BACTÉRIAS E BIOINDICADORES DE QUALIDADE DE ÁGUAS DE ECOSSISTEMAS ORIZÍCOLAS DA REGIÃO SUL DO BRASIL

The presence of heterotrophic bacteria in aquatic environments, such as those in the agricultural systems of irrigated rice fields, is determined by biotic and abiotic processes, with the focus on physical-chemical factors and highly complex interactions with other organisms. In this study, we address aspects related to these bacteria, such as:  bacterial diversity in rice growing areas, total coliforms and thermotolerant as environmental indicators.  Are also mentioned topics related to natural and artificial wetlands, the viability of enteric bacteria, the environmental impacts, reuse and monitoring of water in rice fields ecosystems.La presencia de bacterias heterotróficas en ambientes acuáticos, como los agroecosistemas de producción de arroz irrigado, esta determinada por procesos bióticos y abióticos, en los que destacan factores fisico-químicos e interacciones muy complejas con otros organismos. En este trabajo se discuten algunos aspectos relacionados a estas bacterias, como la diversidad bacteriana en zonas de cultivo de arroz y  coliformes totales y termotolerantes considerados como indicadores ambientales. También se discuten tópicos relacionados a humedales naturales y artificiales, a la viabilidad de bacterias entéricas, a los impactos causados y  a la reutilización y monitoreo del agua en los ecosistemas de cultivo de arroz.A presença de bactérias heterotróficas em ambientes aquáticos, como os agroecossistemas de produção de arroz irrigado, é determinada por processos bióticos e abióticos, onde se destacam os fatores físico-químicos e as interações de elevada complexidade com outros organismos. Nesse trabalho são abordados aspectos relacionados a estas bactérias, tais como: diversidade bacteriana em áreas orizícolas, coliformes totais e termotolerantes como indicadores ambientais. Também são mencionados tópicos relacionados aos wetlands naturais e artificiais, a viabilidade de bactérias entéricas, os impactos, a reutilização e o monitoramento da água nos ecossistemas orizícolas.

Bacterial Community of the Rice Floodwater Using Cultivation-Independent Approaches

In agricultural systems, interactions between plants and microorganisms are important to maintaining production and profitability. In this study, bacterial communities in floodwaters of rice fields were monitored during the vegetative and reproductive stages of rice plant development using 16S amplicon sequencing. The study was conducted in the south of Brazil, during the crop years 2011/12 and 2012/13. Comparative analyses showed strong differences between the communities of floodwaters associated with the two developmental stages. During the vegetative stage, 1551 operational taxonomic units (OTUs) were detected, while less than half that number (603) were identified in the reproductive stage. The higher bacterial richness observed in floodwater collected during the vegetative stage may have been favored by the higher concentration of nutrients, such as potassium, due to rhizodeposition and fertilizer application. Eighteen bacterial phyla were identified in both samples. Both communities were dominated by Gammaproteobacteria. In the vegetative stage, Alphaproteobacteria and Betaproteobacteria were more abundant and, in contrast, Bacilli and Clostridia were the more dominant classes in the reproductive stage. The major bacterial taxa identified have been previously identified as important colonizers of rice fields. The richness and composition of bacterial communities over cultivation time may contribute to the sustainability of the crop

Antimicrobial performance of thermoplastic elastomers containing zinc pyrithione and silver nanoparticles

The purpose of the present study was to evaluate the antimicrobial potential of styrene-ethylene/ butylene-styrene based thermoplastic elastomers (TPE) incorporated with zinc pyrithione (ZnPT) and silver nanoparticles (AgNano). Japan Industrial Standard was applied to evaluate the antimicrobial potential of incorporated TPE compounds against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Antifungal action was evaluated against Aspergillus niger, Candida albicans and Cladosporium cladosporioides. Samples prepared with ZnPT eliminated 99.9% of the E. coli and 99.7 % of the S. aureus population, and presented an inhibition zone in the fungal assay. Samples prepared with AgNano eliminated 99.7% of the E. coli and 95.5 % of the S. aureus population. There was no inhibition zone in samples containing AgNano; however, these samples did not present fungal growth on their surfaces. TPE samples containing ZnPT showed biocidal activity against the microorganisms tested and can be used to develop antimicrobial products

Evaluation of the Toxicity of Silver/Silica and Titanium Dioxide Particles in Mammalian Cells

ABSTRACT The increasing concern over the spread of diseases has lead to a high consumption of antimicrobial additives in the medical and industrial fields. Since these particles can lixiviate from loaded materials, the contact between this additive and mammalian cells can occur during manufacture, use and disposal of the products. Silver on fumed silica (AgNP_SiO2) and titanium dioxide (TiO2) can be used as antimicrobial additives that are applied in polymeric formulation. While these additives can inhibit bacteria, fungus and virus proliferation; they may also be harmful to humans. Standard toxicological studies were undertaken using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide), CBPI (cytokinesis-block proliferation index) and micronucleus assay using different sets of additive concentrations. The nanosize of the samples evaluated was confirmed by transmission electronic microscopy. No significant micronucleus frequency increase or cell viability reduction were observed with the exposure of L-929 murine fibroblast cells to AgNP_SiO2 and TiO2 particles at any of the tested concentrations. The non toxic effect of the analyzed particles can be explained by considering its agglomeration tendency, composition, and crystalline form. Further investigations should be done to understand the interference of agglomeration and how it affects the toxicological study

Thermoplastic Elastomers Containing Zinc Oxide as Antimicrobial Additive Under Thermal Accelerated Ageing

<div><p>Styrene-ethylene/butylene-styrene (SEBS) copolymer- based thermoplastic elastomers (TPE) are applied in the production of household items used in places with conditions for microbial development. Metal oxides like zinc oxide (ZnO) and others can be added to the TPE composition to prevent microbial growth. The aim of this study is to evaluate the effect of thermal accelerated ageing on mechanical, chemical and antibacterial properties of SEBS-based TPE containing 0%, 1%, 3%, and 5% zinc oxide. Zinc oxide was characterized by laser diffraction, X-ray diffraction, superficial area, porosity and scanning electron microscopy. Both aged and unaged samples were analyzed by infrared spectroscopy, tensile at rupture, elongation at rupture, hardness and antimicrobial activity against Escherichia coli and Staphylococcus aureus. Following thermal exposure, a reduction of antimicrobial activity was observed. No significant difference was observed in the chemical and mechanical characteristics between aged and unaged samples.</p></div