Bacterial oxidation technology is a competitive alternative for treating refractory gold. The utilization of bacterial oxidation in the mining industry is relatively recent and the introduction of microbiology and biochemistry to this area is not widely understood by mining companies. Many misconceptions and misunderstandings have resulted from insufficient information. This paper describes the practical aspects of bio-oxidation technology related to the biology and physiology of bacteria in associate with the role and behavior of bacteria in bacterial oxidation.