Towards understanding geomicrobiology of an extreme environment: characterization of a novel Acidianus species involved in iron a sulphur cycles isolated from Copahue-Caviahue acidic geothermal area

GIAVENO A.,; URBIETA M.S.; ULLOA R.; GONZALEZ TORIL E.; DONATI E.R.

COPENHAGEN

Simposio; 14th International Symposium of Microbial Ecology (ISME); 2012

Towards understanding geomicrobiology of an extreme environment: characterization of a novel Acidianus species involved in iron a sulphur cycles isolated from Copahue-Caviahue Acidic geothermal area Giaveno M. A., Urbieta M. S., Ulloa R., González Toril E., Donati E. R. Extreme environments are being studied all over the world by many different approaches, particularly the -omics techniques. However, in order to understand how microorganisms relate and impact on environment, it is useful to have them isolated and deeply characterized. Copahue-Caviahue is a geothermal region under the influence of active Copahue volcano. In this area there are many hot springs with different physicochemical conditions that also have different prokaryotic biodiversity. This natural extreme environment is an ideal place to look for new, yet undiscovered species that might help to clarify the role of microorganisms in different element natural cycles. Besides, novel species isolated from acidic high temperature environments might have many potential biotechnological uses. In this work we present a novel crenarchaea isolated from three separated acidic geothermal hot springs from Copahue-Caviahue region. ALE1 isolate is a thermoacidophilic Acidianus able to develop at a wide range of pH and temperatures, from 1.0 to 5.0 and 55° to 80° C respectively. Growth rate and culture cell density are affected by these parameters, and optimal conditions are 75°C and pH 2.5 – 3.0. One of the most surprising features of this isolate is its great ability to develop using different energy and carbon sources; it is able to grow aerobically on sulphur, tetrathionate, iron (II) and sucrose. As all members of Acidianus genus ALE1 can also develop under anaerobic conditions, but this isolate can use a wider range of substrates than the other Acidianus so far reported; it grew autotrophically using ferric iron or sulphur as electron acceptors and sulphur or hydrogen as electron donors. AFM, TEM and SEM microscopy showed ALE1 cells irregular coccus form surrounded by a regularly arrayed glycoprotein layer (S-layer). Another peculiar characteristic of this novel archaea is that it was isolated from three separated and independent hot springs (and detected by non culture methods in a fourth) but the comparison of its 16S rRNA gene sequence in NCBI data base did not show any close relatives, cultured or uncultured, found elsewhere. It appears that ALE1is an autochthonous microorganism from Copahue-Caviahue region. Its closest related species are strains of Acidianus hospitalis (91 % of sequence similarity), Acidianus infernus (90 %), Acidianus ambivalens (90 %) and Acidianus manzanensis (90 %). As regards the isolate biotechnological uses, its ability to oxidise sulphur compounds and ferrous iron at high temperature makes it potentially very useful tool for bioleaching and biooxidation, especially of refractory ores like molybdenite and chalcopyrite which are scarcely dissolved by mesophilic microorganisms. ALE1 isolate growth flexibility towards pH and temperature and its ability to use a variety of oxidation state forms of sulphur and iron, auto and heterotrophically, in aerobic and anaerobic metabolisms points to its unique role in an environment that, due to its particular physicochemical and geological conditions presents niches with all these characteristics. Even more, these different microenvironments could have been originated by metabolic activities of microorganisms like ALE1.