RESUMO
The use of products of microbial origin, bacteria, for agriculture has grown exponentially in the world, and in Brazil this growth is significant. In recent years,several companies have settled in the country and started to develop different products in this segment. The producer has the possibility of multiplying bacteria on the farms themselves in a process called on farm, a homemade way of multiplying bacteria. The objective of this studywas to evaluate the efficiency of the mixtures produced through the on farmmethod of multiplication of microorganisms from inoculants based on Azospirillumwith different culture media. For this, three culture media were used: commercial product Multibacter®, yeast syrup plus sugar and yeast syrup, which were subsequently quantified. The syrups were produced in the onfarmsystem, the sterilization of the place of packaging and allocation of the bioreactors was carried out, the samples of the syrups were diluted for incubation and the preparation of the TSA(Trypticasein Soy Agar)also took place. It was possible to conclude that the non-sterile culture media do not present satisfactory results for the multiplication of on farmmicroorganisms with Azospirillumsyrups. Colony forming units are not parameters to indicate viability for non-sterile culture media.(AU)
O uso de produtos de origem microbiana, bactérias, para a agricultura tem crescido exponencialmente no mundo, e no Brasil este crescimento é significativo. Nos últimos anos várias empresas se instalaram no país e passaram a desenvolver diversos produtos neste segmento. O produtor, tem a possibilidade de multiplicar bactérias nas próprias fazendas em um processo chamado on farm,uma forma caseira de multiplicar bactérias. O objetivo deste estudo foi avaliar a eficiência das caldas produzidas através do método on farmde multiplicação de microrganismos de inoculantes a base de Azospirillumcom diferentes meios de culturas. Para isto foram utilizados três meios de cultura: produto comercial Multibacter®, calda de levedura mais açúcar e calda de levedura, os quais posteriormente foram quantificados. As caldas foram produzidas no sistema on farm, foi realizada a esterilização do local acondicionamento e alocação dos biorreatores, as amostras das caldas foram diluídas para incubação e também ocorreu o preparo do TSA (Trypticasein Soy Agar). Foi possível concluir que os meios de cultura não estéreis não apresentam resultados satisfatórios para a multiplicação de microrganismos on farmcom caldas de Azospirillum. Unidades formadoras de colônias não são parâmetros para indicar a viabilidade para meios de cultura não estéreis.(AU)
Assuntos
Azospirillum/crescimento & desenvolvimento , Inoculantes Agrícolas/crescimento & desenvolvimentoRESUMO
The purpose of this study was to evaluate the contribution of the inoculation of the strain Azospirillum MAY12 to the development of rice plants of the cultivar BRS Esmeralda. A completely randomized experiment was performed in a greenhouse, with 8 treatments and 6 repetitions, namely, commercial inoculant (CI) containing strains of Azospirillum brasilense ABV5 and ABV6 (T1), MAY12 (T2), nitrogen control with 50 mg of N or full dose (T3), CI + 30% of N (percentage referring to full dose) (T4), CI + 60% N (T5), MAY12 + 30% N (T6), MAY12 + 60% N (T7) and absolute control (T8). There was a significant increase in the fresh and dry mass of the shoot and roots, height, root volume, and the number of tillers and leaves of plants with the MAY12 inoculation (with and without N added) compared to T8. Treatments containing MAY12 + N increased the total dry mass by ~920% compared to T8, matching the T3 yield. The inoculation of MAY12 in isolation was as efficient as the application of the full dose of N, resulting in an increase of ~115% in height and 373% in root volume of the plants compared to T8. The MAY12 strain demonstrated good performance in the development of the cultivar, which was comparable to the CI in the variables tested. Therefore, inoculation with the MAY12 strain is promising for the partial reduction of nitrogen fertilizers in upland rice cultivation.(AU)
