Visualization of attachment and colonization of pyrite surfaces by a novel species of Acidianus

CAMILA CASTRO, MARIO VERA, EDGARDO DONATI, WOLFGANG SAND

Simposio; 20° Simposio Internacional de Biohidrometalurgia; 2013

It is well known that attachment of leaching microorganisms to the mineral surface enhances metal sulphide (MS) dissolution, because most of the leaching reactions occur directly at the mineral surface/interface, with the extracellular polymeric substances (EPS) playing a fundamental role. Microorganisms can strongly increase EPS production in order to build biofilms. That is why the studies about attachment and EPS productions are significant to learn how to improve and enhance the leaching efficiency. In this work we have studied the attachment and colonization on pyrite surfaces by the recently isolated thermophilic archaeon Candidatus Acidianus copahuensis (from the geothermal Caviahue-Copahue system, Argentina) with cells adapted to growth with sulphur, iron (II) or pyrite. In order to characterize the EPS glycoconjugates of this Acidianus strain, some fluorescent lectins with FITC or TRITC labelling were tested and TRITC-ConA was selected as a lectin with the best signal. Attachment tests were done in Erlenmeyer flasks containing coupons or grains of pyrite. The flasks were inoculated and incubated at 65°C. Coupons and grains were taken after one, three and seven days of incubation, and attachment was observed semiquantitatively by microscopic techniques. Coupons and grains of pyrite were treated with DAPI (to stain attached cells) and TRITC-ConA (to stain polysaccharides from EPS). Pyrite surfaces were imaged by epifluorescence and confocal laser microscopy. It was observed that the cell adhesion correlated with the increased of EPS production; both processes were favoured when cells were adapted to growth with pyrite. Also the effect of phosphate in the adhesion of Acidianus was studied in similar tests using a base medium without phosphate. An increase of cell adhesion under phosphate starvation conditions was detectable.