Melaza , Nitrógeno/metabolismo , Pseudomonas/crecimiento & desarrollo , Pseudomonas/metabolismo , Solubilidad , Aguas Residuales/economía , Contaminantes Químicos del Agua/análisis , Purificación del Agua/economíaRESUMEN
Polychlorinated biphenyls (PCBs), the chlorinated derivatives of biphenyl, are one of the most prevalent, highly toxic and persistent groups of contaminants in the environment. The objective of this study was to investigate the biodegradation of PCBs in northeastern (Heilongjiang Province), northern (Shanxi Province) and eastern China (Shanghai municipality). From these areas, nine soil samples were screened for PCB-degrading bacteria using a functional complementarity method. The genomic 16S rDNA locus was amplified and the products were sequenced to identify the bacterial genera. Seven Pseudomonas strains were selected to compare the capacity of bacteria from different regions to degrade biphenyl by HPLC. Compared to the biphenyl content in controls of 100%, the biphenyl content went down to 3.7% for strain P9-324, 36.3% for P2-11, and 20.0% for the other five strains. These results indicate that a longer processing time led to more degradation of biphenyl. PCB-degrading bacterial strains are distributed differently in different regions of China.(AU)
Asunto(s)
Compuestos de Bifenilo/química , Compuestos de Bifenilo/síntesis química , Biodegradación Ambiental , Pseudomonas/clasificación , Pseudomonas/crecimiento & desarrolloRESUMEN
The perfluorooctanoic acid (PFOA)-degrading strain YAB1 was isolated from the soil near a perfluorinated compound production plant through acclimation and enrichment culture, using PFOA as the sole carbon source. This strain was preliminarily identified as Pseudomonas parafulva based on colony morphology, physiological and biochemical features, and 16S rRNA gene sequencing. Using shaking flask fermentation, the maximum tolerable concentration of YAB1 on PFOA was found to be 1000 mg/L. The optimal conditions for bacterial growth and PFOA degradation were 30°C, pH 7, 2% inoculum, and an initial PFOA concentration of 500 mg/L. After 96 h of culture, the PFOA degradation rate determined by GC-MS analysis was 32.4%. When 1 g/L glucose was added to the inorganic salt culture medium, the degradation rate increased to 48.1%. Glucose was the best exogenous carbon source for the degradation of PFOA. This study reports the degradation performance of PFOA-degrading bacteria.
Asunto(s)
Caprilatos/metabolismo , Fermentación , Fluorocarburos/metabolismo , Pseudomonas/metabolismo , Biodegradación Ambiental , Glucosa/metabolismo , Pseudomonas/genética , Pseudomonas/crecimiento & desarrollo , Pseudomonas/aislamiento & purificación , ARN Ribosómico 16S/genética , Microbiología del SueloRESUMEN
A Burkholderia and Pseudomonas species designated as AB4 and AS1, respectively, were isolated from soil containing decomposing straw or sugar cane bagasse collected from Brazil. This study sought to evaluate the capacities of culture media, cell-free medium, and crude lysate preparations (containing PHB inclusion bodies) from bacterial cell cultures to stabilize emulsions with several hydrophobic compounds. Four conditions showed good production of bioemulsifiers (E24 ≥ 50 %), headed by substantially cell-free media from bacterial cell cultures in which bacterial isolates from Burkholderia sp. strain AB4 and Pseudomonas sp. strain AS1 were grown. Our results revealed that the both isolates (AB4 and AS1 strains) exhibited high emulsification indices (indicating usefulness in bioremediation) and good stabilities.
Asunto(s)
Burkholderia/metabolismo , Emulsiones , Glucosa/metabolismo , Polihidroxialcanoatos/metabolismo , Pseudomonas/metabolismo , Biomasa , Burkholderia/crecimiento & desarrollo , Pseudomonas/crecimiento & desarrolloRESUMEN
Mercury salts and tellurite are among the most toxic compounds for microorganisms on Earth. Bacterial mercury resistance is established mainly via mercury reduction by the mer operon system. However, specific mechanisms underlying tellurite resistance are unknown to date. To identify new mechanisms for tellurite detoxification we demonstrate that mercury resistance mechanisms can trigger cross-protection against tellurite to a group of Pseudomonads isolated from the Chilean Antarctic territory. Sequencing of 16S rRNA of four isolated strains resulted in the identification of three Pseudomonads (ATH-5, ATH-41 and ATH-43) and a Psychrobacter (ATH-62) bacteria species. Phylogenetic analysis showed that ATH strains were related to other species previously isolated from cold aquatic and soil environments. Furthermore, the identified merA genes were related to merA sequences belonging to transposons commonly found in isolated bacteria from mercury contaminated sites. Pseudomonas ATH isolates exhibited increased tellurite resistance only in the presence of mercury, especially ATH-43. Determination of the growth curves, minimal inhibitory concentrations and growth inhibition zones showed different tellurite cross-resistance of the ATH strains and suggested a correlation with the presence of a mer operon. On the other hand, reactive oxygen species levels decreased while the thiol content increased when the isolates were grown in the presence of both toxicants. Finally, qPCR determinations of merA, merC and rpoS transcripts from ATH-43 showed a synergic expression pattern upon combined tellurite and mercury treatments. Altogether, the results suggest that mercury could trigger a cell response that confers mercury and tellurite resistance, and that the underlying mechanism participates in protection against oxidative damage.
