Includes abstract.Includes bibliographical references (leaves 69-75).Bioleaching has developed into a very important process for the recovery of valuable metals, particularly from low grade copper ores due to the ever increase in demand. A lag phase is present during the start-up phase of heap bioleach operations characterised by a low degree of microbial colonisation, a low ferrous iron oxidation rate and low microbial proliferation rates, ultimately resulting in a poor copper recovery rate