O objetivo deste trabalho foi avaliar a contribuição da inoculação da estirpe de Azospirillum MAY12 no desenvolvimento de plantas de arroz da cultivar BRS Esmeralda. Foi realizado um experimento inteiramente casualizado em casa de vegetação, tendo oito tratamentos e seis repetições: inoculante comercial (IC) contendo as estirpes de Azospirillum brasilense AbV5 e AbV6 (T1), MAY12 (T2), testemunha nitrogenada com 50 mg de N ou dose cheia (T3), IC + 30% de N (percentual referente à dose cheia) (T4), IC + 60% de N (T5), MAY12 + 30% de N (T6), MAY12 + 60% de N (T7) e testemunha absoluta (T8). Houve aumento significativo da massa fresca e seca da parte aérea e de raízes, altura, volume de raízes e do número de perfilhos e de folhas das plantas com a inoculação de MAY12 (com e sem adição de N) em relação a T8. Os tratamentos contendo MAY12 + N aumentaram em torno de 920% a massa seca total em relação a T8, equiparando-se ao rendimento T3. A inoculação de MAY12, isoladamente, foi tão eficiente quanto a aplicação da dose cheia de N para o aumento em torno de 115% da altura e de 373% do volume de raízes das plantas em relação a T8. A estirpe MAY12 apresentou bom desempenho no desenvolvimento da cultivar equiparando-se com o IC nas variáveis testadas. Portanto, a inoculação com a estirpe MAY12 mostra-se promissora para a redução parcial de fertilizantes nitrogenados no cultivo de arroz de terras altas.(AU)
Assuntos
Oryza/crescimento & desenvolvimento , Azospirillum/crescimento & desenvolvimentoRESUMO
The purpose of this study was to evaluate the contribution of the inoculation of the strain Azospirillum MAY12 to the development of rice plants of the cultivar BRS Esmeralda. A completely randomized experiment was performed in a greenhouse, with 8 treatments and 6 repetitions, namely, commercial inoculant (CI) containing strains of Azospirillum brasilense ABV5 and ABV6 (T1), MAY12 (T2), nitrogen control with 50 mg of N or full dose (T3), CI + 30% of N (percentage referring to full dose) (T4), CI + 60% N (T5), MAY12 + 30% N (T6), MAY12 + 60% N (T7) and absolute control (T8). There was a significant increase in the fresh and dry mass of the shoot and roots, height, root volume, and the number of tillers and leaves of plants with the MAY12 inoculation (with and without N added) compared to T8. Treatments containing MAY12 + N increased the total dry mass by ~920% compared to T8, matching the T3 yield. The inoculation of MAY12 in isolation was as efficient as the application of the full dose of N, resulting in an increase of ~115% in height and 373% in root volume of the plants compared to T8. The MAY12 strain demonstrated good performance in the development of the cultivar, which was comparable to the CI in the variables tested. Therefore, inoculation with the MAY12 strain is promising for the partial reduction of nitrogen fertilizers in upland rice cultivation.
O objetivo deste trabalho foi avaliar a contribuição da inoculação da estirpe de Azospirillum MAY12 no desenvolvimento de plantas de arroz da cultivar BRS Esmeralda. Foi realizado um experimento inteiramente casualizado em casa de vegetação, tendo oito tratamentos e seis repetições: inoculante comercial (IC) contendo as estirpes de Azospirillum brasilense AbV5 e AbV6 (T1), MAY12 (T2), testemunha nitrogenada com 50 mg de N ou dose cheia (T3), IC + 30% de N (percentual referente à dose cheia) (T4), IC + 60% de N (T5), MAY12 + 30% de N (T6), MAY12 + 60% de N (T7) e testemunha absoluta (T8). Houve aumento significativo da massa fresca e seca da parte aérea e de raízes, altura, volume de raízes e do número de perfilhos e de folhas das plantas com a inoculação de MAY12 (com e sem adição de N) em relação a T8. Os tratamentos contendo MAY12 + N aumentaram em torno de 920% a massa seca total em relação a T8, equiparando-se ao rendimento T3. A inoculação de MAY12, isoladamente, foi tão eficiente quanto a aplicação da dose cheia de N para o aumento em torno de 115% da altura e de 373% do volume de raízes das plantas em relação a T8. A estirpe MAY12 apresentou bom desempenho no desenvolvimento da cultivar equiparando-se com o IC nas variáveis testadas. Portanto, a inoculação com a estirpe MAY12 mostra-se promissora para a redução parcial de fertilizantes nitrogenados no cultivo de arroz de terras altas.
