Efeito da matéria orgânica e de um inibidor da nitrificação na absorção de 15NH4 e 15NO3 pelo milho

The present experiment, carried out in greenhouse, had the aim to verify the effect of the forms 15NH4 and 15NO3 in presence or absence of organic matter and of the nitrification inhibitor "AM" (2-amino-4-chloro-6-methyil-pyrimidme) in dry matter weight and nitrogen content of the plant derived from soil and from fertilizer. The test plant was the hibrid maize Centralmex. The fertilizers (15NH4)2SO4 and Na15NO3, were added in two levels: 40 and 120 kg N/ha, with 1,02% of 15N and 1,4% of 15N in excess, respectively. Three soils of different physical and chemical characteristics were used: Regossol «intergrade", Latossol Roxo and Podzolizado de Lins e Marília var. Marília. The results showed a better effect of the nitrate form, mainly in the presence of the organic matter, on the absorption of nitrogen by the plants. The presence of organic matter contributed to increase the use of the nitrogen fertilizer in the soils Regossol and Podzolizado, but did not show any significative effect in the Latossol Roxo. The nitrification inhibitor "AM" was neither effective on dry matter weight nor increased the efficiency of the fertilizer. There are also evidences that the presence of the organic matter increased the "A" Value of Latossol Roxo and Podzolizado, but this did not happen in the Regossol, because in this soil, the use of nitrate form alone was better than the treatments with organic mater and "AM". The high "A" Values obtained in the experiment can be attributed, in part, to the short period of the experiment, The "A" Value may not express the real nutritive potential of the soil nitrogen.O presente experimento, conduzido em casa de vegetação, teve como objetivo verificar o efeito das formas 15NH4 e 15NO3 em presença ou ausência de matéria orgânica e de um inibidor da nitrificação "AM" (2-amino-4-cloro-6-metil-pirimidina) na produção de massa e no teor de nitrogênio na planta proveniente do solo e do fertilizante. A planta indicadora, foi o milho híbrido Centralmex. Os adubos (15NH4)2SO4 e Na15NO3, foram adicionados em dois níveis: 40 e 120 kg N/ha, sendo o primeiro com 1,02% de 15N em excesso e o segundo com 1,48% de 15N em excesso. Três solos de características físicas e químicas diferentes foram usados: Regossol "intergrade", Latossol Roxo e Podzolizado de Lins e Marília var. Marília. Pelos resultados obtidos, a forma nítrica apresentou melhor efeito na absorção de nitrogênio do que a forma amoniacal, quando ambas as formas estavam em presença da matéria orgânica. A presença da matéria orgânica contribui para aumentar o aproveitamento do fertilizante nos solos Regossol e Podzolizado, não apresentando porém efeito significativo no Latossol Roxo. O inibidor da nitrificação "AM" não foi efetivo nem para a produção de matéria seca, nem aumentou a eficiência do fertilizante. Há evidências também de que a presença da matéria orgânica contribui para um aumento no Valor "A" do Latossol Roxo e Podzolizado, não acontecendo porém para o Regossol, pois o uso apenas do nitrato superou os tratamentos com matéria orgânica e "AM". A forma amoniacal do fertilizante foi superior à nítrica somente no Latossol Roxo, no aumento da disponibilidade do nitrogênio existente no solo. Os altos Valores "A" obtidos no experimento podem ser atribuídos, em parte, ao curto período do experimento. Ele pode pois, não exprimir o potencial nutritivo real do nitrogênio do solo

A vantagem dos mutantes resistentes à estreptomicina na competição e sobrevivência de Rhizobium Phaseoli em turfa comercial

Survival and competitive abilities of spontaneous mutants of R. phaseoli resistant to antibiotics were studied by means of inoculation in commercial nonsterile and irradiated peat (5 Mrad of gamma radiation). There was a high number of microorganisms (actinomycetes and protozoa) antagonistic to Rhizobium in nonsterile peat and irradiation contributed to a better growth and_ survival of Rhizobium, which after 180 days remained with a number of agriculturally viable cells above 10 8 .The death rates during storage at 5°C of the streptomycin resistant mutants were smaller than those of spectinomycin resistant mutants, specially in the nonsterile peat. Other experiments carried out with nonsterile peat confirmed a better survival of the mutants' to streptomycin in comparison to those resistant to spectinomycin and novobiocin, even when inoculated both together and at rates ten times lower. The results demonstrate the advantageous use of mutants in studies involving the action of biotic and abiotic factors on Rhizobium survival in nonsterile peat.Avaliou-se a sobrevivência e a capacidade de competição de mutantes espontâneos de Rhizobium phaseoli resistentes à estreptomicina e espectinomicina em turfa comercial não esterilizada e esterilizada por irradiação (5 Mrad de radiação gama). Encontrou-se um elevado número de microrganismos antagônicos (actinomicetos e protozoários) na turfa não-esterilizada, e a irradiação favoreceu o crescimento e a longevidade do Rhizobium, que após 180 dias, permaneceu com um número de células viáveis para utilização agrícola (acima de 108). As taxas de mortalidade na turfa armazenada a 5°C foram, em geral, menores nos mutantes resistentes à estreptomicina que nos resistentes à espectinomicina, principalmente na turfa não- irradiada. Outros experimentos conduzidos com turfa não-esterilizada confirmaram a superioridade dos mutantes resistentes à estreptomicina em comparação aos resistentes à espectinomicina e novobiocina, mesmo quando inoculados juntos e em concentrações dez vezes menores. Os resultados obtidos atestam a possibilidade de utilização de mutantes com uma técnica rápida e precisa em estudos envolvendo a ação de fatores biológicos e não-biológicos sobre a população de Rhizobium em turfa não-esterilizada

