Arlem Nascimento de Oliveira

Rhizobia amylase production using various starchy substances as carbon substrates

Six isolates of indigenous rhizobia of Central Amazonia were screened for the production of amylases in liquid media using various starchy substances as carbon sources. All rhizobia strains could produce more extracellular protein, biomass and amylases with the different kinds of carbon substrates. Among the carbon sources tested maltose was the best substrate for protein and amylase production. In general, peach palm flour and corn starch (maizena®) were also considered to be good carbon sources for rhizobia amylases. On the other hand, the biomass production by the rhizobia isolates was higher in the presence of oat flour. INPA strain R-926 was a good amylase producer in maltose (1.94 U) and corn starch (0.53 U) media. INPA strain R-991 was also a good amylase producer in maltose (1.66 U) and corn starch (1.59 U) yielding significant extracellular amylase. Correlation analysis showed significant and positive relationships between rhizobia amylases and final pH (r = 0.49, P < 0.05), extracellular protein (r = 0.47, P < 0.47) and biomass production (r = 0.69, P < 0.01) in the maltose medium. The results obtained in this study revealed several Central Amazonian rhizobia strains as promising sources of amylase for biotechnological applications, especially in starch industry.

Seasonal dynamics of arbuscular mycorrhizal fungi in plants of Theobroma grandiflorum Schum and Paullinia cupana Mart. of aN agroforestry system in Central Amazonia, Amazonas State, Brazil

The seasonal dynamics of Arbuscular Mycorrhizal Fungi (AMF) was investigated in the rhizosphere of two fruit species in a terra firme (upland) ecosystem in Central Amazonia. Two host species (Theobroma grandiflorum and Paullinia cupana) and nine sampling months (August, September and December/1998, February, April, May and December/1999, February and May/2000) were studied in a completely randomized design, with five replications, set in a 2 x 9 factorial experiment. Soil (0-20 cm depth) and root samples were collected between August 1998 and May 2000. The mean percent colonization of AMF for both species reached maximal values in February and May 2000 (rainy season). In April and May 1999, February and May 2000 (rainy season) the highest AMF spore numbers were registered. The pluvial precipitation was significantly positively correlated with AMF number spores for both fruit species, and significant positive correlation only with AMF colonization of P. cupana. Soil moisture content was positively correlated with colonization and spore numbers of AMF for both species evaluated. AMF colonization and AMF spore numbers of T. grandiflorum were positively correlated with soil Mg and K concentrations. AMF spore numbers of T. grandiflorum were also negatively correlated with effective cation exchange capacity (ECEC). AMF colonization and AMF spore numbers in the rhizosphere of P. cupana were positively correlated with pH and Mn concentrations. AMF colonization was also positively correlated with AMF spore numbers for both species evaluated. In conclusion, this study showed that AMF colonization and sporulation are seasonal and dependent on host plant species, pluvial precipitation, soil moisture content and soil chemistry in Central Amazonia conditions.

Partial characterization of amylases of two indigenous Central Amazonian rhizobia strains

A producao e parcial caracterizacao de extratos brutos de amilase de duas estirpes de rizobio (R-926 e R-991) foram avaliadas. Para ambas as estirpes, as maximas atividades amiloliticas foram obtidas no inicio/meio da fase exponencial de crescimento. As amilases rizobiais foram ativas numa variacao de pH de 4,5 a 8,5 e temperatura de 30 a 50 oC. Nenhum dos ions testados (K+, Na+, Ca2+, Hg2+, Mg2+, Mn2+, Cu2+ e Zn2+) foi exigido para a atividade catalitica da estirpe R-926. A amilase produzida pelo R991 foi estimulada na presenca de K+, Hg2+ e Zn2+. Os surfactantes SDS, Triton X-100 e Tween-80 nao exerceram um pronunciado efeito inibitorio sobre as atividades enzimaticas, e SDS e Tween-80 causaram os maiores efeitos estimulatorios. A atividade amilolitica rizobial foi reduzida em ate 30% na presenca de EDTA; a amilase produzida pela estirpe R-926 tambem foi inibida pelo HgCl2, sugerindo, ao menos em parte, a importância de Ca2+ e residuos de cisteina na atividade amilolitica dessa estirpe.

