Effects of different forms of nitrogen on rhizosphere microbial community structure of Eichhornia crassipes (Pontederiaceae)

AbstractRhizosphere microbial communities are important for phytoremediation, plant nutrition, health and metabolism. Many factors, including plant species, pH and nutritional factors influence rhizosphere microbiology. In this study, we analysed the effects of different forms of nitrogen on the structures of rhizosphere microbial communities of E. crassipes. Using a conventional culture method with special media, bacteria, actinobacteria and molds were cultured. We found that the numbers of bacteria were largely similar across the three culture conditions, while the numbers of actinobacteria and molds from the rhizosphere of E. crassipes cultured in NH4Cl solution were two orders of magnitude higher than those from the rhizospheres of plants cultured in distilled water and KNO3 solution. Using a culture-independent method of polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) of 16S rDNA, we found that the form of nitrogen could influence the components of the rhizosphere microbial community. Pseudoxanthomonas, Enterobacter and Citrobacter were present in all of the samples cultured under the three different experimental conditions. The genus Reyranella was found only in samples cultured in KNO3 solution; Acinetobacter and Streptomyces were unique to samples cultured in NH4Cl solution, and Pseudomonas, Pseudacidovorax and Methylosinus were found only in samples cultured in distilled water. Pseudoxanthomonas and Acidovorax were the dominant genera in the rhizosphere microbial community of E. crassipes cultured in KNO3 solution, while Novosphingobium was the dominant genus in the sample cultured in a nitrogen-deficient medium. Our results provide a theoretical foundation for using E. crassipes as a phytoremediation plant and controlling the widespread distribution of E. crassipes around the world using principles of nutrient metabolism.

ResumenComunidades microbianas de la rizósfera son importantes para la fitorremediación, nutrición vegetal, salud y metabolismo. Muchos factores, incluyendo la especie de planta, el pH y los factores nutricionales influyen en la microbiología de la rizósfera. En este estudio, se analizaron los efectos de las diferentes formas del nitrógeno en la estructura de las comunidades microbianas de la rizósfera de E. crassipes. Mediante métodos de cultivo convencional con medios especiales se cultivaron: bacterias, actinobacterias y mohos. Se encontró que el número de bacterias era en gran parte similar a través de las tres condiciones de cultivo, mientras que el número de actinobacterias y mohos de la rizósfera de E. crassipes cultivadas en solución de NH4Cl era dos órdenes de magnitud superior a los de las rizósferas de plantas cultivadas en agua destilada y solución de KNO3. Utilizando un método de cultivo independiente de electroforesis en gel con gradiente de desnaturalización (PCR-DGGE) del ADNr 16S, se encontró que la forma de nitrógeno podría influir en los componentes de la comunidad microbiana de la rizósfera. Pseudoxanthomonas, Enterobacter y Citrobacter estaban presentes en todas las muestras cultivadas en las tres condiciones experimentales. El género Reyranella se encontró sólo en muestras cultivadas en solución de KNO3; Acinetobacter y Streptomyces eran las únicas muestras cultivadas en solución de NH4Cl, y Pseudomonas, Pseudacidovorax y Methylosinus se encontraron sólo en muestras cultivadas en agua destilada. Pseudoxanthomonas y Acidovorax eran los géneros dominantes en la comunidad microbiana de la rizósfera de E. crassipes cultivadas en solución de KNO3, mientras que Novos phingobium fue el género dominante en la muestra cultivada en un medio deficiente de nitrógeno. Nuestros resultados proporcionan una base teórica para el uso de E. crassipes como planta fitorremediadora y para controlar la distribución generalizada de E. crassipes en todo el mundo a través de los principios del metabolismo de nutrientes.

Changes in morphology of long bone marrow tissue of rats submitted to cryotherapy with liquid nitrogen / Alterações na morfologia do tecido medular de ossos longos de ratos submetido à crioterapia com nitrogênio líquido

PURPOSE: To study the main effects of local use of liquid nitrogen on bone marrow tissue in rats. METHODS: The femoral diaphyses of 42 Wistar rats were exposed to three local and sequential applications of liquid nitrogen for one or two minutes, intercalated with periods of five minutes of passive thawing. The animals were sacrificed after one, two, four and 12 weeks and the specimens obtained were analyzed histomorphologically. RESULTS: In the second experimental week of one-minute protocol, histological degree of inflammation obtained a mean score of one (mild), ranging from 0 (absent or scarce) and two (moderate) (Kruskal-Wallis test p=0.01). In the second experimental week of two-minute protocol, degree of inflammation to the medullar tissue obtained an average score of two (Kruskal-Wallis test p=0.01). CONCLUSION: The degree of inflammation of the bone marrow tissue was higher in protocol of three applications of two minutes compared to protocol of three applications of one minute.

