The extremophile Acidithiobacillus ferrooxidans possesses a c-di-GMP signalling pathway that could play a significant role during bioleaching of minerals

The primary goal of this study was to characterize the existence of a functional c-di-GMP pathway in the bioleaching bacterium Acidithiobacillus ferrooxidans. A bioinformatic search revealed that the genome sequence of At. ferrooxidans ATCC 23270 codes for several proteins involved in the c-di-GMP pathway, including diguanylate cyclases (DGC), phosphodiesterases and PilZ effector proteins. Overexpression in Escherichia coli demonstrated that four At. ferrooxidans genes code for proteins containing GGDEF/EAL domains with functional DGC activity. MS/MS analysis allowed the identification of c-di-GMP in nucleotide preparations obtained from At. ferrooxidans cells. In addition, c-di-GMP levels in cells grown on the surface of solid energetic substrates such as sulfur prills or pyrite were higher than those measured in ferrous iron planktonic cells. At. ferrooxidans possesses a functional c-di-GMP pathway that could play a key role in At. ferrooxidans biofilm formation during bioleaching processes. This is the first global study about the c-di-GMP pathway in an acidophilic bacterium of great interest for the biomining industry. It opens a new way to explore the regulation of biofilm formation by biomining micro-organisms during the bioleaching process.