Enxofre na agricultura

Sulfur (S) deficiency in soils is becoming increasingly common in many areas of the world as a result of agronomic practices, high biomass exportation and reduced S emissions to the atmosphere. In this review, the incidence and commercial exploitation of S pools in nature are discussed, as well as the importance of S for plants and the organic and inorganic S forms in soil and their transformations, especially the process of microbiological oxidation of elemental sulfur (S0) as an alternative to the replenishment of S levels in the soil. The diversity of S0-oxidizing microorganisms in soils, in particular the genus Thiobacillus, and the biochemical mechanisms of S0 oxidation in bacteria were also addressed. Finally, the main methods to measure the S0 oxidation rate in soils and the variables that influence this process were revised.We would like to thank the State of São Paulo Research Foundation (FAPESP) for\ud funding this project. \ud

Cloning and analysis of the gene that codifies for the acetolactate synthase enzyme of Amaranthus quitensis and Bidens pilosa

A enzima Acetolactato sintase é a enzima chave na biossíntese dos aminoácidos de cadeia ramificada valina, leucina e isoleucina. A ALS foi identificada como alvo de ação de cinco classes distintas de herbicidas: sulfoniluréias, imidazolinonas, triazolopirimidinas, pirimidil-tiobenzoatos e sulfonilamino-carbonil-triazolinonas. Estes herbicidas vêm sendo intensivamente utilizados no controle de plantas daninhas em diversos países, levando ao surgimento de biótipos resistentes. Até hoje foram observadas 83 espécies resistentes aos herbicidas inibidores da ALS no mundo. Na América do Sul, foram identificadas as espécies Bidens pilosa (picão-preto) e Amaranthus quitensis (caruru), no Brasil e na Argentina, respectivamente. Sementes destas espécies foram coletadas em lavouras de soja para ensaios biológicos e determinação da curva dose-resposta, confirmando a resistência e sensibilidade aos herbicidas inibidores da ALS. A seqüência codificadora do gene da ALS de cinco plantas, dos biótipos resistentes e sensíveis, de ambas as espécies, foi amplificada por PCR, clonada em plasmídeos e seqüenciada. Os resultados mostram que a seqüência codificadora do gene da ALS em A. quitensis é composta por 2010 nucleotídeos tanto nos biótipos resistentes como nos sensíveis. Em B. pilosa, a seqüência dos biótipos resistentes é composta por 1935 nucleotídeos e dos biótipos sensíveis é composta por 1959 nucleotídeos. Foi demonstrado que o fenótipo de resistência em ambas as espécies é determinado pela substituição do aminoácido Triptofano (W), nos biótipos sensíveis, pelo aminoácido Leucina (L), nos biótipos resistentes, na região denominada domínio B. Resultados semelhantes foram descritos em outras espécies. Plasmídeos binários contendo a seqüência codificadora completa da ALS, de biótipos resistentes e sensíveis de A. quitensis e B. pilosa, foram construídos para a transformação de discos foliares de tabaco via Agrobacterium tumefasciensAcetolactate synthase (ALS) is the key enzyme in the biosynthesis of branched chain amino acids: valine, leucine and isolucine. ALS has been identified as the site of action to five distinct classes of herbicides: sulfonylureas, imidazolinones, triazolopyrimidines, pyrimidinyl thiobenzoates and sulfonylamino-carbonyl-triazolinones. These herbicides have been used intensively to control weed plants in many countries, increasing the appearance of herbicide resistant biotypes. Until today, it has been observed eighty three ALS inhibitors herbicides resistant species in the world. In South America, resistant biotypes of Bidens pilosa (hairy beggarticks) and Amaranthus quitensis(pigweed) were identified in Brazil and Argentina, respectively. Seeds of these species were harvested from soybean fields for bioassays and dose-response curve to confirm resistance and sensitivity to herbicides inhibitors of ALS. The coding region sequence of the ALS gene of five plants from resistant and sensitive biotypes of both species were amplified by PCR, cloned into plasmids and sequenced. The data shows that the A. quitensis coding region of the ALS gene is composed by 2010 nucleotides of both resistant and sensitive biotypes. In B. pilosa, the resistant biotype is composed by 1935 nucleotides and the sensitive one is composed by 1959 nucleotides. It was demonstrated that the resistance phenotype in both species is due to a Tryptophane (W) aminoacid exchange, in the sensitive ecotype, to a Leucine (L) in the resistant one, at the domain B region. Similar results has been described for others resistant species. Binary plasmids were constructed containing the complete codified ALS sequence of A. quitensis and B. pilosa of resistant and sensitive biotypes to transform tobacco leaves by Agrobacterium tumefascien

