Use of Polyguanidine-Derivatives-Based Biocides for Microbial Growth Inhibition and for the Development of a Novel Polyethylene-Based Composite Material Resistant to the Formation of Multispecies Microbial Biofilms

This study aimed to investigate the dependence of the biocidal activity of polyguanidine (co)polymers on their structure during the formation of biofilms by active PE-degrading cultures of model microorganisms. The Bc-2 copolymer of methacryloyl guanidine hydrochloride (MGHC) and diallyldimethylammonium chloride (DADMAC), which suppressed both the formation of biofilms and the growth of planktonic cultures, exhibited the highest activity. When PE was exposed in tropical soil, the composition of the microbial community on the PE surface differed significantly from that of the community in the surrounding soil. In particular, the proportion of Actinobacteria increased from 7% to 29%, while the proportion of Bacteroidetes decreased from 38% to 8%. Keywords: biofilms, polyhexamethylene guanidine salts, dynamics of biofilm formation, antibiofilm effect, composite materials

Caracterização da fauna edáfica na produção pecuária em distintos sistemas de pastoreio

Este trabalho teve o objetivo de avaliar a densidade e diversidade da faunaa edáfica em dois períodos do ano (inverno e primavera) em sistema de pastoreio contínuo racional Voisin (PRV), com três profundidades do solo. As avaliações foram realizadas conforme o método recomendado pelo programa “Tropical soil Biology and Fertility” (TSBF). A maior densidade da fauna edáfica foi identificada no PRV durante o período de primavera, apesar de termos uma densidade mais baixa de insetos comparado com o inverno. Foi observada a similaridade da fauna nas diferentes profundidades do solo, onde se observou que a profundidade de 0 a10 cm e muito similar à de 10 a 20 cm em o tratamento com exceção do período de PRV inverno, onde a fauna encontrada na cobertura e nos estratos de 0 a 10cm são mais semelhantes considerando a diversidade. Não foi encontrada diferença significativa enquanto a função biológica da fauna edáfica e o tipo de manejo de pastoreio ou a estação do ano que foram coletadas as amostras. O maior número de indivíduos por família maior foi encontrado no manejo PRV durante a estação de inverno, no entanto a diversidade entre estes indivíduos foi mais baixa que nos demais tratamentos.

Phosphate fertilization regulates arbuscular mycorrhizal symbiosis in roots of soybean (Glycine max L.) cultivars in a humid tropical soil

<p>The effect of phosphate fertilization on arbuscular mycorhizal symbiosis and grain yields of soybean cultivars was investigated on P deficient soil. A two-year field study (2017-2018) consisting of two soybean cultivars (TGx 1448-2E and TGx 1440-1E) and three phosphate rates [0, 20 and 40 kg P₂O₅ ha^-1) was laid out in a randomized complete block design with three replications. The results showed that P fertilization significantly (<em>p</em> &lt; 0.001) reduced AMF root colonization of both cultivars in the two cropping years. The arbuscular, vesicular, internal hyphae and total colonization in the root cortex of the soybean cultivars were significantly (<em>p</em> &lt; 0.001) reduced with high P (40 kg) application. However, moderate P (20 kg) promote AMF symbiosis in roots of ‘TG x 1448-2E‘. Dry mass (root and shoot), P uptake and grain yield of the soybean cultivars were significantly (<em>p</em> &lt; 0.001) increased with increasing P ferilization. There was a strong linear relationships between root colonization and total dry matter mass (r = 0.81), P uptake (r = 0.81) and grain yield (r = 0.85). Thus, it could be concluded that moderate P fertilizer application is needed to promote mycorrhizal symbiosis in soybean and sustainable crop production in humid tropical soil.</p>

The Residual Copper and Zinc in Tropical Soil over 21 Years after Amendment with Heavy Metal Containing Waste, Lime, and Compost

This research aimed to evaluate the residual Cu and Zn in tropical soil over 21 years after amendment with industrial waste, lime, and compost. Soil samples were collected from a well-maintained experimental field amended one time with industrial waste high in Cu and Zn set in 1998 at about 1.5–20 years after amendment. Treatments were arranged in a randomized block design with a metal-wares industrial waste at rates 0, 15, and 60 Mg·ha−1, lime at 0 and 5 Mg·ha−1, and compost at 0 and 5 Mg·ha−1. Soil samples were also taken vertically in the exact plot centers at depths of 0–75 cm of plots not amended with lime and compost and also from topsoils (0–15 cm) at 90 points with distances 50 cm between each other in each of the respective plots 21 years after amendment. Significant increases in Cu and Zn caused by waste were observed over 21 years. The increase in soil pH by lime was observed over 10 years but its effect in decreasing Cu and Zn was observed only at 1.5 years, particularly in topsoils. However, the effect of lime in lowering Cu and Zn was observed over 20 years when waste and/or compost were also given. Similarly, the effect of compost was absent over 20 years but significant when waste and/or lime were also given. The relative concentration of Cu and Zn in the 60 Mg waste ha−1 plots decreased over 20 years to 17–53% for Cu and to 12–33% for Zn; their concentrations were, in general, lower with lime and/or compost addition. The relative concentrations of Cu and Zn significantly decreased over 21 years in plots with 15 or 60 Mg·ha−1 and increased in the control plots. Heavy metals moved in soil significantly through soil tillage and erosion and partially by leaching.