Asunto(s)
Mercurio/toxicidad , Pseudomonas/efectos de los fármacos , Pseudomonas/aislamiento & purificación , Telurio/toxicidad , Regiones Antárticas , Chile , Regulación Bacteriana de la Expresión Génica/efectos de los fármacos , Geografía , Pruebas de Sensibilidad Microbiana , Fenotipo , Filogenia , Pseudomonas/genética , Pseudomonas/crecimiento & desarrollo , Especies Reactivas de Oxígeno/metabolismo , Reacción en Cadena en Tiempo Real de la Polimerasa , Compuestos de Sulfhidrilo/metabolismoRESUMEN
Growth curves were evaluated for aerobic mesophilic and psychrotrophic bacteria, Pseudomonas spp. and Staphylococcus spp., grown in raw, salted, and cooked chicken breast at 2, 4, 7, 10, 15, and 20 â, respectively, using the modified Gompertz and modified logistic models. Shelf life was determined based on microbiological counts and sensory analysis. Temperature increase reduced the shelf life, which varied from 10 to 26 days at 2 â, from nine to 21 days at 4 â, from six to 12 days at 7 â, from four to eight days at 10 â, from two to four days at 15 â, and from one to two days at 20 â. In most cases, cooked chicken breast showed the highest microbial count, followed by raw breast and lastly salted breast. The data obtained here were useful for the generation of mathematical models and parameters. The models presented high correlation and can be used for predictive purposes in the poultry meat supply chain.
Asunto(s)
Pollos/microbiología , Culinaria/métodos , Microbiología de Alimentos/métodos , Almacenamiento de Alimentos/métodos , Pseudomonas/crecimiento & desarrollo , Cloruro de Sodio , Staphylococcus/crecimiento & desarrollo , Animales , Recuento de Colonia Microbiana , Microbiología de Alimentos/estadística & datos numéricos , Conservación de Alimentos/métodos , Calidad de los Alimentos , Humanos , Pigmentos Biológicos , Olfato , Gusto , TemperaturaRESUMEN
Temperature is one of the most important factors for bacterial growth and development. Cold environments are widely distributed on earth, and psychrotolerant and psychrophilic microorganisms have developed different adaptation strategies to cope with the stress derived from low temperatures. Pseudomonas extremaustralis is an Antarctic bacterium able to grow under low temperatures and to produce high amounts of polyhydroxyalkanoates (PHAs). In this work, we analyzed the genome-wide transcriptome by RNA deep-sequencing technology of early exponential cultures of P. extremaustralis growing in LB (Luria Broth) supplemented with sodium octanoate to favor PHA accumulation at 8°C and 30°C. We found that genes involved in primary metabolism, including tricarboxylic acid cycle (TCA) related genes, as well as cytochromes and amino acid metabolism coding genes, were repressed at low temperature. Among up-regulated genes, those coding for transcriptional regulatory and signal transduction proteins were over-represented at cold conditions. Remarkably, we found that genes involved in ethanol oxidation, exaA, exaB and exaC, encoding a pyrroloquinoline quinone (PQQ)-dependent ethanol dehydrogenase, the cytochrome c550 and an aldehyde dehydrogenase respectively, were up-regulated. Along with RNA-seq experiments, analysis of mutant strains for pqqB (PQQ biosynthesis protein B) and exaA were carried out. We found that the exaA and pqqB genes are essential for growth under low temperature in LB supplemented with sodium octanoate. Additionally, p-rosaniline assay measurements showed the presence of alcohol dehydrogenase activity at both 8°C and 30°C, while the activity was abolished in a pqqB mutant strain. These results together with the detection of ethanol by gas chromatography in P. extremaustralis cultures grown at 8°C support the conclusion that this pathway is important under cold conditions. The obtained results have led to the identification of novel components involved in cold adaptation mechanisms in this bacterium, suggesting for the first time a role of the ethanol oxidation pathway for bacterial growth at low temperatures.
