Marcelo Ferreira Fernandes

Atributos físicos, químicos e biológicos de um Latossolo de cerrado em plantio de espécies florestais

The objective of this study was to evaluate the impact forest plantations on physical, chemical and microbiological attributes a cerrado Oxisol. Soil samples were collected at 0-10 cm depth from sites cultivated with pinus (Pinus tecunumanii), eucalyptus (Eucalyptus grandis) and carvoeiro (Sclerolobium paniculatum) for over 20 years. An adjacent native cerrado area was used as a reference of the original soil conditions. It was observed in relation to the native cerrado: increases in soil density under pinus and eucalyptus, reduction in the macroporosity under pinus, lower organic matter contents under pinus and eucalyptus, besides decreases in the soil pH and in the base saturation under pinus and carvoeiro along with an increase in aluminum saturation. Soil microbial biomass carbon under the pinus, eucalyptus and carvoeiro sites was about half of that found under cerrado. The activities of acid phosphatase and arylsulfatase were inhibited by pinus and stimulated by carvoeiro. Among the forest systems evaluated, pinus promoted the greatest reduction on soil quality. The microbiological variables were the most sensitive to detect the effects of these systems on soil quality.

Fitomassa de adubos verdes e controle de plantas daninhas em diferentes densidades populacionias de leguminosas

-2 ), e o crescimento de plantas daninhas nessas densidades, em area de tabuleiros costeiros. O experimento foi desenvolvido de maio a agosto de 1996, no Campo Experimental “Antonio Martins” (EMDAGRO/Embrapa-CPATC), em Lagarto, SE. O numero de plantas vivas na floracao (NPVF) e a materia seca da parte aerea das leguminosas (MSPA) foram determinados quando, em cada especie, cerca de 50% das plantas floresceram. Maiores incrementos de MSPA, em resposta ao adensamento populacional, foram observados em C. spectabilis e C. breviflora, seguidas pelo calopogonio, mucuna-preta e mucuna-rajada. Em relacao ao feijao-de-porco, a resposta foi negativa, enquanto com o guandu nao houve influencia. Quanto ao NPVF, as respostas ao adensamento foram lineares e positivas em C. spectabilis, C. breviflora e calopogonio, e quadraticas com ponto de maxima em feijao-de-porco, guandu e mucuna-rajada. Embora nenhum modelo tenha sido ajustado para expressar a relacao entre NPVF e adensamento na semeadura de mucuna-preta, a sobrevivencia dessa especie foi reduzida em todas as densidades. Maiores inibicoes de plantas daninhas ocorreram nas parcelas de mucuna-preta e feijao-de-porco.

Seleção de rizóbios nativos para guandu, caupi e feijão-de-porco nos tabuleiros costeiros de Sergipe

Abstract€–€The inoculation of rhizobial strains in jackbean ( Canavalia ensiformis ), cowpea ( Vignaunguiculata ) and pigeonpea ( Cajanus cajan ), recommended for other regions of Brazil, has not resultedin increases of biological nitrogen fixation rates and plant growth in soils of the coastal tableland ofSergipe (Brazilian Northeast). The objectives of this work were to evaluate the symbiotic effectivenessof indigenous rhizobia from that coastal tableland associated to these three legumes and their toleranceto stresses. Seventeen rhizobia strains were isolated and evaluated in a greenhouse. Four strains wereselected for pigeonpea; seven for cowpea and three for jackbean. Nodules number and dry weight wererelated to shoot dry weight, leaf area and leaf N€content, in all three legumes. The same strains wereefficient for both cowpea and pigeonpea. Three pigeonpea (R35, R43 and R45) and two cowpea (R10and R17) rhizobia were characterized in€vitro and all showed tolerance to high levels of nalidix acid,chloramphenicol and tetracycline; however, they were sensitive to streptomycin and kanamycin. Allstrains were able to grow at€35oC and, except for R17, were tolerant to aluminium (10€mg€L

Comparison of Whole-Cell Fatty Acid (MIDI) or Phospholipid Fatty Acid (PLFA) Extractants as Biomarkers to Profile Soil Microbial Communities

