RESUMO
In this study, the biosorption ability of various potentially toxic elements from phosphate-processing effluent (PPE) using the indigenous bacterium Serratia rubidaea NCTC12971 immobilized in Ca-alginate beads was investigated. The experimental data analyzed by the Langmuir isotherm revealed that the optimum dose of 2 g·100 ml−1 of immobilized S. rubidaea NCTC12971 at pH 7 and a contact time of 48 h allowed the removal of 92.07%, 98.05%, 95.57%, and 88.39% of lead (Pb (II)), cadmium (Cd (II)), copper (Cu (II)), and zinc (Zn (II)), respectively. Moreover, under the Langmuir isotherm, the maximum single-layer adsorption capacity (qmax) of the biosorbent was estimated to 32.14 mg g−1, 45.87 mg g−1, 0.06 mg g−1, and 3.01 mg g−1 for Pb (II), Cd (II), Cu (II), and Zn (II), respectively, under the stated conditions. Alternatively, the regeneration and reuse of the Ca-alginate beads was evaluated. Indeed, after four consecutive adsorptiondesorption cycles, there was no significant loss in the biosorption capacity. The effectiveness of the bacterial biosorption as treatment process was evaluated by assessing the phytotoxicity of the treated effluent (TE) on Medicago sativa and Lactuca sativa seed germination and their root elongation. Results exhibited a significant toxicity removal expressed by a notable increase in the germination indices (GI), which reach 80% and 70%, respectively, for Medicago sativa and Lactuca sativa compared to the GI values of 46.6% and 16.6% of the same species in presence of the untreated effluent (PPE).(AU)
Assuntos
Serratia , Alginatos , Adsorção , Esgotos , Microbiologia da Água , Medidas de Toxicidade , Germinação , Medicago sativa , Lactuca , MicrobiologiaRESUMO
Uncontrolled waste disposal has continuously threatened the health of the surrounding environment through the leaching of hazardous xenobiotics. Systemic toxicity and genotoxicity potential of waste leachates from Onitsha municipal dumpsite were investigated in giant African land snail (Limicolaria aurora) through oxidative stress biomarker and micronucleus test assessment respectively. Physicochemical indices were evaluated in the leachate following standard protocols. Snails were exposed to different concentrations (0, 6.25, 12.5, 25.0 and 50.0%) of waste leachate for 21 days; oxidative stress biomarkers and micronucleus analysis performed on snail digestive gland and hemocyte respectively. The leachate induced dose-duration dependent increase (P< 0.05) in Superoxide dismutase, Catalase, malondialdehyde and Glutathione peroxidase levels with associated decrease in total protein concentrations in the exposed snails compared to the control. Similarly, the frequency of micronucleus and other nuclear abnormalities shows concentration dependent increase (P< 0.05) in treated groups. This observed genotoxic effect might be induced by the oxidative stress, via the production of reactive oxygen species. This shows that waste leachate contains hazardous and genotoxic compounds capable of inducing oxidative stress and DNA damage. Therefore, continuous exposure of waste leachate into the environment could pose a grave health risk to the surrounding biota, humans included
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Assuntos
Animais , Estresse Oxidativo/genética , Esgotos , Eliminação de Resíduos Líquidos , Caramujos/genética , Micronúcleo Germinativo/genética , Monitoramento Ambiental/métodos , 34709RESUMO
A study on the distribution patterns of enteropathogenic bacteria polluting the shoreline in Natal, Rio Grande do Norte, Brazil, was carried out based on 72 samples obtained from three storm sewers and adjoining beach locations, Praia do Meio (PM), Areia Preta (AP) and Ponta Negra (PN). From each location, 12 water samples were taken and analyzed for fecal coliforms (FC) and Escherichia coli. In AP, two (16.7%) of the seawater samples and five (41.7%) of the storm sewer samples yielded values above 1.1 x 107 FC/100 ml, whereas only one (8.3%) of the samples from PM reached this level. There was no correlation (p > 0.05) between rainfall indices and FC values. A total of 64 E. coli isolates were obtained: 37 from the storm sewer samples and 27 from the seawater samples. Of these isolates, four (O143, two O112ac, and O124) were enteroinvasive and two (O111 and O125) were enteropathogenic. Resistance to antibiotics and to heavy metals was also analyzed. Almost 36% of the E. coli strains isolated were resistant to more than one antibiotic. All strains were resistant to zinc and copper at the highest concentration tested (250 microg/ml), and several (23.4%) were resistant to mercury at 50 microg/ml. Our results agreed with previous reports that antibiotic resistance is commonly associated with heavy-metal resistance in pathogens (AU)
Se realizó un estudio sobre la distribución de las bacterias enteropatógenas que contaminan la costa en Natal (Rio Grande do Norte, Brasil), a partir de 72 muestras obtenidas en tres colectores pluviales (storm sewers) y en unas playas adyacentes a los mismos, Praia do Meio (PM), Areia Preta (AP) y Ponta Negra (PN). En cada punto se tomaron 12 muestras, que se analizaron en busca de coliformes fecales (CF) y de Escherichia coli. En AP, dos (16,7%) de las muestras de agua de mar y cinco (41,7%) de las de agua del colector dieron valores superiores a 1,1 × 107 CF/100 ml, mientras que sólo una (8,3%) de las muestras de PM alcanzó este nivel. No se encontró correlación (p > 0,05) entre los índices de pluviosidad y los valores de CF. Se obtuvo un total de 64 aislados de E. coli: 37 a partir de muestras de colectores y 27 a partir de muestras de agua de mar. De estos aislados, cuatro (un O143, dos O112ac y un O124) eran enteroinvasivos y dos (O111 y O125) eran enteropatógenos. Se analizó también la resistencia a antibióticos y a metales pesados. Casi el 36% de las cepas de E. coli aisladas eran resistentes a más de un antibiótico. Todas las cepas eran resistentes al zinc y al cobre a la mayor concentración probada (250 µg/ml), y varias cepas (23.4%) eran resistentes al mercurio a 50 µg/ml. Nuestros resultados coinciden con trabajos anteriores que indican que en bacterias patógenas la resistencia a antibióticos suele ir asociada a la resistencia a metales pesados (AU)