Extremophiles in Mineral Sulphide Heaps: Some Bacterial Responses to Variable Temperature, Acidity and Solution...

Area of Science:

• * Geomicrobiology
• * Biogeochemistry
• * Extremozymology

Background:

• * Heap bioleaching utilizes acidophilic extremophiles for enhanced metal extraction from mineral sulfides.
• * Microbial functions include oxidation of Fe(II) and reduced inorganic sulfur compounds (RISC), and degradation of organic compounds.
• * Environmental factors like acidity, solution composition, and temperature impact these microbial functions.

Purpose of the Study:

• * To examine the effects of variable solution acidity, composition, and temperature on key microbiological functions in heap bioleaching.
• * To assess the adaptability of bacterial species to high metal concentrations and varying pH conditions.
• * To identify critical environmental factors affecting bacterial colonization and activity in mineral sulfide heaps.

Main Methods:

• * Laboratory experiments investigating the impact of varying solution acidity, composition, and temperature.
• * Culturing and analysis of up to four bacterial species commonly found in mineral sulfide heaps.
• * Monitoring of microbial functions including Fe(II) and RISC oxidation and organic compound degradation.

Main Results:

• * Bacteria demonstrate adaptation to high concentrations of metals (Cu, Ni, Co, Zn, As), enabling function within mineral sulfide heaps.
• * Alternative metabolic pathways allow bacteria to sustain growth over an extended solution pH range.
• * Fluctuating temperatures during heap startup pose the most significant threat to efficient bacterial colonization and activity.
• * Mesophilic and moderately thermophilic bacteria populations and activity are markedly reduced during initial high-temperature phases.

Conclusions:

• * Bacterial adaptation allows for metal extraction in challenging heap bioleaching environments.
• * Temperature fluctuations, particularly during initial heap startup, critically impede microbial performance.
• * Optimizing temperature control during the early stages of heap bioleaching is crucial for successful microbial colonization and efficient metal recovery.