This work was initiated under a contract with the United Kingdom Atomic Energy Authority to identify the role of Thiobacillus ferro oxidans in the leaching of minerals from low grade ores, A collection of cultures of T.ferro oxidans and other acidophilic thiobacilli, especially T.thio oxidans was made. Samples of soil and pyritic ore and water samples from mine drainage were collected both from this country and abroad from which bacteria were isolated, A method of purifying T.ferro oxidans by plating on a solid medium was developed and the conditions required for growth of colonies from single cells were found. The effect of oxygen on growth is described. This technique also allowed a viable count of the bacteria to be made. Growth rates of T.ferro oxidans on ferrous sulphate media were measured and the effects of aeration, temperature and pH of media on growth were studied. Evidence for strain variation was sought. The production of soluble ferric iron from pyrite and pyritic ores was used to estimate bacterial growth on these substrates. The growth of pure strains of T.ferro oxidans was found to be very uniform for pyrite but mixed thiobacilli cultures were found to solubilise ferric iron from pyrite at a faster rate. The ability of T.ferro oxidans to fix atmospheric nitrogen was discovered and confirmed. Conditions for nitrogen-fixation are described.
|Date of Award||1977|