Analysis of metatranscriptomes from an acidophilic electricity generating community treating acidic mining wastewaters

Sammanfattning: Human ́s constant need for metals requires unsustainable mining and refining of metalore. As a result, highly contaminated wastewaters are discharged in the environmentcompromising the nearby habitat together with all its life forms. Microbial fuel cells arebioelectrochemical systems (BES’s) that use microorganisms to convert organic andinorganic matter, producing electricity as the final product. This technology has shownto have great potential for application for bioremediation of wastewaters. This thesisdescribes the gene expression and the taxonomical abundance of an acidophilic,electricity generating community that was used to treat mining wastewaters in amicrobial fuel cell. A complete metatranscriptomics analysis has been performed onduplicate MFC anode acidophilic microbial community generating electricity frominorganic sulfur compounds (ISC) oxidation at extremely low pH. The analysis showsthat the most expressed genus is Ferroplasma-like, the genus Acidithiobacillus-like isfollowing along with Sulfobacillus-like and Thermoplasma-like. Some of the generaexpressed show behaviours never described before suggesting that potentially, newspecies have been selected. The reactions of the sulfur pathway are regulated mostly bytwo genera: Acidithiobacillus-like during the disproportionation of tetrathionate, andFerroplasma-like by expressing the hdr gene that catalyses the reaction from elementalsulfur to sulfite, the sulfite is then converted to sulfate. The hdr gene has not previouslybeen found in F. acidarmanus-like suggesting that the specie might have been selectedfor this trait. Acidithiobacillus-like genus has a bigger role for the energy conservationand the electron transport in the sample, however the data are not sufficient to point outwhich gene has the major role in the process. The CO2 fixation in the chamber wasconsiderably low as a result from a significant carboxysomes production, bacterialcompartiments involved in the carbon dioxide fixation. The transcripts abundanceregarding the metal resistance genes have shown low expression suggesting that thecells were not under stress. This result is indicated by the synthesis of a transcriptionalrepressor protein that had prevented a significant production of metal resistanceenzymes. Likewise, the pH homeostasis plot does not show vast transcripts abundances,indicating that the cells were thriving under conditions not far from the optimum.