Microbial diversity across a natural extremely acidic environment: the Amarillo river, La Rioja, Argentina

BERNARDELLI, CECILIA; DONATI, EDGARDO; F. MASSELLO

Santiago

Simposio; 2ndo Simposio Internacional de Ecosistemas Extremos y Organismos Extremófilos; 2019

Red Latinoamericana de Extremófilos

The Amarillo River is located in the Nevados de Famatina (La Rioja, Argentina) where LaMejicana mine operated between 1890 and 1925. The river is characterized by acidic reddishyellow waters (pH~3) with high content of sulphate, metals and total dissolved solids (TDS).While the concentrations of these solutes decrease significantly downstream, pH value remainsconstant throughout the first 25 km. Therefore, the indigenous microbial community of the riverhas not only adapted to survive at extremely low pH but, also at high concentrations of metalsand substantial temperature fluctuations. In this work, we sampled three points along theAmarillo River; we extracted the genomic DNA and used high-throughput amplicon sequencingto perform culture-independent survey of the prokaryotic and eukaryotic microbial communities?structure. Besides, we made batch enrichments cultures of the samples favouring iron oxidizingacidophilic microorganisms using Mac medium (Mackintosh 1978) pH 1.8 with FeSO4.7H2O(44.7 g.L-1) with or without yeast extract (2 g.L-1) The genomic DNA of the cultures wasextracted and sequenced as well. Sequencing data was processed in R and the ampliconsequence variants (ASVs) were analyzed. The most abundant prokaryotic taxa of Amarillo Rivercommunity belonged to the phyla Actinobacteria and Proteobacteria, while the eukaryoticcommunity was dominated by Gyoerffyella spp. We did not find atrend along the river;chemolithotrophic and heterotrophic iron/sulfur oxidizing bacteria, as well as, cold tolerantfungus were identified in all three sample points. Regarding the microbial composition of thebatch cultures, the microorganisms selected were Acidithiobacillus sp., Alyciclobacillus sp.and Acidiphilum sp. Surprisingly, the first two genera were not present in abundance in thesamples. These results suggest us that classical culture-mediated techniques may selectmicroorganisms that are not representative of the sample but typical of the medium compositionand, hence, cautions should be taken when this method is used to characterize extremophilicmicrobial communities.This work was partially supported by ANPCyT, PICT-2016-2535 and PICT-2015-0463 grants.