# QS molecules change the planktonic/mineral subpopulations distribution of moderately thermophilic leaching bacteria in pyrite and decrease leaching in chalcopyrite

## TL;DR

Quorum sensing molecules affect the distribution of bacteria in a biomining community, reducing metal leaching efficiency from sulfide minerals.

## Contribution

This study reveals how quorum sensing molecules influence microbial interactions and bioleaching performance in moderately thermophilic consortia.

## Key findings

- QS compounds reduced pyrite and chalcopyrite dissolution by inhibiting iron oxidation and mineral colonization.
- DSF compounds induced motility in Acidithiobacillus caldus and expanded Leptospirillum ferriphilum on mineral surfaces.
- High fatty acid concentrations from QS molecules triggered detoxification mechanisms in the microbial community.

## Abstract

Biomining is a sustainable alternative to conventional mineral processing that uses acidophilic microorganisms to catalyze the extraction of valuable metals from sulfide minerals. Mixed microbial consortia composed of moderate thermophiles such as Sulfobacillus and some Leptospirillum species improve metal extraction efficiency at higher temperatures compared to pure cultures of mesophiles. However, quorum sensing (QS), which regulates microbial interactions and likely influences bioleaching performance, has not been studied in these species. In this study, treatment of a moderately thermophilic biomining consortium with QS compounds, termed diffusible signal factors (DSF), reduced pyrite and chalcopyrite dissolution via an inhibitory effect on iron oxidation and mineral colonization by the mixed culture. Furthermore, QS molecules changed the distribution of planktonic/mineral subpopulations of the acidophilic species. In addition, DSF compounds induced Acidithiobacillus caldus motility and dispersion from pyrite with a concomitant expansion of Leptospirillum ferriphilum on the mineral surface while in contrast, the acyl-homoserine lactone mediated QS system repressed L. ferriphilum motility. Moreover, the addition of QS molecules induced a second response related to the detrimental effect of high concentrations of fatty acids on cells, with an activation of detoxification mechanisms. Overall, QS regulated key target microbial interactions that opens the possibility to improve chalcopyrite bioleaching in the studied consortia.