Microbiological elemental sulfur oxidation in soil

Reduções dos níveis de sulfato nos solos vêm sendo observadas em função de práticas agrícolas e exportação de biomassa. O enxofre Elementar (S0) pode ser usado como fertilizante, contudo para ser absorvido pelas plantas deve ser antes oxidado a sulfato. A oxidação microbiológica do S0 está associada com Acidithiobacillus thiooxidans, apesar de muitos trabalhos não detectarem esta espécie nos solos. Trabalhos recentes têm mostrado uma grande diversidade de microrganismos capazes de oxidar o S0 no solo além do A. thiooxidans, entretanto, pouco se sabe sobre esta diversidade em solos brasileiros. Os objetivos deste trabalho foram determinar a taxa de oxidação do S0 em três solos brasileiros, a diversidade de Bacteria e Archaea envolvidas nesse processo, isolar bactérias oxidantes de enxofre (BOE) e avaliar seu potencial como biofertilizante. Amostras de solos foram coletadas em Anhembi/SP (ANB), Brasília, DF (BRA) e Rondonópolis, MT (RDP). Os solos foram enriquecidos com 10 g de S0 kg-1 (+S0) ou não (-S0) e incubados em microcosmos a 28 oC por 0, 6, 22, 38, 54, 67, 86 e 102 dias. A taxa de oxidação do S0 variou entre 2,8 e 3,2 ug S cm-2 dia-2 nos solos arenosos (ANB e RDP) e 1,3 ug S cm-2 dia-2 no solo argiloso (BRA) após 102 dias de incubação. A oxidação do S0 elevou a quantidade de sulfato e reduziu o pH principalmente nos solos arenosos. A aplicação do S0 alterou a estrutura e a diversidade da comunidade microbiana. Foram obtidas 811 seqüências do gene rRNA 16S de bactérias, sendo agrupadas em 518 Unidade Taxonômicas Operacionais (UTOs). Os principais filos nos solos foram Acidobacteria, Actinobacteria, Firmicutes e Proteobacteria. Foram obtidas 463 seqüências de rRNA 16S de Archaea, sendo agrupadas em 39 UTOs. Mais de 84% da UTOs foram classificadas como Archaea não classificadas enquanto 15% foram classificadas como Euryarchaeota. A diversidade de Archaea não foi muito afetada pelo S0. Cinqüenta BOE foram isoladas e afiliadas a Proteobacteria (68%), Actinobacteria (18%) e Firmicutes (14%) após o seqüenciamento do rRNA 16S. Os gêneros atribuídos foram: Aurantimonas, Acinetobacter, Novosphingobium, Methylobacterium. Paracoccus, Bradyrhizobium, Sphingomonas, Mycobacterium, Micrococcus e Bacillus. Esferas de alginato +S0, contendo os isolados de BOE ANB9 (Acinetobacter), RDP5 (Mycobacterium) e A. thiooxidans foram incubados em areia estéril, resultando no aumento de 111%, 430% e 5350% no SO4 2- comparado ao controle negativo após 14 dias de incubação, respectivamente. As taxas de oxidação do S0 foram 4,7 (ANB9), 18 (RDP5) e 130 (A. thiooxidans) vezes maiores do que o controle negativo após o mesmo período. As micro-esferas carregando as bactérias e o S0 foram incubadas nos solos ANB e BRA durante 54 dias. A. thiooxidans foi o oxidante de enxofre mais eficiente, apresentando a maior taxa de oxidação, aumento do SO4 2- e redução do pH em comparação com os outros isolados de BOE. As esferas de A. thiooxidans também foram capazes de solubilizar rocha fosfática. Novas informações foram geradas sobre a diversidade