Asunto(s)
Frío , Etanol/metabolismo , Perfilación de la Expresión Génica , Genes Bacterianos , Pseudomonas/genética , Alcohol Deshidrogenasa/metabolismo , Regiones Antárticas , Regulación Bacteriana de la Expresión Génica , Sistemas de Lectura Abierta/genética , Oxidación-Reducción , Pseudomonas/crecimiento & desarrollo , Programas Informáticos , Regulación hacia Arriba/genéticaRESUMEN
Pseudomonas protegens strain Pf-5 is a rhizosphere bacterium that suppresses soilborne plant diseases and produces at least seven different secondary metabolites with antifungal properties. We derived mutants of Pf-5 with single and multiple mutations in biosynthesis genes for seven antifungal metabolites: 2,4-diacetylphoroglucinol (DAPG), pyrrolnitrin, pyoluteorin, hydrogen cyanide, rhizoxin, orfamide A, and toxoflavin. These mutants were tested for inhibition of the pathogens Fusarium verticillioides and Fusarium oxysporum f. sp. pisi. Rhizoxin, pyrrolnitrin, and DAPG were found to be primarily responsible for fungal antagonism by Pf-5. Previously, other workers showed that the mycotoxin fusaric acid, which is produced by many Fusarium species, including F. verticillioides, inhibited the production of DAPG by Pseudomonas spp. In this study, amendment of culture media with fusaric acid decreased DAPG production, increased pyoluteorin production, and had no consistent influence on pyrrolnitrin or orfamide A production by Pf-5. Fusaric acid also altered the transcription of biosynthetic genes, indicating that the mycotoxin influenced antibiotic production by Pf-5 at the transcriptional level. Addition of fusaric acid to the culture medium reduced antibiosis of F. verticillioides by Pf-5 and derivative strains that produce DAPG but had no effect on antibiosis by Pf-5 derivatives that suppressed F. verticillioides due to pyrrolnitrin or rhizoxin production. Our results demonstrated the importance of three compounds, rhizoxin, pyrrolnitrin, and DAPG, in suppression of Fusarium spp. by Pf-5 and confirmed that an interspecies signaling system mediated by fusaric acid had parallel effects on antifungal metabolite production and antibiosis by the bacterial biological control organism.
Asunto(s)
Antibiosis , Antifúngicos/metabolismo , Ácido Fusárico/metabolismo , Fusarium/efectos de los fármacos , Interacciones Microbianas , Pseudomonas/efectos de los fármacos , Transducción de Señal , Medios de Cultivo/química , Fusarium/crecimiento & desarrollo , Fusarium/metabolismo , Redes y Vías Metabólicas/efectos de los fármacos , Pseudomonas/crecimiento & desarrollo , Pseudomonas/metabolismo , Transcripción GenéticaRESUMEN
Salinity is the leading abiotic stress hampering maize ( Zea mays L.) growth throughout the world, especially in Pakistan. During salinity stress, the endogenous ethylene level in plants increases, which retards proper root growth and consequent shoot growth of the plants. However, certain bacteria contain the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, which converts 1-aminocyclopropane-1-carboxylic acid (an immediate precursor of ethylene biosynthesis in higher plants) into ammonia and α-ketobutyrate instead of ethylene. In the present study, two Pseudomonas bacterial strains containing ACC-deaminase were tested separately and in combinations with mineral fertilizers to determine their potential to minimize/undo the effects of salinity on maize plants grown under saline-sodic field conditions. The data recorded at 30, 50 and 70 days after sowing revealed that both the Pseudomonas bacterial strains improved root and shoot length, root and shoot fresh weight, and root and shoot dry weight up to 34, 43, 35, 71, 55 and 68%, respectively, when applied without chemical fertilizers: these parameter were enhanced up to 108, 95, 100, 131, 100 and 198%, respectively, when the strains were applied along with chemical fertilizers. It can be concluded that ACC-deaminase Pseudomonas bacterial strains applied alone and in conjunction with mineral fertilizers improved the root and shoot growth of maize seedlings grown in saline-sodic soil.
