Metals tolerance in moderately thermophilic isolates from a spent copper sulfide heap, closely related to Acidithiobacillus caldus, Acidimicrobium ferrooxidans and Sulfobacillus thermosulfidooxidans

Abstract

Selective enrichments enabled the recovery of moderately thermophilic isolates with copper bioleaching ability from a spent copper sulfide heap. Phylogenetic and physiological characterization revealed that the isolates were closely related to Sulfobacillus thermosulfidooxidans, Acidithiobacillus caldus and Acidimicrobium ferrooxidans. While isolates exhibited similar physiological characteristics to their corresponding type strains, in general they displayed similar or greater tolerance of high copper, zinc, nickel and cobalt concentrations. Considerable variation was found between species and between several strains related to S. thermosulfidooxidans. It is concluded that adaptation to metals present in the bioleaching heap from which they were isolated contributed to but did not entirely explain high metals tolerances. Higher metals tolerance did not confer stronger bioleaching performance, suggesting that a physical, mineralogical or chemical process is rate limiting for a specific ore or concentrate.

Effects of ferrous sulfate, inoculum history, and anionic form on lead, zinc, and copper toxicity to Acidithiobacillus caldus strain BC13

“…Previous work with A. caldus strain KU reported MIC values of 65 g/L (993.9 mM) for Zn and only 1.5 g/L (23.6 mM) for Cu [26], suggesting a Zn tolerance significantly higher than that observed here, and a Cu tolerance significantly lower. This previous work did not report methods for quantifying growth, or describe the growth medium used [26], making a direct comparison difficult.…”

“…This previous work did not report methods for quantifying growth, or describe the growth medium used [26], making a direct comparison difficult. These differences may be attributable to strainto-strain variance in metal tolerance, medium composition, or possibly inoculum history.…”

Microbial behaviour under conditions relevant to heap leaching: Studies using the sulfur-oxidising, moderate thermophile Acidithiobacillus caldus

“…The concentration tolerated by At. caldus 8485 T was much lower, 1.5 g Cu L −1 (Watkin et al, 2009) but in the same study it was shown that an At caldus strain, isolated from a copper sulfide bioleached heap could tolerate >50 g Cu L −1 . That comparison shows the importance of microbial adaptation to metal-rich environments in respect of the exploitation of acidophiles in mineral sulfide processing systems.…”

Correlating Microbial Diversity Patterns with Geochemistry in an Extreme and Heterogeneous Environment of Mine Tailings

“…While low concentrations of copper ion are required for cell metabolism, high copper concentrations above specific thresholds are toxic to microbial cells because of its ability to interact with radicals (59,60). In the meantime, microorganisms with high resistance and tolerance to copper have been widely reported (61)(62)(63). It is possible that such microorganisms may become dominant in tailings with high levels of Cu 2ϩ that inhibit "normal" microbial life.…”