Assuntos
Azospirillum/crescimento & desenvolvimento , Oryza/crescimento & desenvolvimentoRESUMO
Osmotic variations in the soil can affect bacterial growth diminishing the number of inoculated bacteria. In a scenario of water deficit having tolerant bacteria would be beneficial to achieve a better response of the plant to stress. Thus, selection of more resistant bacteria could be useful to design new inoculants to be used in arid zones. In this sense, a group of Azospirillum isolates deposited in INTA collection was characterized in order to select strains tolerant to osmotic stress. The results obtained demonstrated that Az19 strain has similar in vitro PGPR characteristics to Az39, the most used strain in Argentina for inoculants industries, with the advantage of a better tolerance to osmotic and salt stress. Inoculation of maize plants with this strain resulted in a better response against water deficit compared to Az39 strain, encouraging us to further study the behavior of this strain in greenhouse and field trials in view of developing new inoculants suitable for areas with water deficit.
Assuntos
Adaptação Fisiológica , Azospirillum/fisiologia , Secas , Pressão Osmótica , Zea mays/crescimento & desenvolvimento , Zea mays/microbiologia , Argentina , Azospirillum/genética , Azospirillum/crescimento & desenvolvimento , Azospirillum/isolamento & purificação , Carbono-Carbono Liases/metabolismo , Sobrevivência Celular , Contagem de Colônia Microbiana , Genótipo , Indóis/metabolismo , Fixação de Nitrogênio , Fosfatos/metabolismo , Prolina/análise , Sementes/crescimento & desenvolvimento , Sideróforos/metabolismo , Solo , Trealose/metabolismo , Água/química , Zea mays/fisiologiaRESUMO
A sustainable alternative to improve yield and the nutritive value of forage is the use of plant growth-promoting bacteria (PGPB) that release nutrients, synthesize plant hormones and protect against phytopathogens (among other mechanisms). Azospirillum genus is considered an important PGPB, due to the beneficial effects observed when inoculated in several plants. The aim of this study was to evaluate the diversity of new Azospirillum isolates and select bacteria according to the plant growth promotion ability in three forage species from the Brazilian Pantanal floodplain: Axonopus purpusii, Hymenachne amplexicaulis and Mesosetum chaseae. The identification of bacterial isolates was performed using specific primers for Azospirillum in PCR reactions and partial sequencing of the 16S rRNA and nifH genes. The isolates were evaluated in vitro considering biological nitrogen fixation (BNF) and indole-3-acetic acid (IAA) production. Based on the results of BNF and IAA, selected isolates and two reference strains were tested by inoculation. At 31 days after planting the plant height, shoot dry matter, shoot protein content and root volume were evaluated. All isolates were able to fix nitrogen and produce IAA, with values ranging from 25.86 to 51.26 mg N mL-1 and 107-1038 µmol L-1, respectively. The inoculation of H. amplexicaulis and A. purpusii increased root volume and shoot dry matter. There were positive effects of Azospirillum inoculation on Mesosetum chaseae regarding plant height, shoot dry matter and root volume. Isolates MAY1, MAY3 and MAY12 were considered promising for subsequent inoculation studies in field conditions.