The nitrogen relationships of maize/bean associations

Intercropping of maize and beans is practiced widely throughout the tropical and subtropical regions of Latin America, particularly among small farmers with limited technical resources. This paper reviews how association affects the nitrogen (N) balance of legumes and nonlegumes, paying particular attention to N2 fixation and N transfer

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Foram estudados os três parâmetros - fixação de 15N2, redução de C2H2 e evolução de H2 para medida da fixação de N2 em nódulos de plantas de feijoeiro (Phaseolus vulgaris L.) de diferentes idades, desenvolvidas em condições controladas de luz e temperatura. A redução de C2H2, cuja metodologia foi caracterizada em laboratório, foi positivamente correlacionada com o N fixado. Demonstrou-se que a técnica necessita de padronização rigorosa na amostragem e que deve ser criteriosa para minimizar os erros experimentais. Cuidados com a incubação dos nódulos (tempo, temperatura adequados) e armazenamento das amostras para cromatografia, podem diminuir muito as variações entre as repetições. Não foi encontrada diferença significativa na redução de C2H2 pelos sistemas estudados - raízes noduladas, plantas inteiras perturbadas ou plantas intactas, na primeira hora de medida. A medida da evolução de H2 foi detectada em nódulos com mais de 20 dias de idade, foi positivamente correlacionada com fixação de N2 e redução de C2H2, sendo decisiva para manter o equilíbrio no balanço eletrônico entre os três parâmetros estudados. A máxima evolução de H2 ocorreu entre 20-30 dias apôs plantio, nas condições de fitotron. Dois métodos foram aplicados para obtenção das razões C2H2: N2 e C2H4/(3N2 + H2). No primeiro, valores entre 3,0 a 11,4 foram obtidos, incubando-se plantas inteiras perturbadas. O balanço eletrônico C2H4/(3N2 + H2) entre os dados variou de 1,57 a 1,75. No segundo método, usando raízes noduladas de diferentes plantas para determinação do N fixado e redução de C2H2, as médias das razões C2H2:N2 estiveram entre 7,4 a 8,3 para todas as idades. O balanço eletrônico in vivo C2H4/( 3N2 + H2) proporcionou valores superiores a 1, de 1,32 a 1,43. Estes dados sugerem que pode estar havendo uma superestimativa da fixação real de N2 pelo método da redução de C2H2. Neste caso, precauções devem ser tomadas ao se utilizar a técnica da redução de C2H2 para estimativa da fixação de N2 em feijoeiro, uma vez que ela pode superestimar em média 32-43% do seu valor real. Nódulos com idade entre 20 a 30 dias proporcionaram medidas dos três parâmetros (fixação de 15N2, redução de C2H2 e evolução de H2) com menores variações.To measure N2 -fixation in nodules of beans (Phaseolus vulgaris L.), of different ages and kept under controlled light and temperature conditions, three parameters 15N2- fixation, C2H2 reduction and H2 evolution - have been studied. C2H2 reduction, the method for which was characterized in the laboratory, was definitely related to the N2-fixed. It was demonstrated that a standardization for sampling is necessary and criterium should be established to keep experimental errors to a minimum. ln order to greatly decrease the variation between replications, the nodules should be carefully incubated (adequate time and temperature), and also the samples should be carefully stored for chromatography. No significant difference was found in C2H2 reduction in the systems studied - nodulated roots, disturbed whole plants and intact plants - in the first hour of measurement. H2 evolution was detected in nodules over 20 days of age and was definitely related to N2-fixation and C2H2 reduction. It was noted that it is absolutely essential to maintain the equilibrium between the three parameters in the electron balance ratio. Maximum H2 evolution occurred 20 - 30 days after planting, under phytotron conditions. Two methods were used to obtain the ratios C2H2:N2 and C2H4/(3N2 + H2). Values from 3.0 to 11.4 were obtained using the first method - incubation of disturbed whole plants. The electron balance values were over 1, varying from 1.32 to 1.43. These data suggest that overestimation of actual N2 -fixation using the C2H2 reduction technique might be occurring. ln this case, this method should be used with great care to avoid an overestimation of on average 32 - 43% of the actual value. Variation was smaller between the measures of the three parameters when 20 - 30 days old nodules were used

