Identificação e caracterização de genes expressos diferencialmente em Acidithiobacillus ferrooxidans na presença de sulfetos metalicos / Identification and characterization of differentially expression genes in Acidithiobacillus ferrooxidans in the presence of metal sulfides

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Acidithiobacillus ferrooxidans is a Gram-negative, mesophilic, acidophilic, chemolithoautotrophic bacterium that obtains energy from the oxidation of ferrous iron, elemental sulfur and reduced sulfur compounds. A. ferrooxidans is one of the most used microorganisms in bioleaching, an industrial process used for the recovery of copper, uranium or gold, fiom lowgrade ores. In the first part of this project the differentially expressed cDNAs were isolated by RAP-PCR from A. ferrooxidans cells maintained for 24 hours in the presence of the metal sulfides bomite and chalcopyrite. A total of 18 differentially expressed cDNAs were isolated. The differential expression of the cDNAs was confirmed by real time PCR. The results showed that these genes were not down-regulated in the presence of bomite and among the up-regulated genes were those involved in protein synthesis. In the presence of cha1copyrite, five genes related to p~otein processing ~ere down-regulated, and another five genes related to transport were upregulated. The up- and down-regulation of genes in the presence of bomite and chalcopyrite could be due to alterations in the ideal pH, the presence of copper ions in solution and nutrient limitation. Among the genes that were up-regulated in the presence of chalcopyrite, was one that encodes for a TonB-dependent receptor. This protein is part of a system involved in Fe3+ uptake. An analysis of the A. ferrooxidans genome was performed in the second part of this work and showed that the gene that encodes for !he TonB-dependent receptor is clustered with six other genes fiom the Fe3+ uptake system. The relative expression pattem of lliese genes was investigated by real time PCR in A. ferrooxidans cells maintained for 24 h iri, the presence of bomite and chalcopyrite. The results.showed that the expression of the genes is up-regulated in the presence of chalcopyrite and unchanged in the presence of bomite. A possible explanation for this is the amount of iron in solution that was smaller in the presence of chalcopyrite, since this copper sulfide is very refractory. The iron uptake genes are regulated by a protein named Fur. A bioinformatics analysis of the genomic region where these genes were found revealed the existence of three new Fur boxes. An analysis on the Conserved Domain Database (CDD NCBI) revealed that the TonB-dependent receptor belongs to the CirA family of receptors.

ASSUNTO(S)

reação em cadeia de polimerase polymerase chain reaction gene expression sulphides acidithiobacillus ferrooxidans sulfetos - metalurgia expressão genica

ACESSO AO ARTIGO

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