Assuntos
Azospirillum/classificação , Azospirillum/isolamento & purificação , Poaceae/microbiologia , Azospirillum/genética , Azospirillum/crescimento & desenvolvimento , DNA Fúngico/análise , Ácidos Indolacéticos/metabolismo , Fixação de Nitrogênio , Filogenia , Proteínas de Plantas/análise , Raízes de Plantas/metabolismo , Raízes de Plantas/microbiologia , Poaceae/crescimento & desenvolvimento , Análise de Sequência de DNARESUMO
ResumenLa industria petrolera ha generado derrames crónicos de petróleo y su acumulación en Gleysoles en zonas anegadas en el estado de Tabasco, en el sureste de México. El anegamiento es un factor que limita el uso de tecnologías de remediación por el alto costo y los bajos niveles de degradación del petróleo, sin embargo, Leersia hexandra Sw. es un pasto que crece en estas zonas contaminadas con petróleo intemperizado. El objetivo del estudio fue evaluar la densidad de bacterias, producción de biomasa vegetal y fitorremediación de L.hexandra en suelo contaminado con petróleos fresco e intemperizado, bajo condiciones experimentales de anegamiento. Se realizaron dos experimentos (E1 y E2) en un túnel de plástico. El E1 se basó en ocho dosis: 6 000, 10 000, 30 000, 60 000, 90 000, 120 000, 150 000 y 180 000 mg kg-1 base seca (b.s.) de hidrocarburos totales de petróleo fresco (HTPF), y en el E2 se evaluaron cinco dosis: 14 173, 28 400, 50 598, 75 492 y 112 142 mg kg-1 b. s. de hidrocarburos totales de petróleo intemperizado (HTPI), con ocho repeticiones en cada experimento, además se utilizó un testigo con 2 607 mg kg-1 b. s. de HTP de origen biogénico. Las variables evaluadas a los tres y seis meses fueron 1) densidad microbiana de las bacterias fijadoras de nitrógeno de vida libre totales (BFN), del grupo Azospirillum (AZP) y Azotobacter (AZT), por cuenta viable en placa seriada; 2) producción de materia seca total (MS), se cuantificó por el peso seco por gravimetría, y 3) el porcentaje de descontaminación de los hidrocarburos (DSC) por extracción en equipo soxhlet. En suelos con HTPF, la población de BFN, AZP y AZT se estimuló hasta cinco veces más que el tratamiento testigo a los tres y seis meses; sin embargo, concentraciones de 150 000 y 180 000 mg kg-1 b. s. inhibieron entre un 70 y 89 % la densidad bacteriana. A su vez, en suelos con PI, la inhibición se registró hasta en un 90 %, a excepción del tratamiento con 14 173 mg kg-1 b. s., el cual estimuló las BNF y AZT en 2 y 0.10 veces más que testigo, respectivamente. La producción de MS fue continua en los experimentos hasta los seis meses, con valores de 63 y 89 g en PF y PI, respectivamente; sin diferencias significativas con el testigo (p ≤ 0.05). El DSC alcanzó valores del 66 % al 87 % en HTPF como HTPI a los seis meses, respectivamente. Estos resultados demuestran la habilidad del L. hexandra para desarrollar una rizósfera con alta densidad de BFN, producir biomasa vegetal y fitorremediar Gleysoles con petróleo fresco e intemperizado en ambientes tropicales inundados.
Abstract:The oil industry has generated chronic oil spills and their accumulation in wetlands of the state of Tabasco, in Southeastern Mexico. Waterlogging is a factor that limits the use of remediation technologies because of its high cost and low levels of oil degradation. However, Leersia hexandra is a grass that grows in these contaminated areas with weathered oil. The aim of the study was to evaluate the bacteria density, plant biomass production and phytoremediation of L. hexandra in contaminated soil. For this, two experiments in plastic tunnel were performed with fresh (E1) and weathered petroleum (E2) under waterlogging experimental conditions. The E1 was based on eight doses: 6 000, 10 000, 30 000, 60 000, 90 000, 120 000, 150 000 and 180 000 mg.kg-1 dry basis (d. b.) of total petroleum hydrocarbons fresh (TPH-F), and the E2, that evaluated five doses: 14 173, 28 400, 50 598, 75 492 and 112 142 mg. kg-1 d. b. of total petroleum hydrocarbons weathered (TPH-W); a control treatment with 2 607 mg.kg-1 d. b. was used. Each experiment, with eight replicates per treatment, evaluated after three and six months: a) microbial density of total free-living nitrogen-fixing bacteria (NFB) of Azospirillum (AZP) and Azotobacter group (AZT), for viable count in serial plate; b) dry matter production (DMP), quantified gravimetrically as dry weight of L. hexandra; and c) the decontamination percentage of hydrocarbons (PDH) by Soxhlet extraction. In soil with TPH-F, the NFB, AZP y AZT populations were stimulated five times more than the control both at the three and six months; however, concentrations of 150 000 and 180 000 mg.kg-1 d. b. inhibited the bacterial density between 70 and 89 %. Likewise, in soil with TPH-W, the FNB, AZP and AZT inhibitions were 90 %, with the exception of the 14 173 mg.kg-1 d. b. treatment, which stimulated the NFB and AZT in 2 and 0.10 times more than the control, respectively. The DMP was continued at the six months in the experiments, with values of 63 and 89 g in fresh and weathered petroleum, respectively; had no significant differences with the control (p≤0.05). The PDH reached values of 66 to 87 % both TPH-F and TPH-W at six months, respectively. These results demonstrated the ability the L. hexandra rhizosphere to stimulate the high NFB density, vegetal biomass production and phytoremediation of contaminated soils (with fresh and weathered petroleum), in a tropical waterlogging environment. Rev. Biol. Trop. 65 (1): 21-30. Epub 2017 March 01.