Atividade enzimática de isolados de rizóbia nativos da Amazônia Central crescendo em diferentes níveis de acidez

A importância das bacterias conhecidas como rizobia no estabelecimento de leguminosas tem sido amplamente reconhecida. Porem, poucas sao as informacoes referentes ao perfil enzimatico dessas bacterias beneficas. O estudo objetivou investigar a influencia do pH do meio solido sobre a atividade enzimatica de rizobios nativos da Amazonia Central. Essa triagem constitui o primeiro passo no processo de selecao de microorganismos beneficos, como produtores de enzimas de aplicacao biotecnologica. Nesse estudo, 64 isolados de rizobia foram testados para a producao extracelular de amilase, lipase, pectinase e protease, em meio YMA modificado. Excetuando a atividade pectinolitica, todas as outras enzimas (amilase, lipase e protease) foram detectadas nos isolados investigados. Dois isolados (INPA R-975 e INPA R-926) exibiram atividades amiloliticas, lipoliticas e proteoliticas. Os indices enzimaticos amiloliticos e proteoliticos variaram significativamente entre os isolados e as condicoes de pH do meio de cultura. De maneira geral, as maiores atividades amiloliticas e proteoliticas foram exibidas pelos isolados INPA R-957, INPA R-915B e INPA R-991 em pH 6,5. O isolado INPA R-957 tambem se mostrou amilolitico e proteolitico nos pHs 5,0 e 8,0. Esse estudo mostrou que alguns rizobios nativos da Amazonia representam fontes promissoras de amilase e protease de uso biotecnologico, sobretudo na tecnologia de alimentos.

Enzimas hidrolíticas extracelulares de isolados de rizóbia nativos da Amazônia Central, Amazonas, Brasil

Legumes enrich the soil by contributing nitrogen through symbiotic biological nitrogen fixation by rhizobia bacteria. However, very little is known about the extracellular enzymatic profile of these microorganisms. In this context, the production of extracellular hydrolytic enzymes by indigenous strains of rhizobia in Central Amazonia was evaluated. This screening constitutes the first step in selecting indigenous microorganisms that are potentially exploitable as enzyme producers. Indigenous strains of rhizobia were screened for extracellular amylolytic, carboxymethylcellulolytic, lactolytic, lipolytic, pectinolytic and proteolytic activities on modified YMA. Ureolytic activity was detected on a urea-agar slant. Rhizobia strains isolated from cowpea nodules produced more enzymes than those isolated from soybean nodules. Out of all the extracellular hydrolytic enzymes evaluated, only pectinase was not detected in this study. The most frequent rhizobia enzymes were amylase (32.8%), protease (28.4%), urease (20.9%) and carboxymethylcellulase (9.0%). In this study, only amylase and protease enzymes varied significantly among rhizobia strains. INPA strains R-926 and R-915 showed the highest enzymatic levels for amylase (EI = 3.1) and protease (EI = 6.6), respectively. This paper showed some indigenous strains of rhizobia from Central Amazonia as promising sources of industrially relevant enzymes for biotechnological purposes.

Associação micorrízica e teores de nutrientes nas folhas de cupuaçuzeiro (Theobroma grandiflorum) e guaranazeiro (Paullinia cupana) de um sistema agroflorestal em Manaus, Amazonas

Arbuscular mycorrhiza can be important for plant nutrition in acid and low fertility soils such as those of the Amazon. The present study evaluated the mycorrhizal colonization by native arbuscular mycorrhizal fungi (AMF) and nutrient concentrations of cupuassu and guarana leaves in an agroforestry system in Manaus, Amazonas State, Brazil. Ten plants of each species were selected, of which the roots, soil and leaves were sampled during the rainy and dry seasons. Guarana and cupuassu trees presented higher levels of AMF colonization during the rainy season. Ca, Mg, K, P, Zn, Cu, and Mn concentrations in both species were not affected by the season. Fe concentration was higher during the rainy season in the cupuassu leaves, but higher in the dry season in the guarana leaves. Mycorrhizal colonization correlated with Ca, Mg, P, and Cu concentrations in cupuassu plants and with Ca, Fe, Zn, and Cu in guarana plants.

