Adaptive and cross-protective responses against cadmium and zinc toxicity in cadmium-resistant bacterium isolated from a zinc mine

Cadmium (Cd) is a major environmental hazard, which usually is detected in its ionic form of Cd2+. It also causes adverse toxic effects on human health and other living organisms. Cd-resistant bacteria were isolated from Cd-contaminated soils. One isolate, TAK1, was highly resistance level to Cd toxicity. TAK1 was isolated from soil contaminated with a high Cd concentration (204.1 mg.kg-1). The result of 16S rDNA sequence analysis found that the TAK1 showed the similarity to Ralstonia sp. Physiological adaptive and cross-protective responses to Cd and Zn killing were investigated in Ralstonia sp.TAK1. Exposure to a low concentration of Cd induced adaptive resistance to higher concentrations of Cd. In addition, pretreatment of Ralstonia sp.TAK1 with an inducing concentration of Cd conferred cross-protective response against subsequent exposure to the lethal concentrations of Zn. The induced adaptive and cross-protective response Ralstonia sp.TAK1 required newly synthesized protein(s). Cd-induced adaptive and cross-protective responses against Cd and Zn toxicity are the important mechanisms used by Ralstonia sp.TAK1 to survive in the heavy metal contaminated environments. These findings might lead to the use of Ralstonia sp.TAK1 for microbial based remediation in Cd and Zn-contaminated soils.

Uso de cádmio metálico nas determinações espectrofotométricas de nitrato para sais de cura / Use of metallic cadmium in the determinations spectrophotometric of nitrate for curing salts

O experimento desenvolveu-se nos laboratórios de Química Analítica e do CEAQUIM (Centro de Apoio Químico) do Departamento de Química e Bioquímica – Instituto de Biociências – Campus de Botucatu – SP, com o objetivo de estudar o método espectrofotométrico de nitrato usando cádmio metálico para análises de sais de cura. Foram estudados influência do tempo de agitação, influência da massa de cádmio metálico, velocidade da agitação, e a influência de cloretos na redução do nitrato pelo cádmio metálico. Os testes estatísticos demonstraram que os melhores tempos de agitação, massas de cádmio metálico, velocidades de agitação foram a partir de 15 min, a partir de 10 g e 200 rpm, respectivamente. A presença de cloretos não inibiu a redução de nitrato.

Accumulation of cadmium from moderately concentrated cadmium solutions by chlorella and scenedesmus strains

A acumulaçäo de Cadmio a partir de soluçöes contaminadas com o metal foi estudada através do emprego de 3 diferentes microalgas. Dentre as espécies testadas a Chlorella homosphaera mostrou maior poder de acumulaçäo comparada com células de Scenedesmus quadricauda e Chlorella homosphaera e Scenedesmus quadricauda foram consideravelmente afetadas pela presen