Assuntos
Poluentes do Solo/química , Biodegradação Ambiental , Poluição por Petróleo/prevenção & controle , Poaceae/microbiologia , Poaceae/química , Valores de Referência , Solo/química , Microbiologia do Solo , Azotobacter/crescimento & desenvolvimento , Fatores de Tempo , Petróleo/análise , Contagem de Colônia Microbiana , Reprodutibilidade dos Testes , Azospirillum/crescimento & desenvolvimento , Biomassa , Hidrocarbonetos/análise , Hidrocarbonetos/químicaRESUMO
The oil industry has generated chronic oil spills and their accumulation in wetlands of the state of Tabasco, in Southeastern Mexico. Waterlogging is a factor that limits the use of remediation technologies because of its high cost and low levels of oil degradation. However, Leersia hexandra is a grass that grows in these contaminated areas with weathered oil. The aim of the study was to evaluate the bacteria density, plant biomass production and phytoremediation of L. hexandra in contaminated soil. For this, two experiments in plastic tunnel were performed with fresh (E1) and weathered petroleum (E2) under waterlogging experimental conditions. The E1 was based on eight doses: 6 000, 10 000, 30 000, 60 000, 90 000, 120 000, 150 000 and 180 000 mg.kg-1 dry basis (d. b.) of total petroleum hydrocarbons fresh (TPH-F), and the E2, that evaluated five doses: 14 173, 28 400, 50 598, 75 492 and 112 142 mg. kg-1 d. b. of total petroleum hydrocarbons weathered (TPH-W); a control treatment with 2 607 mg.kg-1 d. b. was used. Each experiment, with eight replicates per treatment, evaluated after three and six months: a) microbial density of total free-living nitrogen-fixing bacteria (NFB) of Azospirillum (AZP) and Azotobacter group (AZT), for viable count in serial plate; b) dry matter production (DMP), quantified gravimetrically as dry weight of L. hexandra; and c) the decontamination percentage of hydrocarbons (PDH) by Soxhlet extraction. In soil with TPH-F, the NFB, AZP y AZT populations were stimulated five times more than the control both at the three and six months; however, concentrations of 150 000 and 180 000 mg.kg-1 d. b. inhibited the bacterial density between 70 and 89 %. Likewise, in soil with TPH-W, the FNB, AZP and AZT inhibitions were 90 %, with the exception of the 14 173 mg.kg-1 d. b. treatment, which stimulated the NFB and AZT in 2 and 0.10 times more than the control, respectively. The DMP was continued at the six months in the experiments, with values of 63 and 89 g in fresh and weathered petroleum, respectively; had no significant differences with the control (p≤0.05). The PDH reached values of 66 to 87 % both TPH-F and TPH-W at six months, respectively. These results demonstrated the ability the L. hexandra rhizosphere to stimulate the high NFB density, vegetal biomass production and phytoremediation of contaminated soils (with fresh and weathered petroleum), in a tropical waterlogging environment.