The whole-cell lipid extraction to profile microbial communities on soils using fatty acid (FA) biomarkers is commonly done with the two extractants associated with the phospholipid fatty acid (PLFA) or Microbial IDentification Inc. (MIDI) methods. These extractants have very different chemistry and lipid separation procedures, but often shown a similar ability to discriminate soils from various management and vegetation systems. However, the mechanism and the chemistry of the exact suite of FAs extracted by these two methods are poorly understood. Therefore, the objective was to qualitatively and quantitatively compare the MIDI and PLFA microbial profiling methods for detecting microbial community shifts due to soil type or management. Twenty-nine soil samples were collected from a wide range of soil types across Oregon and extracted FAs by each method were analyzed by gas chromatography (GC) and GC-mass spectrometry. Unlike PLFA profiles, which were highly related to microbial FAs, the overall MIDI-FA profiles were highly related to the plant-derived FAs. Plant-associated compounds were quantitatively related to particulate organic matter (POM) and qualitatively related to the standing vegetation at sampling. These FAs were negatively correlated to respiration rate normalized to POM (RespPOM), which increased in systems under more intensive management. A strong negative correlation was found between MIDI-FA to PLFA ratios and total organic carbon (TOC). When the reagents used in MIDI procedure were tested for the limited recovery of MIDI-FAs from soil with high organic matter, the recovery of MIDI-FA microbial signatures sharply decreased with increasing ratios of soil to extractant. Hence, the MIDI method should be used with great caution for interpreting changes in FA profiles due to shifts in microbial communities.

Fatty acid profiles in Leishmania spp. isolates with natural resistance to nitric oxide and trivalent antimony

Fatty acids, especially those from phospholipids (PLFA), are essential membrane components that are present in relatively constant proportions in biological membranes under natural conditions. However, under harmful growth conditions, such as diseases, environmental changes, and chemical exposure, the fatty acid proportions might vary. If such changes could be identified and revealed to be specific for adverse situations, they could be used as biomarkers. Such biomarkers could facilitate the identification of virulence and resistance mechanisms to particular chemotherapeutic agents. Therefore, specific biomarkers could lead to better therapeutic decisions that would, in turn, enhance treatment effectiveness. The objective of this study was to compare the fatty acid profiles of trivalent antimony and nitric oxide (NO)-resistant and -sensitive Leishmania chagasi and Leishmania amazonensis isolates. Fatty acid methyl esters (FAMEs) were obtained from total lipids (MIDI), ester-linked lipids (ELFA), and ester-linked phospholipids (PLFA). FAMEs were analyzed by chromatography and mass spectrometry. Species- or resistance-associated differences in FAME profiles were assessed by nonmetric multidimensional scaling, multiresponse permutation procedures, and indicator species analyses. The isolate groups had different MIDI-FAME profiles. However, neither the ELFA nor PLFA profiles differed between the sensitive and resistant isolates. Levels of the fatty acid 18:1 Δ9c were increased in sensitive isolates (p < 0,001), whereas the fatty acid 20:4 Δ5,8,11,14 showed the opposite trend (p < 0.01). We conclude that these two fatty acids are potential biomarkers for NO and antimony resistance in L. chagasi and L. amazonensis and that they could be helpful in therapeutic diagnoses.

Soil attributes under agroecosystems and forest vegetation in the coastal tablelands of northestern Brazil Atributos de solo de agroecossistemas e coberturas florestais dos tabuleiros costeiros do nordeste do Brasil

