Abstract

The endorheic basins found in northern Chile host several salt flats. However, the Salar de Llamara is the only active salar in the Atacama Desert sensu stricto. Until now, metagenomic analyzes carried out in the Puquios of that system only considered isolated sites and/or a single station. Periodic and multi-site metagenomic analysis of the microbial communities that inhabit the gypsum structures (domes) at the salar were performed to build a base line and allows us to reconstruct genomes and contribute knowledge about the eco-functionality of the taxa present in this type of environments. The objective of this work is to investigate the representatives of the Rhodobacteraceae family, known for the capacity for aerobic anoxygenic photosynthesis, their abundance and diversity in the salar since 2004. The DNA was extracted from gypsum structures, the metagenomes were sequenced and subsequently processed using SqueezeMeta. From this analysis, 15 metagenomes assembled genomes (MAGs) belonging to the Rhodobacteraceae family were recovered (completeness > 80% and contamination < 5%) from the different sites during 2018 and 2019 summer and winter campaigns. They were grouped into 6 clades based on their 100% average nucleotide identities. Taxonomic analysis suggested that these groups represent new species within their respective genera. All those MAGs were more abundant in the most saline Puquio (EC>150 mS/cm) and in the deeper layers (E3-E4) of the gypsum structures. Only representatives of Clade 1 were detected in the superficial layers (E1-E2). Interestingly, clades 1, 2 and 6 contain bacteriochlorophyll a synthesis genes and genes encoding the photosynthetic reaction center, while clades 3, 4 and 5 harbor genes encoding the Sox system suggesting a different energy source. Furthermore, the in situ genome replication index (iRep) ranged between 1.38 and 1.73 which is indicative of slow replication, except for clade 4 in Sumer 2019 (iRep value of 2.08), that indicate higher microbial activity at higher EC values. The occurrence of Bacteriochlorophyll a was evidenced as well only in the gypsum structures of the most saline Puquio. This study provides new knowledge associated with the diversity inside the Rhodobacteraceae family presumably related to its eco-funcionality in the Salar de Llamara.