Assuntos
Biodegradação Ambiental , Poluição por Petróleo/prevenção & controle , Poaceae/química , Poaceae/microbiologia , Poluentes do Solo , Azospirillum/crescimento & desenvolvimento , Azotobacter/crescimento & desenvolvimento , Biomassa , Contagem de Colônia Microbiana , Hidrocarbonetos/análise , Hidrocarbonetos/química , Petróleo/análise , Valores de Referência , Reprodutibilidade dos Testes , Solo/química , Microbiologia do Solo , Poluentes do Solo/química , Fatores de TempoRESUMO
This work aimed to evaluate density of associative diazotrophic bacteria populations in soil and grass root samples from heavy metal contaminated sites, and to characterize isolates from these populations, both, phenotypically (Zinc, Cadmium and NaCl tolerance in vitro, and protein profiles) and genotypically (16S rDNA sequencing), as compared to type strains of known diazotrophic species. Densities were evaluated by using NFb, Fam and JNFb media, commonly used for enrichment cultures of diazotrophic bacteria. Bacterial densities found in soil and grass root samples from contaminated sites were similar to those reported for agricultural soils. Azospirillum spp. isolates from contaminated sites and type strains from non-contaminated sites varied substantially in their in vitro tolerance to Zn+2 and Cd+2, being Cd+2 more toxic than Zn+2. Among the most tolerant isolates (UFLA 1S, 1R, S181, S34 and S22), some (1R, S34 and S22) were more tolerant to heavy metals than rhizobia from tropical and temperate soils. The majority of the isolates tolerant to heavy metals were also tolerant to salt stress as indicated by their ability to grow in solid medium supplemented with 30 g L-1 NaCl. Five isolates exhibited high dissimilarity in protein profiles, and the 16S rDNA sequence analysis of two of them revealed new sequences for Azospirillum.
Objetivou-se avaliar a densidade de populações de bactérias diazotróficas associativas em amostras de solos e de raízes de gramíneas oriundas de sítios contaminados com metais pesados, e caracterizar isolados destas populações através da análise fenotípica (tolerância aos metais pesados zinco e cádmio e à NaCl in vitro, perfis protéicos), e genotípica (seqüenciamento de 16S rDNA), comparados às estirpes tipo das mesmas espécies. As densidades foram avaliadas nos meios NFb, Fam e LGI, comumente utilizados para culturas de enriquecimento de populações de bactérias diazotróficas associativas. As densidades encontradas em amostras de solo e raiz de sítios contaminados foram semelhantes àquelas relatadas na literatura para solos agrícolas. Isolados de Azospirillum spp. de solos contaminados e estirpes tipo oriundas de solos não contaminados variaram substancialmente com relação à tolerância a Zn+2 e Cd+2, sendo que Cd+2 mais tóxico que Zn+2. Dentre os isolados mais tolerantes (UFLA 1S, 1R, S181, S34, e S22), alguns(1R, S34 e S22) foram mais tolerantes a metais pesados que rizóbios isolados de solos de áreas tropicais e temperadas. A maioria dos isolados mais tolerantes a metais pesados também foi tolerante ao estresse salino, o que foi indicado por seu crescimento em meio sólido suplementado com 30 g L-1 de NaCl in vitro. Cinco isolados apresentaram alta dissimilaridade em perfis protéicos e o seqüenciamento do gene 16S rDNA em dois deles revelou que apresentam novas seqüências de Azospirillum.