This study evaluated the changes occurred in a set of soil attributes, particularly those related to the dynamics of soil organic carbon (SOC), as a function of the replacement of native forest for agricultural ecosystems of regional importance in the coastal tablelands of Northeastern Brazil (orange, coconut, eucalyptus and sugarcane). Six commercial sites under these agroecosystems were compared to neighboring areas of native forest in five areas along this region (Coruripe, Umbauba, Acajutiba, Cruz das Almas and Nova Vicosa). Soil samples were taken from 0-5 and 5-20 cm depth and analyzed for particle size distribution, bulk density, organic C (OC), particulate organic matter, C in soil solution, microbial biomass C, total cation exchange capacity and water stable aggregates. Linear correlation and multivariate techniques were used for data analysis. The values of base saturation and Al saturation for the 0-20 cm depth layer were also calculated. In all the studied areas, soils under native forest presented better status of physical and chemical attributes than their agroecosystem counterparts, especially in the 0-5 cm layer. For both layers, OC content was the attribute most strongly correlated with the overall changes in all attributes. Unexpectedly, the OC content showed no significant correlation with the sum of silt and clay contents. The set of variables investigated in this study is sensitive to differentiate the quality of soils under perennial and semi-perennial land uses from their counterparts under natural vegetation in the landscapes of the coastal tablelands of Northeastern Brazil.

Toxicidade de herbicidas utilizados na cultura da cana-de-açúcar à bactéria diazotrófica Azospirillum brasilense

The objective of this work was to identify the herbicides applied on sugarcane that do not affect the growth nor the process of biological nitrogen fixation (BNF) of the diazotrophic bacterium Azospirillum brasilense. Commercial doses of eighteen herbicides (paraquat, ametryn, amicarbazone, diuron, metribuzin [hexazinone + diuron] [hexazinone + clomazone] clomazone, isoxaflutole, sulfentrazone, oxyfluorfen, imazapic, imazapyr, [trifloxysulfuron-sodium + ametryn], S-metolachlor, glyphosate, MSMA and 2,4-D) were tested regarding their impact on the bacterial growth in liquid DIG medium. Thus, the carrying capacity of the culture medium, duration of lag phase and generation time of A. brasilense were determined by calculating the optical density data obtained at regular intervals during the incubation of the cultures for 55 h. The impact of herbicides on nitrogenase activity of A. brasilense was evaluated in semi-solid N-free NFB me dium by acetylene reduction assay (ARA). The effects of herbicides on the growth variables and ARA were compared with the control by the Dunnett test. Paraquat, oxyfluorfen, [trifloxysulfuron -sodium + ametryn] and glyphosate reduced the carrying capacity of DIG medium with respect to A. brasilense growth. This effect was associated with increases in both the length of the lag phase and generation time for [trifloxysulfuron-sodium + ametryn], and with the increase in gene ration time for glyphosate. MSMA, paraquat and amicarbazone reduce the BNF of A. brasilense; however, this reduction is more severe in the presence of paraquat. The other herbicides do not affect the growth or the BNF of A. brasilense.

Estrutura metabólica e genética de comunidades bacterianas em solo de cerrado sob diferentes manejos

O objetivo deste trabalho foi avaliar a estrutura metabolica e genetica de comunidades bacterianas em Latossolo de cerrado sob vegetacao nativa ou cultivado em sistema de rotacao soja/milho sob preparo convencional e plantio direto. Foram utilizadas microplacas EcoPlate para determinar o perfil e a diversidade metabolica das comunidades bacterianas, e eletroforese em gel com gradiente desnaturante (DGGE) para avaliar a estrutura genetica. O teste estatistico de Mantel foi utilizado para avaliar a relacao entre a estrutura metabolica e a genetica. A comunidade bacteriana sob vegetacao nativa apresentou perfil metabolico diferente do encontrado em solos cultivados. No solo cultivado com soja sob preparo convencional, o padrao de utilizacao das fontes de carbono diferenciou-se dos demais tratamentos. Com base nos resultados de DGGE, a comunidade bacteriana sob vegetacao nativa apresentou 35% de similaridade com as de areas cultivadas. Foram formados grupos distintos de comunidades bacterianas do solo entre as areas sob preparo convencional e plantio direto. Houve correlacao significativa de 62% entre as matrizes geradas pelas microplacas EcoPlate e pela DGGE. Variacoes no perfil metabolico estao relacionadas as variacoes na estrutura genetica das comunidades bacterianas do solo.

