A Novel <i>Acidianus</i> Strain Isolated from Copahue, Argentina Involved in the Sulphur Cycle of a Volcanic Environment

Abstract

The extremely thermophilic archaea have become a research hotspot in the recent years because of their extreme living conditions, physicochemical characteristics such as the oxidation of sulphur, metal sulphide ore and excellent leaching capability of metal sulphides. A novel thermoacidophilic archaea (ALE1 strain) of the genusAcidianus,CandidatusAcidianus copahuensis, was isolated from the Copahue Volcano area, in Neuquén, Argentina. This strain was able to metabolize different sulphur compounds under aerobic and anaerobic conditions. ALE1 strain was inoculated in M88, a selective medium for thermoacidophilic archaea recommended by DSMZ. Elemental sulphur (So) and potassium tetrathionate (T) were used alternatively as the energy source, while oxygen and iron (III) were the electron acceptors in the aerobic and anaerobic tests respectively. All systems were incubated at 70oC in shake flasks. The pH, Eh, [H+] and cell concentration were measured. The results from the aerobic test confirm that ALE1 strain was able to oxidize (So) and (T) decreasing the pH significantly, reaching the values 1 and 1.5, respectively. A light yellow precipitate was formed only in the inoculated systems in presence of (T). It was characterized by SEM and FTIR techniques showing that only sulphur atoms are bonded together in some way not confirmed yet. In the anaerobic tests, it was found that ALE1 was able to oxidize sulphur and tetrathionate ion transferring electrons to iron (III) acceptor. The Eh decreased in all inoculated systems from nearly 500mV to 300mV approximately. This work shows that ALE1 strain is helping to keep active the sulphur cycle in the Copahue volcanic environment; however the challenge is to elucidate the metabolism involved.