de bactérias envolvidas na oxidação do S0 em solos brasileiros.Depletion of sulfur levels in soil has been observed as a result of agricultural practices and biomass harvesting. Elemental sulfur (S0) may be an interesting fertilizer, however it must be oxidized to sulfate in order to be taken up by plants. Biological oxidation of S0 is commonly associated to Acidithiobacillus thiooxidans, although many studies failed to detect them in soils. Recent efforts have shown a great diversity of microorganisms able to oxidize S0, besides A. thiooxidans. Nevertheless, no information is available for Brazilian soils. The aims of this work were to determine the S0 oxidation rates of three Brazilian soils, the bacterial and archaeal communities diversity associated to S0 oxidation, as well as, to isolate sulfur oxidizing bacteria (SOB) and evaluate its potential as a biofertilizer. Soils sampled in Anhembi, SP (ANB), Brasília, DF (BRA) and Rondonópolis, MT (RDP) were enriched with 10 g of S0 kg-1 (+S0) or not (-S0) and incubated in microcosms for 0, 6, 22, 38, 54, 67, 86 and 102 days under 28 oC. Oxidation rates of S0 were low, ranging to 2,8 and 3,2 ug S cm-2 day-2 in the sand soils (RDP and BRA) and 1,3 ug S cm-2 day-2 in the clay one (BRA) after 102 days incubation. Soil SO4 2- content was increased and pH decreased as result of S0 oxidation mainly in the sand soils. Bacterial community structure and diversity were affected by S0 amendment and time of incubation, represented by changes in the DGGE profile and phylum distribution. Were obtained 811 bacterial 16S rRNA sequences, clustered in 518 Operational Taxonomic Units (OTUs). The predominant phyla in the soils were Acidobacteria, Actinobacteria, Firmicutes and Proteobacteria. Were obtained 463 archaeal 16S rRNA sequences clustered into 39 OTUs. More than 84% of the OTUs were assembled to unclassified Archaea whereas 15% were classified as Euryarchaeota. Archaea diversity was not mostly affected by S0. Fifty SOB were isolated and affiliated to Proteobacteria (68%), Actinobacteria (18%) and Firmicutes (14%) after 16S rRNA sequencing. The assigned genera were Aurantimonas, Acinetobacter, Novosphingobium, Methylobacterium, Paracoccus, Bradyrhizobium, Sphingomonas, Mycobacterium, Micrococcus and Bacillus. Alginate beads containing the SOB isolates ANB9 (Acinetobacter), RDP5 (Mycobacterium) and A. thiooxidans plus S0 were incubated in sterile sand resulting in 111%, 430% and 5350% increment in SO4 2- comparing to negative controls after 14 days incubation, respectively. The S0 oxidation rate was 4,7 (ANB9), 18 (RDP5) and 130 (A. thiooxidans) times greater than the negative control after the same time. The entrapped bacteria with S0 were incubated in ANB and BRA soils for 54 days in microcosms. A. thiooxidans was the best S0 oxidizer, showing the highest oxidation rate, increment in SO4 2- and pH decrease comparing with the other SOB isolates. A. thiooxidans beads were also able to solubilize phosphate rock. New information was generated about the bacterial diversity involved in the S0 oxidation in Brazilian soils