Antimicrobial potential of Actinomycetes by NRPS and PKS-I pathways

BackgroundActinomycetes may account for 10 to 30% of the totalsoil rhizosphere microorganisms. The attention given tothe actinomycetes in biotechnological applications is aresult of their metabolic versatility that is accompaniedby the production of primary and secondary metabolitesof economic importance, which are a promising source ofproducts (e.g., antibiotics, enzyme inhibitors, antiparasiticand anticancer agents) [1,2]. Included in this range ofcompounds are secondary metabolites synthesized bypolyketide synthase (PKS) and non-ribosomal peptidesynthetase (NRPS) pathways. An effective method forassessing the presence of these biosynthetic pathways isthe detection of PKS and NRPS genes by PCR [3,4].Thus, this study was based on targeted analyses of 31 soilisolate actinomycetes aiming to evaluate their antimicro-bial potential through the NRPS and PKS-I pathways.MethodsThe antimicrobial activity was evaluated by the antagon-ism test against two economically important phyto-pathogens, the bacterium Xanthomonas campestris andthe fungus Thielaviopsis paradoxa,usingthetechniqueof double layer. TheX. campestris and T. paradoxawere propagated at 28°C in YM (yeast malt) pH 6.0 andPDB (potato dextrose broth) respectively. The resultswere statistically analyzed using the Bonferroni test.The presence of genes PKS and NRPS was evaluatedby PCR, using degenerate primers for highly conservedregions encoding enzymes associated with biosynthesisof polyketides and peptides.Results and conclusionsAccording to the experimental results, 52% of the iso-lates showed antimicrobial activity against at least oneof the target bacterial pathogens tested. Among theseactive isolates, some belong to rare families. Thus, thisfinding can be a source of novel biomolecules with anti-microbial activity. From those isolates that presentedone of the NRPS and PKS-I genes, 75% of them showedantagonistic activity against one of the phytopathogensevaluated. Preliminary data on this screening demon-strate the importance of the biotechnological potentialof these actinomycetes due to the antagonistic activityagainst plant pathogens of economic interest and thepossibility of be used as biocontrol, besides offering astrong area for metabolic research [2,5].

Rainfall and Coconut Accession Explain the Composition and Abundance of the Community of Potential Auchenorrhyncha Phytoplasma Vectors in Brazil

Abstract Coconut plantations are attacked by the lethal yellowing (LY), which is spreading rapidly with extremely destructive effects in several countries. The disease is caused by phytoplasmas that occur in the plant phloem and are transmitted by Haplaxius crudus (Van Duzee) (Auchenorrhyncha: Cixiidae). Owing to their phloem-sap feeding habit, other planthopper species possibly act as vectors. Here, we aimed at assessing the seasonal variation in the Auchenorrhyncha community in six dwarf coconut accessions. Also, we assessed the relative contribution of biotic (coconut accession) and abiotic (rainfall, temperature) in explaining Auchenorrhyncha composition and abundance. The Auchenorrhyncha community was monthly evaluated for 1 yr using yellow sticky traps. Among the most abundant species, Oecleus sp., Balclutha sp., Deltocephalinae sp.2, Deltocephalinae sp.3, Cenchreini sp., Omolicna nigripennis Caldwell (Derbidae), and Cedusa sp. are potential phytoplasma vectors. The composition of the Auchenorrhyncha community differed between dwarf coconut accessions and periods, namely, in March and April (transition from dry to rainy season) and August (transition from rainy to dry season). In these months, Oecleus sp. was predominantly found in the accessions Cameroon Red Dwarf, Malayan Red Dwarf, and Brazilian Red Dwarf Gramame, while Cenchreini sp. and Bolbonota sp. were dominant in the accessions Brazilian Yellow Dwarf Gramame, Malayan Yellow Dwarf, and Brazilian Green Dwarf Jequi. We conclude that dwarf coconut host several Auchenorrhyncha species potential phytoplasma vectors. Furthermore, coconut accessions could be exploited in breeding programs aiming at prevention of LY. However, rainfall followed by accessions mostly explained the composition and abundance of the Auchenorrhyncha community.