First Prokaryotic Biodiversity Assessment Using Molecular Techniques of an Acidic River in Neuquén, Argentina

Abstract

Two acidic hot springs close to the crater of Copahue Volcano (Neuquén, Argentina) are the source of the Río Agrio. The river runs several kilometres before flowing into Caviahue Lake. Along the river, temperature, iron, other metal and proton concentrations decrease gradually with distance downstream. From the source to the lake and depending on the season, pH can rise from 1.0 (or even less) to about 4.0, while temperature values decrease from 70°C to 15°C. Water samples were taken from different stations on the river selected according to their physicochemical parameters. In order to assess prokaryotic biodiversity throughout the water column, different and complementary molecular biology techniques were used, mainly in situ hybridisation and 16S rRNA gene cloning and sequencing. All microorganisms found are typical of acidic environments. Sulphur-oxidizing bacteria like Acidithiobacillus thiooxidans and Acidithiobacillus albertensis were detected in every station. Moderately thermophile iron- and sulphur-oxidizing bacteria like members of Alicyclobacillus and Sulfobacillus genera were also ubiquitous. Strict iron-oxidizing bacteria like Leptospirillum and Ferrimicrobium were present at the source of the river, but disappeared downstream where iron concentrations were much lower. Iron-oxidizing, mesophilic Ferroplasma spp. were the main archaea found. The data presented in this work represent the first molecular assessment of this rare natural acidic environment.

A Deeper Look into the Biodiversity of the Extremely Acidic Copahue volcano-Río Agrio System in Neuquén, Argentina

“…Río Agrio originates as a natural acidic river due to the volcanic gases (H 2 SO 4 , HF, HCl) discharged by the hot springs that give it origin [30]. In this study, the pH measured at the origin (samples VA1 and VA2) was two (our group had measured pH values close to 1 in other campaigns [10]) and it remains almost constant all through the course of URA, in spite of the dilution effect produced by receiving multiple neutral tributary courses mainly of snowmelt origin. The dilution of URA after the origin is reflected in a decrease in conductivity, anions, and cations concentrations that starts in AS1 and becomes more drastic in CC.…”

“…At the beginning, we relied only on culture depending techniques which allowed the identification of several acidophilic iron and/or sulfur oxidizing species [32,33]. These results encourage us to perform more comprehensive assessments of prokaryotic biodiversity, such as cloning and sequencing of 16S rRNA genes of bacteria and archaea [10]. Despite finding a quite rich extreme biodiversity, both approaches were highly incomplete in the light of next-generation sequencing techniques.…”

Draft Genome Sequence of the Novel Thermoacidophilic Archaeon Acidianus copahuensis Strain ALE1, Isolated from the Copahue Volcanic Area in Neuquén, Argentina

“…The constant volcanic activity has determined the acidic, sulfur-rich, and high-temperature environments found in Copahue, such as Río Agrio and the geothermal springs (1, 2). Biodiversity studies done in Copahue (3, 4) revealed the presence of acidophilic bacteria and archaea, some of which are capable of growing at a high temperature and of using iron or sulfur compounds as energy sources. The detection of these extremophiles, most of which are yet uncharacterized and apparently autochthonous, makes Copahue a rich source of novel species with potential applications in biotechnological processes, mainly those related to biomining.…”

Physiologic Versatility and Growth Flexibility as the Main Characteristics of a Novel Thermoacidophilic Acidianus Strain Isolated from Copahue Geothermal Area in Argentina

“…Caviahue-Copahue system is characterised by the presence of acidic hot springs that are a potential source of extremophilic microorganisms, many of them not yet discovered. This volcanic geothermal area has been studied in its geology, geochemistry, volcanism and thermalism over the past 20 years [5,9,11,21,22,35] and more recently its prokaryotic biodiversity has been assessed [3,4,34]. However, no new indigenous extremophilic species have been reported yet from this area.…”