Evaluation of Leptospirillum ferrooxidans for Leaching

Abstract

The importance of LeptospiriUlum ferrooxidans for leach processes has been evaluated by studying the lithotrophic flora of three mine biotopes and a heap leaching operation, by percolation experiments with inoculated, sterilized ore, and by morphological, physiological, and genetic investigations of pure and mixed cultures of L. ferrooxidans, Thiobacillus ferrooxidans, and Thiobacillus thiooxidans. In biotopes of 20°C or above, Leptospirillum-like bacteria are as abundant as T. ferrooxidans. Leptospirilli represent at least one-half of the ferrous-iron-oxidizing population. Percolation experiments confirmed this result. Leptospirilli were as numerous as T. ferrooxidans. At reduced temperatures, the generation times of leptospirilli increase more so than those of T. ferrooxidans. At 14°C, Leptospirillum grows slowly and T. ferrooxidans dominates the population. Physiological investigations indicate that L. ferrooxidans is a strict chemolithoautotroph, metabolizing only ferrous iron and pyrite. Even an addition of 0.05% (wt/vol) yeast extract inhibited its growth. The maximum ferrous-iron-oxidizing activity of L. ferrooxidans amounts to about 40% of the activity of T. ferrooxidans. After growth on sulfidic ore, both species exhibit reduced iron-oxidizing activities, L. ferrooxidans exhibiting one-third and T. ferrooxidans exhibiting one-seventh of their maximum activities. Surprisingly, the absolute values are similar. For indirect leaching, L. ferrooxidans is as important as T. ferrooxidans. This was confirmed by the results of percolation experiments. L. ferrooxidans together with T. thiooxidans mobilized metals at least as well as T. ferrooxidans did. The best results were obtained with a mixed culture of all three species.

Interfacial activity and leaching patterns of Leptospirillum ferrooxidans on pyrite

“…The ability of L. ferrooxidans to change its physical form (pleomorphism), previously described by Sand et al [13], was also evident in this study. Fig.…”

“…As previously described [13], cells grown in soluble ferrous iron mostly present a curved rod shape (curved = helical but not long enough to encompass one full helical turn) ( Fig. 1A) and less frequently the S shape ( Fig.…”

Isolation and phylogenetic characterization of acidophilic microorganisms indigenous to acidic drainage waters at an abandoned Norwegian copper mine

“…However, other workers have recorded either similar numbers of autotrophs and heterotrophs (e.g. in a uranium waste heap in Germany, Sand et al, 1992; and AMD from an abandoned copper mine, Walton and Johnson, 1992) or else greater numbers of heterotrophic acidophiles (e.g. in sulphidic regoliths subjected to accelerated weathering in humidity cell chambers; Johnson and Roberto, 1997).…”

Characteristics of attachment and growth of Thiobacillus caldus on sulphide minerals: a chemotactic response to sulphur minerals?

“…Sulphur-oxidizing acidophiles have been recognized as playing an important role in the bioleaching of sulphide minerals (Wakao et al, 1982;Sand et al, 1992;Curutchet et al, 1996). While they alone do not accelerate the kinetics of oxidative dissolution (Lizama and Suzuki, 1988;Garcia et al, 1995), mixed cultures of iron-and sulphur-oxidizing microorganisms are found to leach sulphides at higher rates than iron-oxidizing microorganisms do in isolation (e.g.…”