16S rDNA USES TO IDENTIFY AND QUANTIFY BACTERIA IN THE BIOLEACHING PROCESS

摘要

Identification and quantification of bacteria in bio-leaching solutions, has been traditionally realized by means of culture techniques which do not easily permit to differentiate between the most important strains of ferrous iron oxidizing bacteria like Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans and Sulfobacillus thermosulfido-oxidans and sulfur oxidizing bacteria like Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans or Sulfobadllus thermosulfidooxidans. The molecular technique, actually in full development, permit rapid identification and in some cases also the quantification of the bacterial population, without a period of culture. These techniques are based in the amplification by means of PCR (polymerase chain reaction) of a segment of DNA, the 16S rDNA, which is present in all cells and is specific for each bacterial strain. In this work we present an application of the PCR technique to the study of microbial diversity present in 10 solutions coming from a leaching process in column of a mineral sulphide with a high concentration of chalcopyrite. With this purpose specific primers for the amplification of the 16S rDNA segment of each microbial strain above mentioned were designed and synthetised to be used in its detection in the extracted DNA from the cells present in the solution. When a determined strain gave positive to the detection, the quantitative NMP-PCR test was applied. A. ferrooxidans was detected and quantified in all samples (10), A. thiooxidans and 5. thermosulfldooxidans were detected and quantified in 7 of the 10 samples. L. ferrooxidans was not detected in any sample. The implemented techniques is highly specific and less laborious, compared with the culture techniques usually used and permit the detection of bacteria at concentrations as low as 1.0 x 10~6 bacterias/cm~3.