Isolation And Identification Of Acidophilic Heterotrophic Bacteria And Their Ecological Effects In Bioleaching

Microbial life in extremely low pH(<3)natureal and man-made environments may be considerably diverse. Prokaryotic acidophiles(eubacteria and archaea) have been the focus of much of the research activity in this area, primarily because of the importance of these microorganisms in biotechnology and in environmental pollution(genesis of "acid mine drainage"). Exploitation of acidophilic microorganisms for the processing of ores of gold, copper and other metals(biomining) has developed into one of the major areas of biotechnology. On the other hand, the same microorganisms are responsible for generating acidic metalliferous wastes, which cause widespread environmental pollution. Clearly there is a need to harness the positive aspects of these microorganisms to accentuate the net benefits they can deliver while at the same time limiting their deleterious effects. To achieve this goal, it will be necessary to extend our understanding of fundamental as well as applied aspects of acidophilic microbiology.In this report, three strains of heterotrophic acidopilies were isolated from different copper mining areas in China( Shanxi and Jiangxi). They were studied in phenotypic characteristics , physiological properties and phylogenetic relationships and were maintained in 30% glycerol. By the research of morphology, the three strains of heterotrophic acidopilies were all Gram-negative, rods, motile, no spore. They were mesophiles, optimum growth temperature was30℃～35℃, and optimum pH were 3.0～3.5. They cannot use ferrous iron and elemental sulfur as the sole energy source. Therefore, the three isolates were acidophilic chemoorganotrophic bacteria.By the analysis of 16s rRNA gene, LY-1, DX-4 can best be allocated to the gcnus Acidiphilium, and YP-6 to the genus Pseudomonas. LY-1 and DX-4 had high similarity, but they should be placed in separate species of the genus.The stimulating effect of heterotrophic acidophilies was investigated on the growth and on the ferrous iron oxidation of At.ferrooxidans in synthetic media, in order to study the ecological effects of heterotrophic acidopilies in bioleaching. The data indicated that the three strains of heterotrophic acidopilies can promote the growth of autotrophic bacteria on different level. Also, they can reduce Fe³⁺ , according to the rate of reducing, LY-1>DX-4>YP-6.