OBJETIVO: Investigar os principais efeitos do uso local de nitrogênio líquido sobre o tecido medular ósseo em ratos. MÉTODOS: As diáfises femorais de 42 ratos Wistar foram expostas a três aplicações sequenciais locais de nitrogênio líquido por um ou dois minutos, intercaladas por períodos de cinco minutos de degelo espontâneo. Os animais foram sacrificados após uma, duas, quatro e 12 semanas e os espécimes obtidos foram analisados histomorfologicamente. RESULTADOS: Na segunda semana experimental do protocolo de um minuto, o grau histológico de inflamação obteve um escore médio de um (leve) variando entre 0 (ausente ou escarço) a dois (moderado) (Teste de Kruskal-Wallis p=0.01). Na segunda semana experimental do protocolo de dois minutos, o grau histológico de inflamação do tecido medular obteve um escore máximo de dois (moderado) (Teste de Kruskal-Wallis p=0.01). CONCLUSÃO: O grau de inflamação do tecido medular ósseo foi maior no protocolo de três aplicações de dois minutos comparado ao protocolo de três aplicações de um minuto.

Relación de la fijación de nitrógeno y la producción de auxinas en cepas de Gluconacetobacter dizotrophicus / Relationships between nitrogen fixation and auxins production in Gluconacetobacter diazotrophicus strains from different crops

Se determinó la capacidad de fijar nitrógeno mediante la actividad reductora de acetileno para 8 cepas de G. diazotrophicus aisladas de diferentes ecosistemas empleando el medio LGI-P. Además, se determinó la producción de auxinas a través del método de Salkowski y se analizó la influencia del aminoácido triptófano y del AIA en la actividad de la nitrogenasa. El triptófano, al igual que otros aminoácidos y las diferentes concentraciones de AIA, inhiben en distinta medida la actividad de la enzima solo parcialmente. Se demostró que las condiciones de nitrofijación no afectan la producción de AIA en esta bacteria. Esta relación entre ambas capacidades fisiológicas beneficiosas para los cultivos agrícolas pudiera tener gran importancia ya que pueden desarrollarse paralelamente, y potenciar la acción beneficiosa hacia la planta, basada en la dinitrofijación y la producción de auxinas estimuladoras del crecimiento vegetal.

The capacity to fix nitrogen of 8 strains of G. diazotrophicus from different ecosystems was determined by acetylene reduction assay using LGIP medium. Moreover, auxins production was determined by Salkowski’s method and the influence of triptophan and indoleacetic acid (IAA) in the nitrogenase activity were analyzed. The triptophan as other aminoacids and different concentrations of IAA, inhibit at different levels the nitrogen fixation only partially. There were demonstrated that the nitrogen fixation conditions do not affect the auxins production of this bacteria. This relationship between both crop beneficial physiological capacities should be a great importance since they may be parallely developed, and enhance the beneficial action to the plant, based on dinitrogen fixation and stimulating plant growth auxins production.

Metabolismos microbianos involucrados en procesos avanzados para la remoción de nitrógeno, una revisión prospectiva / Microbial metabolisms over advanced processes for nitrogen removal, a prospective review

Los procesos avanzados para la remoción de nitrógeno están íntimamente relacionados con los metabolismos de las comunidades microbianas que intervienen en las transformaciones del mismo. Para el diseño, la optimización o el mejoramiento de los sistemas de tratamiento de aguas residuales domésticas, el ingeniero y el microbiólogo en forma conjunta, han logrado configurar reactores terciarios adecuados para el desenvolvimiento de estas comunidades, obteniendo altas eficiencias de remoción de los nutrientes. Este artículo presenta una revisión sobre la actividad bacteriana y su aplicación en los sistemas de tratamiento, inicia conceptualizando la influencia de los microorganismos y de la actividad humana en el ciclo global del nitrógeno, para después hacer un análisis de los procesos particulares en los cuales los microorganismos intervienen. Se clasifican e incluyen nuevas evidencias de metabolismos relacionados, y se describen como ejemplos algunos de los procesos de tratamiento terciario para aguas residuales desarrollados con éxito en las últimas décadas.

Advanced processes for nitrogen removal are intimately related to the microbial community metabolisms that take part in the transformations. For the design, optimization or improvement of domestic waste water treatment systems, engineers and microbiologists working together, have managed to implemented suitable tertiary reactors for the development of these communities, improving the efficiency of nutrient removal. This article presents a revision of the bacterial activity and its application in treatment systems. The article begins by giving an explanation about the influence of microorganism and human activity on the global nitrogen cycle. Then, it analyzes the particular processes in which the microorganisms take part. New evidence of related metabolisms are classified and included. Some of the processes of wastewater tertiary treatment, successfully developed over the last decades, are described as examples.

