Microwave assisted biocidal extraction is an alternative method to measure microbial biomass of carbon from cultivated and non-cultivated soils.

Developing simple and cost-effective methods for soil microbial biomass carbon (MBC) measurement eases routine laboratory analysis and enables large numbers of soil samples to be measured in a relatively short period of time. Thus, the objective of this study was to develop a microwave-assisted biocidal-extraction (MWE) method which does not employ CHCl3 as biocide and K2SO4 as C-extractor, to estimate MBC. First, the microorganisms of soil samples are killed using microwave (MW) irradiation at energy level of 800 J g-1 soil as biocide followed by microwave irradiation extraction (MWE) at 562 W (120 J g-1 soil for 1 min), using deionized water as solvent. Microbial biomass of carbon from two contrasting soils microwaved with 80, 100, and 140 J g-1 soil did not differ from those obtained by using the chloroform fumigation-extraction (CFE) method with 0.5 mol L-1 K2SO4 as extractant. To evaluate the robustness of the MWE method, twenty-six soil samples, from cultivated and non-cultivated areas, with clay contents from 70-690 g kg-1, organic carbon from 5.52 to 50.82 g C kg-1 and pH values from 3.9 to 6.8 were analyzed for MBC using MWE and CFE methods. There was a linear regression (MW = - 17.87 + 0.92*K2SO4; R2 = 0.705; p < 0.001) between MWE and CFE. The biocidal microwave-assisted extraction method using 120 J g-1 soil for 1 min is a cleaner method for evaluating MBC, because it does not require chloroform, potassium sulfate salt and takes a shorter time to extract a set of soil samples.

Composition of bacterial community in enrichment cultures of shale by-products from Irati Formation, Brazil

ABSTRACT We examined microbial communities from enriched fine and retorted shale particles using sequencing of V4 variable region of 16S rRNA. High number of microbial genera was found in both enriched shale by-products that were dominate by Actinobacteria, Firmicutes and Proteobacteria, showing differences due to microbial colonization after the pyrolysis process.

Composition of bacterial community in enrichment cultures of shale by-products from Irati Formation, Brazil.

We examined microbial communities from enriched fine and retorted shale particles using sequencing of V4 variable region of 16S rRNA. High number of microbial genera was found in both enriched shale by-products that were dominate by Actinobacteria, Firmicutes and Proteobacteria, showing differences due to microbial colonization after the pyrolysis process.

Talaromyces sayulitensis, Acidiella bohemica and Penicillium citrinum in Brazilian oil shale by-products.

Fine shale particles and retorted shale are waste products generated during the oil shale retorting process. These by-products are small fragments of mined shale rock, are high in silicon and also contain organic matter, micronutrients, hydrocarbons and other elements. The aims of this study were to isolate and to evaluate fungal diversity present in fine shale particles and retorted shale samples collected at the Schist Industrialization Business Unit (Six)-Petrobras in São Mateus do Sul, State of Paraná, Brazil. Combining morphology and internal transcribed spacer (ITS) sequence, a total of seven fungal genera were identified, including Acidiella, Aspergillus, Cladosporium, Ochroconis, Penicillium, Talaromyces and Trichoderma. Acidiella was the most predominant genus found in the samples of fine shale particles, which are a highly acidic substrate (pH 2.4-3.6), while Talaromyces was the main genus in retorted shale (pH 5.20-6.20). Talaromyces sayulitensis was the species most frequently found in retorted shale, and Acidiella bohemica in fine shale particles. The presence of T. sayulitensis, T. diversus and T. stolli in oil shale is described herein for the first time. In conclusion, we have described for the first time a snapshot of the diversity of filamentous fungi colonizing solid oil shale by-products from the Irati Formation in Brazil.

Application of Landfill Leachate Improves Wheat Nutrition and Yield but Has Minor Effects on Soil Properties.

