Abstract In view of the complexity of the processes associated to water quality, this study objective is to identify the main factors related to spatial and seasonal variability in water courses of the Lobo Stream River Basin. To this, multivariate statistical techniques were used. Data collection for water quality and streamflow variables were carried out monthly, from May 2018 to April 2019, at 10 monitoring points along basin’s tributaries. The results show that, during the dry season, the main causes for water quality decrease are related to erosion process on the river margins, which is intensified by inadequate handling in livestock activities in some monitoring points. In the rainy season, the main causes are related to soil leaching in agricultural areas that increases the nitrogen compounds concentration and reduces water quality. However, in addition to this, it was noted that regardless the environmental conditions, the most impactful factor is the point pollution from the effluent discharge of Itirapina City sewage treatment plant, responsible for nutrient concentration increase, organic contamination, OD reduction, and, consequently, water quality deterioration. With this, the study shows how multivariate statistical analysis enables more relevant evaluation of water quality data variability and supports further studies in the basin.

The investigations of the antibacterial actions, observed in ternary associations involving silver nanoparticles (AgNPs), chitosan and the antibiotics azithromycin (AZ), levofloxacin (LE) or tetracycline (TE), against Gram-negative and Gram-positive bacterial strains, were performed by in vitro antimicrobial susceptibility testing and checkerboard assays. The pH impact in the culture medium was carefully discarded, but preserving the best conditions for solubilizing chitosan. The synergistic antibacterial effects were observed in the most combinations of AgNPs, chitosan and antibiotic, leading to a reduction from 37 to 97% in the minimum inhibitory concentration of the drugs. The mechanisms for the enhanced antimicrobial effects were proposed based on the investigations of the adsorptions of the drugs on the silver surfaces through surface-enhanced Raman scattering (SERS) spectroscopy.

Para avaliar o desempenho agronómico e a composição química dos grãos de milho provenientes de plantas submetidas à inoculação das sementes com Pseudomonas fluorescens e cultivadas com diferentes doses de adubação fosfatada, conduziu-se um estudo avaliando dez tratamentos, sob o delineamento experimental inteiramente casualizado, em esquema fatorial 5 x 2, sendo cinco doses de adubação fosfatada (0, 40, 80, 100 e 160 kg ha-1de P2O5), combinadas com dois níveis de inoculação (presença e ausência), com oito repetições. Foram avaliadas características fitométricas, componentes de produção, produtividade e a composição química das cariopses. Os dados foram submetidos à análise de variância complementada pelo teste de Tukey p<0,05 e estudo de regressão para efeito de doses. A inoculação com P. fluorescens associada a adubação fosfatada nas doses de 80 e 160 kg ha-1 de P2O5 favorece a massa de matéria seca de raiz. O desempenho agronómico da cultura, os teores de nutrientes e proteína nas cariopses de milho não foram influenciados pela inoculação com P. fluorescens e adubação fosfatada, demonstrando a necessidade de seleção de estirpes que estabeleçam relações mais satisfatórias e estáveis com a planta hospedeira, bem como a identificação de condições ambientais que favoreçam a interação entre planta e bactéria.

To evaluate the agronomic performance and chemical composition of corn grains of plants inoculated with Pseudomonas fluorescens and cultured with different doses of fertilization, an experiment was conducted with ten treatments under the completely randomized design in a 5 x 2 factorial arrangement with five levels of phosphate fertilizer (0, 40, 80, 100 and 160 kg ha-1) combined with two levels of inoculation (with and without) with four replications. Fitometrics characteristics, yield components, productivity and chemical composition of the grains were evaluated. The data were submitted to ANOVA complemented by p<0.05 Tukey test and regression study for the effect of doses of phosphate fertilizer. The inoculation with P. fluorescens associated with phosphorus fertilization at doses of 80 and 160 kg ha-1 of P2O5 favored the mass of dry root. The agronomic performance, the levels of nutrients and protein in maize grain were not influenced by inoculation with P. fluorescens and phosphorus fertilization, demonstrating the need for selection of strains that establish relations more satisfactory and stable with the host plant, as well as the identification of environmental conditions that favor the interaction between plant and bacteria.