AHL communication is a widespread phenomenon in biomining bacteria and seems to be involved in mineral-adhesion efficiency

Abstract

Biofilm development plays a pivotal role in the bioleaching process. Quorum sensing (QS) is recognized as one of the main regulatory ways of extracellular polymeric substances (EPS) production and biofilm formation in bacteria. Previous works revealed that Acidithiobacillus ferrooxidans ATCC 23270 strain possesses a functional QS type AI-1 system. However, there is neither available data concerning the presence of a QS system in other A. ferrooxidans strains nor any other biomining bacterial species. Thus, in this work, different strains of A. ferrooxidans (ATCC 19859, ATCC 1927, ATCC 33020, DSMZ 583, DSMZ 9464), Acidithiobacillus thiooxidans (DSMZ 504, DSMZ 9463, DSMZ 11478) and Leptospirillum ferrooxidans (DSMZ 2391, DSMZ 2705) were screened for their ability to produce QS-signaling molecules [acyl-homoserine lactone (AHLs)]. Thin-layer chromatography (TLC) analysis revealed that all the A. ferrooxidans and A. thiooxidans strains produced AHL-signaling molecules while both tested L. ferrooxidans strains did not. Nevertheless, by using bioinformatic tools to screen the genome sequence of a Leptospirillum sp. type III belonging to an AMD biofilm, a QS type AI-1 locus in which the structural organization is different from that of A. ferrooxidans has been identified. The effect of synthetic AHLs and AHL-analogues on attachment of A. ferrooxidans ATCC 23270 to pyrite was analyzed. Interestingly, preliminary results suggested that some of these molecules change the rate and extent of bacterial attachment to pyrite. The production of AHLs by A. ferrooxidans and A. thiooxidans strains, the identification of a QS type AI-1 locus in Leptospirillum sp. type III and the impact of AHLs and AHLanalogues on the pyrite adhesion of A. ferrooxidans cells open new perspectives for the (bio)mining industry to eventually improve bioleaching process and control the acid mine drainage (AMD) contamination.