Assuntos
Azospirillum/efeitos dos fármacos , Burkholderia/efeitos dos fármacos , Herbaspirillum/efeitos dos fármacos , Metais Pesados/toxicidade , Raízes de Plantas/microbiologia , Poaceae/microbiologia , Microbiologia do Solo , Azospirillum/genética , Azospirillum/crescimento & desenvolvimento , Burkholderia/genética , Burkholderia/crescimento & desenvolvimento , Contagem de Colônia Microbiana , DNA Bacteriano/genética , Farmacorresistência Bacteriana/genética , Genótipo , Herbaspirillum/genética , Herbaspirillum/crescimento & desenvolvimento , Metais Pesados/análise , Fenótipo , /genéticaRESUMO
This work aimed to evaluate density of associative diazotrophic bacteria populations in soil and grass root samples from heavy metal contaminated sites, and to characterize isolates from these populations, both, phenotypically (Zinc, Cadmium and NaCl tolerance in vitro, and protein profiles) and genotypically (16S rDNA sequencing), as compared to type strains of known diazotrophic species. Densities were evaluated by using NFb, Fam and JNFb media, commonly used for enrichment cultures of diazotrophic bacteria. Bacterial densities found in soil and grass root samples from contaminated sites were similar to those reported for agricultural soils. Azospirillum spp. isolates from contaminated sites and type strains from non-contaminated sites varied substantially in their in vitro tolerance to Zn+2 and Cd+2, being Cd+2 more toxic than Zn+2. Among the most tolerant isolates (UFLA 1S, 1R, S181, S34 and S22), some (1R, S34 and S22) were more tolerant to heavy metals than rhizobia from tropical and temperate soils. The majority of the isolates tolerant to heavy metals were also tolerant to salt stress as indicated by their ability to grow in solid medium supplemented with 30 g L(-1) NaCl. Five isolates exhibited high dissimilarity in protein profiles, and the 16S rDNA sequence analysis of two of them revealed new sequences for Azospirillum.
Assuntos
Azospirillum/efeitos dos fármacos , Burkholderia/efeitos dos fármacos , Herbaspirillum/efeitos dos fármacos , Metais Pesados/toxicidade , Raízes de Plantas/microbiologia , Poaceae/microbiologia , Microbiologia do Solo , Azospirillum/genética , Azospirillum/crescimento & desenvolvimento , Burkholderia/genética , Burkholderia/crescimento & desenvolvimento , Contagem de Colônia Microbiana , DNA Bacteriano/genética , Farmacorresistência Bacteriana/genética , Genótipo , Herbaspirillum/genética , Herbaspirillum/crescimento & desenvolvimento , Metais Pesados/análise , Fenótipo , RNA Ribossômico 16S/genéticaRESUMO
Azospirillum-plant association is accompanied by biochemical changes in roots which, in turn, promote plant-growth and tolerance to water stress. To shed light on the possible factors underlying these effects, roots from Azospirillum brasilense Sp245-inoculated Triticum aestivum seedlings growing in darkness under osmotic stress were analyzed for phospholipid (PL) composition, fatty acid (FA) distribution profiles and degree of unsaturation of the major PL classes. Azospirillum inoculation diminished ion leakage and increased 2,3,5-tripheniltetrazolium reducing ability in roots of well irrigated and water-stressed wheat seedlings. Total root PL content remained unaltered in all treatments. Six PL classes were detected, phosphatidylcholine (PC) and phosphatidylethanolamine (PE) comprising over 80% of the total. While water stress increased PC content and diminished that of PE, none of these changes were observed either under Azospirillum inoculation alone or when both treatments were combined. The major FAs found in both PC and PE were 16:0, 18:0, 18:1, 18:2, and 18:3. Higher PC and lower PE unsaturation than in well irrigated controls were observed in roots from Azospirillum-inoculated, water-stressed seedlings. Azospirillum inoculation could contribute to protect wheat seedlings from water stress through changes in the FA distribution profiles of PC and PE major root phospholipids.
Assuntos
Azospirillum , Fosfolipídeos/biossíntese , Raízes de Plantas/metabolismo , Plântula/metabolismo , Triticum/metabolismo , Azospirillum/crescimento & desenvolvimento , Azospirillum/metabolismo , Desidratação/metabolismo , Raízes de Plantas/microbiologia , Plântula/microbiologia , Triticum/microbiologiaRESUMO
In vitro gluconic acid formation and phosphate solubilization from sparingly soluble phosphorus sources by two strains of the plant growth-promoting bacteria A. brasilense (Cd and 8-I) and one strain of A. lipoferum JA4 were studied. Strains of A. brasilense were capable of producing gluconic acid when grown in sparingly soluble calcium phosphate medium when their usual fructose carbon source is amended with glucose. At the same time, there is a reduction in pH of the medium and release of soluble phosphate. To a greater extent, gluconic acid production and pH reduction were observed for A. lipoferum JA4. For the three strains, clearing halos were detected on solid medium plates with calcium phosphate. This is the first report of in vitro gluconic acid production and direct phosphate solubilization by A. brasilense and the first report of P solubilization by A. lipoferum. This adds to the very broad spectrum of plant growth-promoting abilities of this genus.