Cloning and analysis of the gene that codifies for the acetolactate synthase enzyme of Amaranthus quitensis and Bidens pilosa

A enzima Acetolactato sintase é a enzima chave na biossíntese dos aminoácidos de cadeia ramificada valina, leucina e isoleucina. A ALS foi identificada como alvo de ação de cinco classes distintas de herbicidas: sulfoniluréias, imidazolinonas, triazolopirimidinas, pirimidil-tiobenzoatos e sulfonilamino-carbonil-triazolinonas. Estes herbicidas vêm sendo intensivamente utilizados no controle de plantas daninhas em diversos países, levando ao surgimento de biótipos resistentes. Até hoje foram observadas 83 espécies resistentes aos herbicidas inibidores da ALS no mundo. Na América do Sul, foram identificadas as espécies Bidens pilosa (picão-preto) e Amaranthus quitensis (caruru), no Brasil e na Argentina, respectivamente. Sementes destas espécies foram coletadas em lavouras de soja para ensaios biológicos e determinação da curva dose-resposta, confirmando a resistência e sensibilidade aos herbicidas inibidores da ALS. A seqüência codificadora do gene da ALS de cinco plantas, dos biótipos resistentes e sensíveis, de ambas as espécies, foi amplificada por PCR, clonada em plasmídeos e seqüenciada. Os resultados mostram que a seqüência codificadora do gene da ALS em A. quitensis é composta por 2010 nucleotídeos tanto nos biótipos resistentes como nos sensíveis. Em B. pilosa, a seqüência dos biótipos resistentes é composta por 1935 nucleotídeos e dos biótipos sensíveis é composta por 1959 nucleotídeos. Foi demonstrado que o fenótipo de resistência em ambas as espécies é determinado pela substituição do aminoácido Triptofano (W), nos biótipos sensíveis, pelo aminoácido Leucina (L), nos biótipos resistentes, na região denominada domínio B. Resultados semelhantes foram descritos em outras espécies. Plasmídeos binários contendo a seqüência codificadora completa da ALS, de biótipos resistentes e sensíveis de A. quitensis e B. pilosa, foram construídos para a transformação de discos foliares de tabaco via Agrobacterium tumefasciensAcetolactate synthase (ALS) is the key enzyme in the biosynthesis of branched chain amino acids: valine, leucine and isolucine. ALS has been identified as the site of action to five distinct classes of herbicides: sulfonylureas, imidazolinones, triazolopyrimidines, pyrimidinyl thiobenzoates and sulfonylamino-carbonyl-triazolinones. These herbicides have been used intensively to control weed plants in many countries, increasing the appearance of herbicide resistant biotypes. Until today, it has been observed eighty three ALS inhibitors herbicides resistant species in the world. In South America, resistant biotypes of Bidens pilosa (hairy beggarticks) and Amaranthus quitensis(pigweed) were identified in Brazil and Argentina, respectively. Seeds of these species were harvested from soybean fields for bioassays and dose-response curve to confirm resistance and sensitivity to herbicides inhibitors of ALS. The coding region sequence of the ALS gene of five plants from resistant and sensitive biotypes of both species were amplified by PCR, cloned into plasmids and sequenced. The data shows that the A. quitensis coding region of the ALS gene is composed by 2010 nucleotides of both resistant and sensitive biotypes. In B. pilosa, the resistant biotype is composed by 1935 nucleotides and the sensitive one is composed by 1959 nucleotides. It was demonstrated that the resistance phenotype in both species is due to a Tryptophane (W) aminoacid exchange, in the sensitive ecotype, to a Leucine (L) in the resistant one, at the domain B region. Similar results has been described for others resistant species. Binary plasmids were constructed containing the complete codified ALS sequence of A. quitensis and B. pilosa of resistant and sensitive biotypes to transform tobacco leaves by Agrobacterium tumefascien

Fungal community assembly in the Amazonian Dark Earth

Here, we compare the fungal community composition and diversity in Amazonian Dark Earth (ADE) and the respective non-anthropogenic origin adjacent (ADJ) soils from four different sites in Brazilian Central Amazon using pyrosequencing of 18S ribosomal RNA (rRNA) gene. Fungal community composition in ADE soils were more similar to each other than their ADJ soils, except for only one site. Phosphorus and aluminum saturation were the main soil chemical factors contributing to ADE and ADJ fungal community dissimilarities. Differences in fungal richness were not observed between ADE and ADJ soil pairs regarding to the most sites. In general, the most dominant subphyla present in the soils were Pezizomycotina, Agaricomycotina, and Mortierellomycotina. The most abundant operational taxonomic units (OTUs) in ADE showed similarities with the entomopathogenic fungus Cordyceps confragosa and the saprobes Fomitopsis pinicola, Acremonium vitellinum, and Mortierellaceae sp., whereas OTUs similar to Aspergillus niger, Lithothelium septemseptatum, Heliocephala gracillis, and Pestalosphaeria sp. were more abundant in ADJ soils. Differences in fungal community composition were associated to soil chemical factors in ADE (P, Ca, Zn, Mg, organic matter, sum of bases, and base saturation) and ADJ (Al, potential acidity, Al saturation, B, and Fe) soils. These results contribute to a deeper view of the fungi communities in ADE and open new perspectives for entomopathogenic fungi studies

