MINERAL SULFIDE OXIDATION BY ENRICHMENT CULTURES OF NOVEL THERMOACIDOPHILIC BACTERIA

Enrichment culture of hot spring water samples with pyrite as substrat e has provided acidophiles with novel growth characteristics: with the se bacteria, the range of conditions under which rapid microbial oxida tion of mineral sulphides has been demonstrated has been extended. The upper temperature limit for bacterial mineral oxidation in reactors h as been raised. The dissolution of pyrite occurred during growth of Su lfolobus-like thermophiles up to almost 90-degrees-C. The most efficie nt extraction of copper from chalcopyrite occurred at 80-85-degrees-C. With moderate thermophiles, rapid oxidation of minerals was obtained during autotrophic growth in the absence of supplemental CO2: a mixed enrichment culture was active in pyrite dissolution at 45-50-degrees-C in reactors gassed only with air which contrasted with poor growth by well-studied moderate thermophiles in the absence of enhanced CO2 con centrations.