Assuntos
Azospirillum/metabolismo , Gluconatos/metabolismo , Fosfatos/metabolismo , Saccharum/crescimento & desenvolvimento , Saccharum/microbiologia , Azospirillum/crescimento & desenvolvimento , Azospirillum brasilense/crescimento & desenvolvimento , Azospirillum brasilense/metabolismo , Cuba , CinéticaRESUMO
Azospirillum spp. are endophytic bacteria with beneficial effects on cereals--effects partially attributed to gibberellin production by the microorganisms. Azospirillum lipoferum and Azospirillum brasilense inoculated to rice dy mutant reversed dwarfism in seedlings incubated with [17,17-2H2]GA20 with formation of [17,17-2H2]GA1, showing the in vivo capacity to perform the 3beta-hydroxylation. When prohexadione-Ca, an inhibitor of late steps in gibberellin biosynthesis, was added to the culture medium, no complementation was observed and no [17,17-2H2]GA1 was produced. The latter suggests that the bacterial operating enzyme may be a 2-oxoglutarate-dependent dioxygenase, similar to those of plants.
Assuntos
Azospirillum brasilense/metabolismo , Azospirillum/metabolismo , Giberelinas/metabolismo , Oryza/microbiologia , Azospirillum/crescimento & desenvolvimento , Azospirillum brasilense/crescimento & desenvolvimento , Deutério , Cromatografia Gasosa-Espectrometria de Massas , Giberelinas/química , Hidrólise , Mutagênese , Oryza/genética , Oryza/crescimento & desenvolvimento , Oryza/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Raízes de Plantas/microbiologia , Microbiologia do SoloRESUMO
Azospirillum species are plant growth-promotive bacteria whose beneficial effects have been postulated to be partially due to production of phytohormones, including gibberellins (GAs). In this work, Azospirillum brasilense strain Cd and Azospirillum lipoferum strain USA 5b promoted sheath elongation growth of two single gene GA-deficient dwarf rice (Oryza sativa) mutants, dy and dx, when the inoculated seedlings were supplied with [17,17-2H2]GA20-glucosyl ester or [17,17- 2H2]GA20-glucosyl ether. Results of capillary gas chromatography-mass spectrometry analysis show that this growth was due primarily to release of the aglycone [17,17-2H2]GA20 and its subsequent 3beta-hydroxylation to [17,17-2H2]GA1 by the microorganism for the dy mutant, and by both the rice plant and microorganism for the dx mutant.
Assuntos
Azospirillum brasilense/metabolismo , Azospirillum/metabolismo , Giberelinas/metabolismo , Oryza/microbiologia , Oryza/fisiologia , Azospirillum/crescimento & desenvolvimento , Azospirillum brasilense/crescimento & desenvolvimento , Deutério , Cromatografia Gasosa-Espectrometria de Massas , Genes de Plantas , Giberelinas/química , Hidrólise , Oryza/genética , Raízes de Plantas/metabolismoRESUMO
An experiment was carried out in order to evaluate the effect of pH on Azospirillum sp. growth and survival in maize rhizosphere. Sterilized maize seeds were sown in a perlite substratum with addition of a nutritive medium. The pots were buffered at two different pHs: 5.8 (group one) and 7.0 (group two). Each group was divided in two treatments: inoculated with Azospirillum sp. Az-39 and non-inoculated. Experimental pots were incubated at 20 degrees C with a 14 hour photoperiod. Growth of non-inoculated roots was negligible. Inoculated roots showed a better response at pH 5.8 than at 7.0. Several accompanying bacteria were found. Azospirillum grew in both groups with a low penetration into roots. A set of nutritive relationships among microorganisms and maize roots was observed; Xanthomonas is a maize pathogenic bacteria, and it is a NO3- consumer, and uses this anion as hydrogen acceptor. The Gram (-) Diplococcus is a nitrate producer . Cytophaga and Flavobacterium are related with roots decomposition. It is concluded that Azospirillum improves the root growth, mainly at pH 5.8.