Rhizobacterial community structure differences among sorghum cultivars in different growth stages and soils

Plant genotype selects the rhizosphere microbiome. The success of plant–microbe interactions is dependent on factors that directly or indirectly influence the plant rhizosphere microbial composition. We investigated the rhizosphere bacterial community composition of seven different sorghum cultivars in two different soil types (abandoned (CF) and agricultural (VD)). The rhizosphere bacterial community was evaluated at four different plant growth stages: emergence of the second (day 10) and third leaves (day 20), the transition between the vegetative and reproductive stages (day 35), and the emergence of the last visible leaf (day 50). At early stages (days 10 and 20), the sorghum rhizosphere bacterial community composition was mainly driven by soil type, whereas at late stages (days 35 and 50), the bacterial community composition was also affected by the sorghum genotype. Although this effect of sorghum genotype was small, different sorghum cultivars assembled significantly different bacterial community compositions. In CF soil, the striga-resistant cultivar had significantly higher relative abundances of Acidobacteria GP1, Burkholderia, Cupriavidus (Burkholderiaceae), Acidovorax and Albidiferax (Comamonadaceae) than the other six cultivars. This study is the first to simultaneously investigate the contributions of plant genotype, plant growth stage and soil type in shaping sorghum rhizosphere bacterial community composition

Covellite (CuS) Production from a Real Acid Mine Drainage Treated with Biogenic H₂S

Acid Mine Drainage (AMD) is an environmental problem associated with mining activities, which resulted from the exposure of sulfur bearing materials to oxygen and water. AMD is a pollution source due to its extreme acidity, high concentration of sulfate, and soluble metals. Biological AMD treatment is one alternative to couple environmental amelioration for valuable dissolved metals recovery, as a new source of raw materials. Covellite (CuS) particles were synthetized from an AMD sample collected in a Brazilian copper mine, after 48 and 96 h of exposure to hydrogen sulfide (H2S) produced in a bioreactor containing acidophilic sulfate reducing bacteria (SRB). The time of exposure affected the morphology, nucleation, and size of CuS crystals. CuS crystals synthetized after 96 h of H2S exposure showed better ordination as indicated by sharp and intense diffractograms obtained by X-ray diffraction (XRD), and the predominance of placoid sheets with hexagonal habit structure as observed by scanning electrons microscopy (SEM). Energy dispersive X-ray fluorescence (EDXRF) spectrometry indicated a Cu:S molar ratio in agreement with CuS. Granulometric analysis demonstrated that 90% of CuS particles were less than 22 µm size. AMD biological treatment is a potential economical CuS recovery option for metallurgical process chain incorporation, or new industrial applications, since the alteration of synthesis conditions can produce different crystal forms with specific characteristics

Bioleaching for Copper Extraction of Marginal Ores from the Brazilian Amazon Region

The use of biotechnology to explore low-grade ore deposits and mining tailings is one of the most promising alternatives to reduce environmental impacts and costs of copper extraction. However, such technology still depends on improvements to be fully applied in Brazil under industrial scale. In this way, the bioleaching, by Acidithiobacillus ferrooxidans, in columns and stirred reactors were evaluated regarding to copper extraction of a mineral sulfide and a weathered ore from the Brazilian Amazon region. Samples (granulometry of 2.0/4.75 mm) were characterized by X-ray diffraction (XRD), energy dispersive X-ray fluorescence (EDXRF) spectrometry and scanning electrons microscopy (SEM). The pH and Oxidation-reduction potential (Eh) were daily monitored and leachate samples were collected for copper extraction determination by EDXRF. After 47 days, the columns bioleaching efficiency was 1% (1298 mg Cu·L−1) and 0.95% (985 mg Cu·L−1) for 2.00/4.75 mm sulfide ore, respectively, whereas the stirred reactors bioleaching resulted in 4% (348 mg Cu·L−1) for the mineral sulfide and 47% (295.5 mg Cu·L−1) for the weathered ore