Landfill leachates, which are potential pollutants, may also carry significant amounts of nutrients that can be recycled by plants. We assessed the nutritional status and yield of wheat ( L.) and properties of a Rhodic Kandiudult soil (depths of 0-10, 10-20, 20-40, and 40-60 cm) after 11 applications of landfill leachate over 4 yr. In the last application, wheat received 0, 32.7, 65.4, 98.1, or 130.8 m ha (875 mg L of nitrogen, N) of leachate and a positive control (90 kg ha of N as urea) 15 d after sowing. Urea increased nitrate (>160 mg kg) in the topsoil (down to 40 cm), whereas landfill leachate increased nitrate (>60 mg kg) only at 40 to 60 cm with the highest dose, suggesting leaching. Urea-treated soil had less negative ΔpH, which might have led to greater retention of nitrate in the topsoil. Sodium (0.02-0.26 cmol Na kg), potassium (0.18-0.82 cmol K kg), and electrical conductivity (0.05-0.14 dS m) all increased with leachate dosage. Treatments did not affect resistance to penetration and clay dispersion. Basal respiration increased with leachate dosage, whereas dehydrogenase activity decreased, suggesting effects on soil microbial metabolism. Microbial biomass and soil enzyme activities were not affected by addition of leachate. Nitrogen nutrition (15.1-22.7 g N kg in flag leaves) and grain yield (1381-2378 kg grain ha) increased with leachate dosage so that the highest dose gave results similar to those for urea-treated plants (2563 kg grain ha). Landfill leachate showed strong potential as source of N for wheat but caused none, or transient, effects on soil properties. However, nitrate from leachate was more leachable than nitrate from urea.

Effect of Landfill Leachate on Cereal Nutrition and Productivity and on Soil Properties.

Landfill leachates carry nutrients, especially N and K, which can be recycled in cropping systems. We applied doses of landfill leachate (0 [Control], 32.7, 65.4, 98.1, and 130.8 m ha) three times in 2008 and three times in 2009 on a clay Rhodic Kandiudult soil. In 2009, black oat ( L.) and corn ( L.) were cropped in succession and assessed for concentration of nutrients in leaves and for shoot biomass and grain yield, respectively. As a positive control, an additional treatment with urea (120 kg ha of N) was studied in corn. Soil was sampled at four depths (down to 60 cm) in three sampling dates to assess chemical and biochemical properties. Concentration of nutrients in leaves, oat biomass (8530-23,240 kg ha), and corn grain yield (4703-8807 kg ha) increased with increasing doses of leachate. There was a transient increase in the concentration of nitrate in soil (3-30 mg kg), increasing the risk of N losses by leaching at doses above 120 kg ha N, as revealed by an estimated N balance in the cropping system. Sodium and K in soil also increased with increasing doses of leachate but decreased as rainfall occurred. The activity of dehydrogenase decreased about 30% from the control to the highest dose of leachate and urea, suggesting an inhibitory effect of mineral N on microbial metabolism. Landfill leachate was promising as a source of N and K for crop productivity and caused minor or transient effects on soil properties.

Polyphasic approach for the characterization of rhizobial symbionts effective in fixing N(2) with common bean (Phaseolus vulgaris L.).

Common bean (Phaseolus vulgaris L.) is a legume that has been reported as highly promiscuous in nodulating with a variety of rhizobial strains, often with low effectiveness in fixing nitrogen. The aim of this work was to assess the symbiotic efficiency of rhizobial strains isolated from common bean seeds, nodules of Arachis hypogaea, Mucuna pruriens, and soils from various Brazilian agroecosystems, followed by the characterization of elite strains identified in the first screening. Forty-five elite strains were analyzed for symbiotic properties (nodulation, plant-growth, and nitrogen-fixation parameters) under greenhouse conditions in pots containing non-sterile soil, and variation in symbiotic performance was observed. Elite strains were also characterized in relation to morpho-physiological properties, genetic profiles of rep-polymerase chain reaction (PCR; BOX), and restriction fragment length polymorphism (RFLP)-PCR of the 16S rRNA. Sequence analyses of the 16S rRNA were obtained for 17 strains representative of the main groups resulting from all previous analyses. One of the most effective strains, IPR-Pv 2604, was clustered with Rhizobium tropici, whereas strain IPR-Pv 583, showing lower effectiveness in fixing N(2), was clustered with Herbaspirillum lusitanum. Surprisingly, effective strains were clustered with unusual symbiotic genera/species, including Leifsonia xyli, Stenotrophomonas maltophilia, Burkholderia, and Enterobacter. Some strains recognized in this study were outstanding in their nitrogen-fixing capacity and therefore, show high biotechnological potential for use in commercial inoculants.