The effect of nitrogen and potassium fertilizers on growth parameters and carbohydrate contents of sweet sorghum cultivars.

Sweet sorghum is tolerant to high temperature and drought and can be considered as an alternative crop to sugar beet and maize in Iran. In this study, the effects of nitrogen and potassium fertilizers on growth parameters including stem height, stem diameter, stem fresh weight, total fresh weight; carbohydrate contents including total sugar, brix value, sucrose content and purify; and juice extract of two sweet sorghum cultivars were determined. Three rates of N-fertilizer (0, 90, 180 kg urea ha(-1)) and two rates of K fertilizer (0 and 50 kg potassium sulfate ha(-1)) assigned as main plots and two sweet sorghum cultivars (Rio and Keller) as subplots. Growth parameters at soft dough and physiological maturity stages and carbohydrate contents at physiological maturity stage were determined. Results showed that application of 180 kg urea ha(-1) as compared to control at physiological maturity significantly (p < 0.01) increased stem height (12.65%), stem fresh weight (24.57%), total fresh weight (78.22%), total sugar (39.25%), sucrose content (9%) and juice extract (34.96%). Application of 50 kg potassium sulfate ha(-1) increased (p < 0.05) stem fresh weight (24.33%), total fresh weight (25.44%), total sugar (10.50%), and juice extract (9%) at physiological maturity. The highest growth parameters, carbohydrate contents and juice extract were obtained with the application of 180 kg urea ha(-1) and 50 kg potassium sulfate ha(-1) using cultivar (cv) Keller. The best results were taken with the application of both fertilizers.

Efeitos da adubação nitrogenada em algodoeiro sobre a biologia de Aphis gossypii Glover (Hemiptera: Aphididae) / Effects of nitrogen fertilization in cotton crop on Aphis gossypii Glover (Hemiptera: Aphididae) biology

O pulgão Aphis gossypii Glover é uma das pragas do algodoeiro e suas relações com o hospedeiro são dependentes da quantidade de nitrogênio disponível para a planta. A biologia do A. gossypii, em função do regime de adubação nitrogenada no algodoeiro, foi estudada em condições de casa-de-vegetação, em Dourados, MS. Para isto foi utilizado o delineamento experimental inteiramente casualizado com nove repetições, com os tratamentos arranjados em fatorial (2 x 4 x 2) + 1, com duas fontes de adubo nitrogenado, quatro doses de nitrogênio (50, 100, 150 e 200 kg ha-1), duas épocas de aplicação do nitrogênio em cobertura e um tratamento adicional sem a adição do nitrogênio. Foram avaliadas as durações dos estádios ninfais e da fase ninfal, os períodos pré-reprodutivo, reprodutivo e pós-reprodutivo, a longevidade, o ciclo biológico e a fecundidade dos pulgões. Concluiu-se que apenas as doses de nitrogênio influenciaram a biologia do pulgão-do-algodoeiro, independente da fonte e época de aplicação, favorecendo seu desenvolvimento e fecundidade.

The cotton aphid, Aphis gossypii Glove, is one of the pests of cotton crop and its relation with the host seem to depend on the amount of nitrogen available to the plant. The biology of A. gossypii using different cotton nitrogen fertility regimes was studied under greenhouse conditions, in Dourados, MS. A completely randomized design with nine replications in a factorial scheme (2x4x2)+1 was used. Two nitrogen sources (sulphate of ammonium and urea), four doses of nitrogen (50, 100, 150 and 200 kg ha-1), two different times of nitrogen application and one additional treatment without nitrogen were taken as factors. The nymphal phases, the pre-reproductive, reproductive and pos-reproductive periods, longevity, the life cycle and fecundity of the cotton aphid were evaluated. The doses of nitrogen influenced the cotton aphid biology in both sources and times of application, favoring its development and fecundity.

Iron mediated regulation of growth and siderophore production in a diazotrophic cyanobacterium Anabaena cylindrica.

Iron mediated regulation of growth and siderophore production has been studied in a diazotrophic cyanobacterium Anabaena cylindrica. Iron-starved cells of A. cylindrica exhibited reduced growth (30%) when the cells were growing under N2-fixing conditions. In contrast, N03-, NO2-, NH4' and urea grown cells exhibited almost 50% reduction in their growth in the absence of iron as compared to their respective counterparts cultured in the presence of iron. However, at 60 microM of iron, A. cylindrica cells exhibited almost equal growth regardless of the nitrogen source available. Siderophore production in A. cylindrica was started after day 2nd of the cell growth and attained its optimal level on day 5th when the cells were at their mid-log phase. No siderophore production was, however, recorded on day 2nd at all the concentrations of iron tested. The production of siderophore in A. cylindrica further increased with increase in iron concentration and attained its optimum level on day 5th at 60 microM iron. A. cylindrica cells took at least 3 days for initiation of siderophore production and produced about 60% siderophore on day 5th even under iron-starved condition. A. cylindrica produced dihydroxamate type of siderophore.

