Microbial Characterization of Microbial Ecosystems Associated to Evaporites Domes of Gypsum in Salar de Llamara in Atacama Desert

Abstract

The Central Andes in northern Chile contains a large number of closed basins whose central depression is occupied by saline lakes and salt crusts (salars). One of these basins is Salar de Llamara (850 m a.s.l.), where large domed structures of seemingly evaporitic origin forming domes can be found. In this work, we performed a detailed microbial characterization of these domes. Mineralogical studies revealed gypsum (CaSO(4)) as a major component. Microbial communities associated to these structures were analysed by 454 16S rDNA amplicon sequencing and compared between winter and summer seasons. Bacteroidetes Proteobacteria and Planctomycetes remained as the main phylogenetic groups, an increased diversity was found in winter. Comparison of the upper air-exposed part and the lower water-submerged part of the domes in both seasons showed little variation in the upper zone, showing a predominance of Chromatiales (Gammaproteobacteria), Rhodospirillales (Alphaproteobacteria), and Sphingobacteriales (Bacteroidetes). However, the submerged part showed marked differences between seasons, being dominated by Proteobacteria (Alpha and Gamma) and Verrucomicrobia in summer, but with more diverse phyla found in winter. Even though not abundant by sequence, Cyanobacteria were visually identified by scanning electron microscopy (SEM), which also revealed the presence of diatoms. Photosynthetic pigments were detected by high-performance liquid chromatography, being more diverse on the upper photosynthetic layer. Finally, the system was compared with other endoevaporite, mats microbialite and Stromatolites microbial ecosystems, showing higher similitude with evaporitic ecosystems from Atacama and Guerrero Negro. This environment is of special interest for extremophile studies because microbial life develops associated to minerals in the driest desert all over the world. Nevertheless, it is endangered by mining activity associated to copper and lithium extraction; thus, its environmental protection preservation is strongly encouraged.

Bacterial Diversity in Microbial Mats and Sediments from the Atacama Desert

“…It is known that hypersaline environments have a low diversity, where halophilic microorganisms are able to survive to these extreme conditions because they have specific strategies to balance the osmotic pressure [32,33]. Moreover, it has been seen that these systems usually have very low organic carbon and nitrogen content [8,25,30,34]. The combination of these factors makes soils from these environments inhabitable only by a very low diversity of organisms, mostly bacteria and archaea, but also some fungi and protists [25,34,35].…”

“…The CCA triplot revealed significant correlations to the ten most abundant phyla detected in each sample studied. Besides, the analysis of three evaporite samples was included, two from Laguna LLamara [8] and one from Laguna Tebenquiche [9], in order to observe differences among areas. CCA axes 1 and 2 explain 77 % of total variance of the data.…”

“…These ecosystems are characterized by extreme physicochemical and climatological conditions like extreme aridity, strong winds, scarce but torrential rainfall, high rates of evaporation, high solar radiation, extreme daily temperature changes (e.g., −2 + 20°C), negative water balance (e.g., precipitation rates of <10-300 mm year −1 versus evaporation rates 1000-1200 mm year −1 ), combined with a wide range of salinity (from freshwater to saturated saltwater within the same basin) [1,[3][4][5]. The salt composition is typically dominated by sulfate, chloride, sodium, and divalent cations [3,[6][7][8][9]. In spite of these conditions, phototrophic and heterotrophic bacteria have been recently found inside halite and gypsum evaporites that form as bottom-growth crusts in the hyperarid core and microbial mats [9][10][11][12][13][14].…”

Extremophiles: photosynthetic systems in a high-altitude saline basin (Altiplano, Chile)

“…Oscillatoriales, Synechococcus, Cyanothece and Gloeocapsa groups and genus Gloeobacter) in the salar de Llamara, a salt flat basin (Salar de Llamara) located in the Atacama desert (Demergasso et al 2003). Additionally, photosynthetic pigments were detected being more diverse on the upper photosynthetic layer associated to evaporites domes of gypsum in the Salar de Llamara, where cyanobacteria and diatoms species were also detected (Rasuk et al 2014). However, there is little information about cyanobacterial communities under hypersaline condition (Dorador et al 2008).…”

Niche for high abundant extremophilic microbial communities in an ancient crater

“…Similarly, many studies have investigated the Atacama Desert (Desierto de Atacama) located as a plateau in South America along the Pacific coast to the west of the Andes mountains. It is the driest, non-polar and oldest desert on Earth (Farías et al 2014;Rasuk et al 2014Rasuk et al , 2016. Recent findings (Rasuk et al 2016) have indicated that a large proportion of 16S sequences could not be classified at the phylum level, which may indicate a new phylum is present in this Desert.…”