Bioaccumulation of silver and the isolation of metal-binding protein from P.diminuta

• Main Authors: Zaharah Ibrahim, Wan Azlina Ahmad, Abu Bakar Baba
• Format: Article
• Language: English
• Published: Instituto de Tecnologia do Paraná (Tecpar) 2001-09-01
• Series: Brazilian Archives of Biology and Technology
• Subjects: Bioaccumulation; metal-binding proteins; Pseudomonas diminuta
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-89132001000300001
• ISSN: 1516-8913; 1678-4324

A silver uptake study by Pseudomonas diminuta was carried out by growing the bacteria in a chloride-free medium (CFM) containing silver ions (50 muM) in a batch culture. From the results, it was found that higher amounts of silver were accumulated inside the cell during early exponential phase compared to the amount bound at the cell surface. This suggested a possible mechanism for metal uptake during bacterial growth. In view of this, attempts were made to isolate proteins which might be associated with silver-binding properties from cultures of P.diminuta grown in the presence and absence of silver. The proteins were first extracted from the bacterial cultures by precipitation with ammonium sulfate followed by purification using isoelectric focussing and SDS-PAGE. Results of the experiment showed the presence of low molecular weight and high molecular weight proteins containing silver with pI values ranging from 2.0 to 9.0 for bacteria grown in the presence of silver.<br>Um estudo sobre o crescimento de Pseudomonas diminuta em um meio contendo cloreto livre (CFM) e íons de prata na concentração (50 µM) em uma cultura em batelada. Os resultados demonstraram que grandes quantidades de prata foram acumuladas dentro da célula durante a fase exponencial de crescimento comparada à uma quantidade limitada na superfície da célula. Isto sugeriu um mecanismo captação do metal durante o crescimento bacteriano. Em vista disto, tentativas foram realizadas no sentido de isolar as proteínas relacionadas com a propriedade de se ligar a prata em cultura P.diminuta em um meio contendo ou não íons prata. As proteínas foram extraídas das culturas bacterianas pela precipitação com o sulfato do amônio seguido de sua purificação utilizando um focalizador isoelétrico e SDS-PAGE. Os resultados desta experiência mostraram a presença de proteínas de alto e baixo peso molecular contendo prata com pI variando entre 2,0 a 9,0 quando as bactérias crescem na presença da prata.