Asunto(s)
Desarrollo de la Planta , Raíces de Plantas/fisiología , Brotes de la Planta/fisiología , Pseudomonas/crecimiento & desarrollo , Microbiología del Suelo , Suelo/química , Zea mays/fisiología , Aminoácidos Cíclicos/metabolismo , Amoníaco/metabolismo , Butiratos , Liasas de Carbono-Carbono/metabolismo , Fertilizantes , Pakistán , Pseudomonas/enzimología , SalinidadRESUMEN
En contraste con la simbiosis entre rizobios y leguminosas, la especificidad de las Pseudomonas en la colonización radicular parece menos estricta. Sin embargo, estudios sobre la diversidad bacteriana del nicho rizosférico resaltan la influencia de la especie vegetal en la selección específica de ciertos microorganismos a partir de la flora residente del suelo. Para evaluar el efecto que los cultivos extensivos de nuestro país tienen sobre la estructura de las comunidades de Pseudomonas, se realizaron experimentos con plantas trampa, partiendo de semillas de trigo, maíz y soja desinfectadas superficialmente y sembradas en un mismo suelo prístino. A partir de las suspensiones representativas de la microflora del rizoplano, se realizaron recuentos en placa en medio selectivo para Pseudomonas. El conjunto de colonias originado a partir de los distintos rizoplanos se utilizó como fuente de ADN para analizar la estructura de comunidad a través del perfil de restricción de amplicones de los genes oprF y gacA. El análisis comparativo de estos perfiles agrupó a las muestras por especie de planta y las distinguió del patrón obtenido a partir del suelo prístino. La secuenciación parcial del gen 16S ADNr de aislamientos bacterianos representativos confirmó la existencia de genotipos enriquecidos diferencialmente en el rizoplano de cada especie vegetal. Estos resultados apoyan la hipótesis de la existencia de mecanismos de selección específica de estirpes de Pseudomonas a partir de la flora nativa del suelo en la interacción cooperativa entre estas PGPR y las raíces de diferentes cultivos como trigo, soja y maíz
In contrast to rhizobia-legume symbiosis, the specificity for root colonization by pseudomonads seems to be less strict. However, several studies about bacterial diversity in the rhizosphere highlight the influence of plant species on the selective enrichment of certain microorganisms from the bulk soil community. In order to evaluate the effect that different crops have on the structure of pseudomonad community on the root surface, we performed plant trap experiments, using surface-disinfected maize, wheat or soybean seeds that were sown in pots containing the same pristine soil as substrate. Rhizoplane suspensions were plated on a selective medium for Pseudomonas, and pooled colonies served as DNA source to carry out PCR-RFLP community structure analysis of the pseudomonads-specific marker genes oprF and gacA. PCR-RFLP profiles were grouped by plant species, and were distinguished from those of bulk soil samples. Partial sequencing of 16S rDNA genes of some representative colonies of Pseudomonas confirmed the selective enrichment of distinctive genotypes in the rhizoplane of each plant species. These results support the idea that the root systems of agricultural crops such as soybean, maize and wheat, select differential sets of pseudomonads from the native microbial repertoire inhabiting the bulk soil
Asunto(s)
Pseudomonas/crecimiento & desarrollo , Semillas/microbiología , ADN Ribosómico/análisis , Rizosfera , GenotipoRESUMEN
Salinity is the leading abiotic stress hampering maize (Zea mays L.) growth throughout the world, especially in Pakistan. During salinity stress, the endogenous ethylene level in plants increases, which retards proper root growth and consequent shoot growth of the plants. However, certain bacteria contain the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, which converts 1-aminocyclopropane-1-carboxylic acid (an immediate precursor of ethylene biosynthesis in higher plants) into ammonia and α-ketobutyrate instead of ethylene. In the present study, two Pseudomonas bacterial strains containing ACC-deaminase were tested separately and in combinations with mineral fertilizers to determine their potential to minimize/undo the effects of salinity on maize plants grown under saline-sodic field conditions. The data recorded at 30, 50 and 70 days after sowing revealed that both the Pseudomonas bacterial strains improved root and shoot length, root and shoot fresh weight, and root and shoot dry weight up to 34, 43, 35, 71, 55 and 68%, respectively, when applied without chemical fertilizers: these parameter were enhanced up to 108, 95, 100, 131, 100 and 198%, respectively, when the strains were applied along with chemical fertilizers. It can be concluded that ACC-deaminase Pseudomonas bacterial strains applied alone and in conjunction with mineral fertilizers improved the root and shoot growth of maize seedlings grown in saline-sodic soil.