Real-time Polymerase Chain Reaction Quantification of Porphyromonas gingivalis and Tannerella forsythia in Primary Endodontic Infections

Introduction: Porphyromonas gingivalis and Tannerella forsythia are anaerobic bacteria commonly involved in root canal infections. Although previous investigations have assessed these species by strictly qualitative approaches, accurate determination of their cell levels by a sensitive quantitative technique may contribute with additional information regarding relevance in pain of endodontic origin. Method: The root canal levels of P gingivalis, T forsythia, and total bacteria were investigated by a quantitative polymerase chain reaction (PCR) assay based on unique copy molecular markers. A total of 32 symptomatic (n = 14) and asymptomatic (n = 18) cases of endodontic infections were analyzed. Root canal samples were collected; genomic DNA was extracted and submitted to SYBR Green I real-time PCR targeting the rgpB (P gingivalis), bspA (T forsythia), and rpoB (total bacteria) single copy genes. Results: Overall, R gingivalis, T forsythia, and the coexistence of both species were encountered in 28%, 66%, and 22% of the subjects, respectively. P gingivalis and T forsythia levels ranged from 5.65 x 10(-6) to 1.20 x 10(-2) and from 5.76 x 10(-6) to 1.35 x 10(-1). T forsythia was highly prevalent and numerous in the study groups, whereas P gingivalis was moderately frequent and less abundant, displaying 19-fold lower average levels than the former. Conclusions: The endodontic levels of P gingivalis and T forsythia, individually or in conjunction, did not display significant associations with the manifestation of pain of endodontic origin. (J Endod 2009,35:1518-1524)Brazilian funding agency Fundacao de Amparo a Pesquisa do Estado de Sao Paulo-FAPESP[04/01674-6]Brazilian funding agency Fundacao de Amparo a Pesquisa do Estado de Sao Paulo-FAPESP[04/13548-5

Identification of bacteria in endodontic infections by sequence analysis of 16S rDNA clone libraries

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOA significant proportion of oral bacteria are unable to undergo cultivation by existing techniques. In this regard, the microbiota from root canals still requires complementary characterization. The present study aimed at the identification of bacteria by sequence analysis of 16S rDNA clone libraries from seven endodontically infected teeth. Samples were collected from the root canals, subjected to the PCR with universal 16S rDNA primers, cloned and partially sequenced. Clones were clustered into groups of closely related sequences (phylotypes) and identification to the species level was performed by comparative analysis with the GenBank, EMBL and DDBJ databases, according to a 98% minimum identity. All samples were positive for bacteria and the number of phylotypes detected per subject varied from two to 14. The majority of taxa (65.2%) belonged to the phylum Firmicutes of the Gram-positive bacteria, followed by Proteobacteria (10.9%), Spirochaetes (4.3%), Bacteroidetes (6.5%), Actinobacteria (2.2%) and Deferribacteres (2.2%). A total of 46 distinct taxonomic units was identified. Four clones with low similarity to sequences previously deposited in the databases were sequenced to nearly full extent and were classified taxonomically as novel representatives of the order Clostridiales, including a putative novel species of Mogibacterium. The identification of novel phylotypes associated with endodontic infections suggests that the endodontium may still harbour a relevant proportion of uncharacterized taxa.A significant proportion of oral bacteria are unable to undergo cultivation by existing techniques. In this regard, the microbiota from root canals still requires complementary characterization. The present study aimed at the identification of bacteria by sequence analysis of 16S rDNA clone libraries from seven endodontically infected teeth. Samples were collected from the root canals, subjected to the PCR with universal 16S rDNA primers, cloned and partially sequenced. Clones were clustered into groups of closely related sequences (phylotypes) and identification to the species level was performed by comparative analysis with the GenBank, EMBL and DDBJ databases, according to a 98 % minimum identity. All samples were positive for bacteria and the number of phylotypes detected per subject varied from two to 14. The majority of taxa (65·2 %) belonged to the phylum Firmicutes of the Gram-positive bacteria, followed by Proteobacteria (10·9 %), Spirochaetes (4·3 %), Bacteroidetes(6·5 %), Actinobacteria (2·2 %) and Deferribacteres (2·2 %). A total of 46 distinct taxonomic units was identified. Four clones with low similarity to sequences previously deposited in the databases were sequenced to nearly full extent and were classified taxonomically as novel representatives of the order Clostridiales, including a putative novel species of Mogibacterium. The identification of novel phylotypes associated with endodontic infections suggests that the endodontium may still harbour a relevant proportion of uncharacterized taxa551101107FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO2004/01674-6, 2004/13548-5, 2000/10168-6sem informaçãosem informaçã