Effect of organic and conventional farming on soil bacterial diversity of pecan tree (Carya illinoensis K. Kosh) orchard across two phenological stages.

We described the bacterial diversity of walnut grove soils under organic and conventional farming. The bacterial communities of rhizospheric and nonrhizospheric soils of pecan tree (Carya illinoensis K. Koch) were compared considering two phenological stages (sprouting and ripening). Sixteen operational taxonomic units (OTUs) were identified significantly more abundant according to the plant development, only one according to the farming condition, and none according to the soil origin. The OTUs specificaly abundant according to plant development included Actinobateria (2) and Betaproteobacteria (1) related OTUs more abundant at the sprouting stage, while at the fruit ripening (FR) stage the more abundant OTUs were related to Actinobacteria (6), Alphaproteobacteria (6), and unclassified Bacteria (1). The Gaiellaceae OTU18 (Actinobacteria) was more abundant under conventional farming. Thus, our study revealed that the plant development stage was the main factor shaping the bacterial community structure, while less influence was noticed for the farming condition. The bacterial communities exhibited specific metabolic capacities, a large range of carbon sources being used at the FR stage. The identified OTUs specifically more abundant represent indicators providing useful information on soil condition, potential tools for the management of soil bacterial communities.

Bioflotation of sulfide minerals with Acidithiobacillus ferrooxidans in relation to copper activation and surface oxidation.

Surface oxidation of sulfides and copper (Cu) activation are 2 of the main processes that determine the efficiency of flotation. The present study was developed with the intention to ascertain the role of the phenomena in the biomodification of sulfides by Acidithiobacillus ferrooxidans culture (cells and growth media) and their impact in bioflotation. Surface characteristics of chalcopyrite, sphalerite, and pyrrhotite, alone and in mixtures, after interaction with A. ferrooxidans were evaluated. Chalcopyrite floatability was increased substantially by biomodification, while bacteria depressed pyrrhotite floatability, favoring separation. The results showed that elemental sulfur concentration increased because of the oxidation generated by bacterial cells, the effect is intensified by the Fe(III) left in the culture and by galvanic contact. Acidithiobacillus ferrooxidans culture affects the Cu activation of sphalerite. The implications of elemental sulfur concentration and Cu activation of sphalerite are key factors that must be considered for the future development of sulfide bioflotation processes, since the depressive effect of cells could be counteracted by elemental sulfur generation.

An optical overview of poly[µ(2)-L-alanine-µ(3)-nitrato-sodium(I)] crystals.

Single crystals of the semiorganic materials, L-alanine sodium nitrate (LASN) and D-alanine sodium nitrate (DASN), were grown from an aqueous solution by slow-evaporation technique. X-ray diffraction (XRD) studies were carried for the doped grown crystals. The absorption of these grown crystals was analyzed using UV-Vis-NIR studies, and it was found that these crystals possess minimum absorption from 200 to 1100 nm. An infrared (FTIR) spectrum of single crystal has been measured in the 4000-400 cm(-1) range. The assignment of the observed vibrational modes to corresponding symmetry type has been performed. A thermogravimetric study was carried out to determine the thermal properties of the grown crystal. The efficiency of second harmonic generation was obtained by a variant of the Kurtz-Perry method.

Growth, yield, and nutrient status of pecans fertilized with biosolids and inoculated with rizosphere fungi.

The application of anaerobically digested biosolids as a nutrient source for pecan, Carya illinoinensis (Wangeh.) K. Koch, cultivar Western, was evaluated. Conventional NPK fertilizers (CF) and biosolids included a treatment with the rhizospheric fungi Pisolithus tinctorius+Scleroderma sp. and Trichoderma sp. After an average of three years, the tree trunks with biosolid treatment grew 9.5% more than with CF; the length of the bearing shoots was 18.1 and 18.3cm and the production of nuts/tree was 9.26 and 8.75kg for pecans with CF and with biosolids, respectively. Western foliar nutrient concentration and nut quality were statistically equal in trees with CF and with biosolids. Soil inoculation with mycorrhizal fungi improved shoot growth by 19.4% when CF was applied, but did not when biosolids were used. Nutrient status and yield did not increase with mycorrhizal fungi. The addition of Trichoderma sp. did not favor any of the variables evaluated with both nutrient sources. Biosolids are efficient fertilizer at promoting the growth, production and nut quality of pecan trees.

TEM evidence of ultrastructural alteration on Pseudomonas aeruginosa by photocatalytic TiO2 thin films.

The antibacterial efficiency of longwave UV-irradiated TiO(2) thin films as well as the ultrastructural damage on bacterial cells was evaluated using Pseudomonas aeruginosa as a model. The quantitative antibacterial efficiency assays showed a bacterial inhibition in the range of 32-72% at different times of irradiation. Transmission electron microscopy (TEM) was used to detect the effect of irradiation of TiO(2) thin films on the ultrastructure of the bacterial cell in order to reveal possible cellular damage. After 40 min irradiation, an abnormal cellular division was observed: instead of a normal septum, an 'elongated bridge' was formed. At a longer irradiation time, wavy structures all around the outer cell membrane were observed, and also some bubble-like protuberances, which expelled inner material. The mechanism of irreversible bacterial cell damage caused by the photocatalytic effect of TiO(2) could be related to abnormal cell division, aside from the reported physicochemical alteration of the cell membrane.

Photoinduced bactericidal activity against Pseudomonas aeruginosa by TiO(2) based thin films.

The photoinduced bactericidal capacity of TiO(2) based films was evaluated, using as model organism Pseudomonas aeruginosa. Thin films were obtained by spray pyrolysis; they included undoped, Cu doped, and Al doped TiO(2). Scanning electron microscopy was used to observe the final effect of the irradiated films upon the bacteria. Depending on the composition and characteristics of the films, quantitative experiments show that bacterial inhibition varies between 28 and 96%. The order of magnitude of the average quantum yield of the films was determined between 10(-9) and 10(-11) inhibited bacterial per photon.