Molecular Biological Approach to Strain Improvement of 'Thiobacillus ferrooxidans' for Enhanced Metal Leaching Capabilities

摘要

The blue copper protein, rusticyanin, is thought to be the initial acceptor of electrons from Fe(2+). The ability to genetically clone and manipulate the gene for the protein would be a valuable approach to strain improvement. A necessary pre-requisite for cloning is to determine the degree to which Fe(2+) oxidation is rusticyanin dependent and whether mutants lacking rusticyanin can be obtained. The following points were demonstrated: Addition of rusticyanin in catalytic quantities to membranes depleted of the protein increased the rate of iron oxidation by up to 10-fold. Mutants of T. ferrooxidans were isolated that exhibited wild-type sulfide oxidase activity correlated with the absence of rusticyanin. When grown at pH2 on FeSO(4), T. ferrooxidans was highly resistant to common antibiotics, yet it displayed greater sensitivity when grown at pH5 on sulfur. Thus, the basis for a genetic improvement system for T. ferrooxidans has been demonstrated.