Domestication of Local Microbial Consortia for Efficient Recovery of Gold Through Top-Down Selection in Airlift Bioreactors

Abstract

Extreme acidophiles play central roles in the geochemical cycling of diverse elements in low pH environments. This has been harnessed in biotechnologies such as biomining, where microorganisms facilitate the recovery of economically important metals such as gold. By generating both extreme acidity and a chemical oxidant (ferric iron) many species of prokaryotes that thrive in low pH environments not only catalyze mineral dissolution but also trigger both community and individual level adaptive changes. These changes vary in extent and direction depending on the ore mineralogy, water availability and local climate. The use of indigenous versus introduced microbial consortia in biomining practices is still a matter of debate. Yet, indigenous microbial consortia colonizing sulfidic ores that have been domesticated, i.e., selected for their ability to survive under specific polyextreme conditions, are claimed to outperform un-adapted foreign consortia. Despite this, little is known on the domestication of acidic microbial communities and the changes elicited in their members. In this study, high resolution targeted metagenomic techniques were used to analyze the changes occurring in the community structure of local microbial consortia acclimated to growing under extreme acidic conditions and adapted to endure the conditions imposed by the target mineral during biooxidation of a gold concentrate in an airlift reactor over a period of 2 years. The results indicated that operative conditions evolving through biooxidation of the mineral concentrate exerted strong selective pressures that, early on, purge biodiversity in favor of a few Acidithiobacillus spp. over other iron oxidizing acidophiles. Metagenomic analysis of the domesticated consortium present at the end of the adaptation experiment enabled reconstruction of the RVS1-MAG, a novel representative of Acidithiobacillus ferrooxidans from the Andacollo gold mineral district. Comparative genomic analysis performed with this genome draft revealed a net enrichment of gene functions related to heavy metal transport and stress management that are likely to play a significant role in adaptation and survival to adverse conditions experienced by these acidophiles during growth in presence of gold concentrates.

Influence of mobile genetic elements and insertion sequences in long- and short-term adaptive processes of Acidithiobacillus ferrooxidans strains

“…The strategy used aims to bypass the fragmentation of most drafts (steps 1–3), the poor annotation of MGE-related contigs (steps 4–6), and the difficulties of fully reconstructing the elements present in the dataset (step 7). For this purpose, we used information available on several integrated MGEs (iMGEs) that have been identified and described to a different extent in A. ferrooxidans 16 , 20 , 22 , 23 , 27 , 33 . Moreover, candidate MGEs derived from applying existing MGE prediction resources to two available complete A. ferrooxidans genome sequences (NC_011761, NC_011206) were used 33 , 40 .…”

Recent progress in the application of omics technologies in the study of bio-mining microorganisms from extreme environments

“…They are major participants in key metabolic pathways (carbon fixation, nitrogen metabolism, ferrous iron oxidation and sulfur metabolism). High-resolution targeted metagenomics technology has been used to analyze the changes in the community structure during adaptation to extreme acidity and high concentrations of gold concentrate pulp for a long time [48]. The genomes of the dominant strains in this community (A. ferrooxidans etc.)…”

Performance and Mechanism of Hydrothermally Synthesized MoS2 on Copper Dissolution

“…Wet treatment can reduce crushing costs and avoid secondary dust pollution, but the operation is complicated and inefficient [7,8]. The microbial treatment cycle is long and easily affected by the environment [9]. The production temperature of fire treatment is as high as 1000 • C, the production investment is significant, and the energy consumption is excessive.…”