Influence of edapho-climatic factors on the sporulation and colonization of arbuscular mycorrhizal fungi in two Amazonian native fruit species

Arbuscular mycorrhizal fungi (AMF) colonization and spore numbers in the rhizosphere of two fruit species, Paullinia cupana Mart. and Theobroma grandiflorum Schum., growing in a terra firme ecosystem in Central Amazonia were studied from August 1998 to May 2000. Climatic and edaphic factors were also determined to investigate their influence on mycorrhizal variables. Soil pH, Al, Mn and effective cation exchange capacity exhibited seasonal variations during the investigation period. Temporal variations in mycorrhizal colonization levels and spore numbers occurred, indicating seasonality. Moreover, the patterns of mycorrhizal colonization levels and spore numbers for both host species were similar during the studied period. Mycorrhizal variables were related to climatic and edaphic factors, however, the intensity and type of influence of climatic and soil characteristics on AMF development tended to vary with the season and host plant species in Central Amazonia conditions.

Colonização micorrízica e concentração de nutrientes em três cultivares de bananeiras em um latossolo amarelo da Amazônia central

A adaptacao das plantas a baixa fertilidade dos solos amazonicos e uma alternativa de baixo insumo que satisfaz a maioria dos produtores regionais. Essa adaptacao pode estar relacionada as micorrizas arbusculares, que podem aumentar a capacidade das plantas em absorverem os nutrientes do solo. O estudo foi conduzido num plantio de bananeiras sobre um Latossolo amarelo na Faculdade de Ciencias Agrarias (Fundacao Universidade do Amazonas), objetivando verificar a colonizacao de fungos micorrizicos e teores de nutrientes foliares das cultivares de bananeira Maca, Pacovan e Prata, durante tres meses de avaliacoes (Dezembro/98, Janeiro e Fevereiro/99). Coletou-se amostras de raizes para avaliar as taxas de colonizacao e amostras foliares para verificar os teores de macro e micronutrientes. As medias da colonizacao radicular por fungos micorrizicos foram de 60,7% na cultivar Maca, 55,2% na Pacovan e 53,6% na Prata. Na amostragem feita em dezembro de 1998, a cultivar Maca apresentou menor colonizacao micorrizica (48,3% das raizes), do que a Pacovan (73,6%) e Prata (67,8%). No mes de janeiro de 1999 essa situacao se inverteu: a Maca apresentou a maior colonizacao micorrizica (75,3%) quando comparada com a da Pacovan (47,8%) e Prata (40,3%). As cultivares nao apresentaram diferencas entre si quanto as concentracoes de P e Fe, mas houve uma variacao significativa entre elas quanto aos teores de Ca, Mg, K, Zn, Cu e Mn. A colonizacao radicular por fungos micorrizicos correlacionou-se positivamente com os teores de Ca, K e Zn na cultivar Maca e, Cu na cultivar Prata. Estas correlacoes positivas permitem inferir que a associacao micorrizica foi importante no estimulo as absorcoes de Ca, K e Zn pela cultivar Maca e Cu pela Prata nas bananeiras de cinco anos na fase de producao comercial.

Efetividade de rizóbios e caracterização fenotípica dos isolados que nodulam feijão-caupi em solos da Amazônia Central

Cowpea (Vigna unguiculata) is an important legume cultivated in central Amazonia, but its rhizobia have been little studied. The present study aimed to evaluate the effectiveness and to characterize phenotypically the population of indigenous rhizobia that infect cowpea in the region. The rhizobia population from Novo Ayrao soils provided the highest shoot, root and total dry matter yields, number of nodules and nodule dry weights in cowpea plants; however, they were not different from those found for the control treatment with N. Based on phenotypic criteria, it was possible to identify a wide diversity of populations of rhizobia contained in Amazonian soils.

Influência do pH e temperatura sobre a atividade amilolítica de rizóbios isolados de solos da Amazônia

Poucas sao as informacoes referentes ao perfil enzimatico de bacterias rizobiais. Em meio de cultura solidificado, foi conduzido um experimento em fatorial 7 x 3 x 3 para avaliar o efeito do pH (5,0; 6,5 e 8,0) e da temperatura (25, 35 e 42 oC) sobre a atividade amilolitica de sete isolados de rizobio. As maiores atividades amiloliticas foram observadas em ambientes acidos, com algumas bacterias tambem produzindo niveis significativos em pH 8,0. Entre as interacoes significativas (P<0,01), os isolados INPA R-110 e R-822 apresentaram maximas atividades em pH 5,0 e 25 oC, com o R-822 tambem sendo um bom produtor de amilase nas temperaturas de 35 e 42 oC. Em termos gerais, os isolados INPA R-110 e R-822 foram os melhores produtores de amilases, com atividades enzimaticas maiores do que 2,0.