Biofilm formation capabilities in the bioleaching microbial consortium: A comparative genomics approach

摘要

Bioleaching of copper is driven by moderate complex groups ( consortia) of acidophilic bacteria and archaea, several of which obtain the energy needed for cell growth and metabolism from the oxidation of reduced sulfur compounds and/or iron present in sulfide minerals. Microbial adhesion to rock surfaces via biofilms has been shown to be a prerequisite for the effective mineral dissolution. However, little is known about the biofilm forming capacities of most members of these consortia and how the interactions between microorganisms may affect the formation, structure and dynamics of biofilms as bioleaching proceeds. Using comparative genomics and metabolic reconstruction strategies, we have explored the metabolic potential of 18 bioleaching bacteria to sense and move towards the mineral substrate, using chemotactic responses and to adhere to the mineral surface by expressing cellular structures involved in adhesion. Our findings indicated that all 18 bacteria could potentially participate in biofilm formation at some stage of the bioleaching process. Fourteen of these bacteria encode all structural and regulatory genes necessary for the biosynthesis and assembly of flagella and thus can potentially move towards and colonize minerals. The Gammaproteo bacteria in particular, seem to play a pivotal role during the surface adherence step, since adhesion related gene functions are more abundant in this group (61% ) than in others (22% on average). In contrast, the production of exopolysaccharides ( EPS) , required for the consolidation of the biofilm, is a more wide spread and shared trait amongst the different members of the consortia. All sequenced genomes analyzed, except for the Actinobacteria spp. and Acidithiobacillus caldus have gene clusters encoding a variety of sugar inter-conversion functions and glycosyltransferases as well as the EPS export apparatus.