Effect of nitrogen on Passiflora suberosa L. (Passifloraceae) and consequences for larval performance and oviposition in Heliconius erato phyllis (Fabricius) (Lepidoptera: Nymphalidae)

Avaliou-se a influência do nitrogênio no crescimento e nas características morfológicas e nutricionais de Passiflora suberosa L. e as conseqüências no desempenho larval e oviposição de Heliconius erato phyllis (Fabricius). Foram utilizados três níveis de nitrogênio no solo (tratamentos) para o cultivo de P. suberosa: 0, 150 e 300 mg L-1. Larvas recém-eclodidas foram criadas em laboratório (25 ± 1ºC), individualmente, em ramos das plantas cultivadas em cada tratamento e fêmeas capturadas em campo foram submetidas a testes de escolha para oviposição. A taxa de crescimento, a área foliar e o comprimento dos internódios de P. suberosa aumentaram significativamente com a adição de nitrogênio. A dureza das folhas jovens nas plantas cultivadas sem adição de nitrogênio foi maior, as quais também apresentaram menor conteúdo de água. Houve maior concentração de nitrogênio e potássio nas plantas cultivadas com a adição de nitrogênio no solo. A qualidade nutricional do alimento expressa pela maior concentração de nitrogênio e água, diminuiu o tempo de desenvolvimento larval e aumentou o tamanho dos adultos, embora não tenha afetado a sobrevivência de forma significativa. As fêmeas escolheram os ramos das plantas fertilizadas para oviposição, o que foi positivamente relacionado com desempenho das larvas. Isto poderia explicar a manutenção desse comportamento, bem como a escolha por ramos maiores, registrado em estudos anteriores.

Seed germination in response to chemicals: effect of nitrogen and pH in the media.

Seed germination generally presents a peak in the next growing season after a fire. Among other factors associated with fire are the increase of soil nitrogen and changes in the pH of the soil. In this study, we addressed the question, whether or not the germination response of eight species is linked with the increase in pH and nitrogenous compounds in the germination media? We assessed the separate and combined effects of nitrogenous compounds and pH on the percentage and rate of germination of seeds of Medicago arabica (L.) Hudson, Epilobium hirsutum L., Foeniculum vulgare Miller, Daucus carota L., Thapsia villosa L., Cynosurus cristatus L., Dactylis glomerata L. and Rumex crispus L. All these species are well represented in the Mediterranean ecosystems of the central-west Spain. Water and CaCl2 were used as controls. Nitrogenous compounds increased percent germination (level) and rate in three of the species studied. High pH negatively affected the germination rate of seeds from most species, but had no effect on the per cent germination of any of the species. The higher concentration of the nutritious solutions affected negatively the germination level and rate. The different germination responses of seeds of the studied species could not be exclusively attributed to pH values in the media, whereas the amount and form of Nitrogen in the media has a greater effect on it. These differences in germination are species dependent.

Differences in the levels of aminoacylation and contents of modified nucleotides between total tRNAs from N2- and NH4(+)-grown Azospirillum lipoferum cells.

Total tRNAs isolated from N2- and NH4(+)-grown Azospirillum lipoferum cells were compared with respect to amino acid acceptance, isoacceptor tRNA species levels and extent of nucleotide modifications. Amino-acylation of these two tRNA preparations with ten different amino acids indicated differences in the relative acceptor activities. Comparison of aminoacyl-tRNA patterns by RPC-5 column chromatography revealed no qualitative differences in the elution profiles. However, quantitative differences in the relative amounts of some isoacceptors were observed. These results indicate that alterations of relative amounts of functional tRNA species occur to match cellular requirements of the bacterial cells using N2 or NH4+ as nitrogen source. In addition, the content of modified nucleotides in total tRNAs of N2- and NH4(+)-grown cells was determined. In the NH4(+)-grown cells, content of most of the modified nucleotides decreased significantly. Based upon these results, the relationship of chargeability of tRNAs to base modifications is discussed.

Liquid nitrogen cryopreservation of Bracoccidioides brasiliensis in Fava's Netto medium

Foi demonstrada a viabilidade do uso do meio de Fava Netto na técnica de criopreservaçäo de células de Pb em nitrogênio líquido

La colección de líneas celulares del Laboratorio Conmemorativo Gorgas / The collection of cell lines of the gargas Memorial Laboratory

Se describe la colección de líneas celulares del Laboratorio Conmemorativo Gorgas (LCG). Iniciada hace 22 años, la colección consta de más de 40 líneas celulares, originadas de 15 especies diferentes y preservadas en nitrógeno líquido