Rhodobacter sp. Rb3, an aerobic anoxygenic phototroph which thrives in the polyextreme ecosystem of the Salar de Huasco, in the Chilean Altiplano
The Salar de Huasco is an evaporitic basin located in the Chilean Altiplano, which presents extreme environmental conditions for life, i.e. high altitude (3800 m.a.s.l.), negative water balance, a wide salinity range, high daily temperature changes and the occurrence of the highest registered solar radiation on the planet (> 1200 W m−2). This ecosystem is considered as a natural laboratory to understand different adaptations of microorganisms to extreme conditions. Rhodobacter, an anoxygenic aerobic phototrophic bacterial genus, represents one of the most abundant groups reported based on taxonomic diversity surveys in this ecosystem. The bacterial mat isolate Rhodobacter sp. strain Rb3 was used to study adaptation mechanisms to stress-inducing factors potentially explaining its success in a polyextreme ecosystem. We found that the Rhodobacter sp. Rb3 genome was characterized by a high abundance of genes involved in stress tolerance and adaptation strategies, among which DNA repair and oxidative stress were the most conspicuous. Moreover, many other molecular mechanisms associated with oxidative stress, photooxidation and antioxidants; DNA repair and protection; motility, chemotaxis and biofilm synthesis; osmotic stress, metal, metalloid and toxic anions resistance; antimicrobial resistance and multidrug pumps; sporulation; cold shock and heat shock stress; mobile genetic elements and toxin–antitoxin system were detected and identified as potential survival mechanism features in Rhodobacter sp. Rb3. In total, these results reveal a wide set of strategies used by the isolate to adapt and thrive under environmental stress conditions as a model of polyextreme environmental resistome.
KeywordsEnvironmental resistome Alphaproteobacteria Extremotolerance Microbial mat
We thank Juan Ugalde for support in bioinformatic analysis. We thank Jaime Guerrero, Pedro Luca, Margarita Luca for assistance during field trips.
This research was supported by Grants Fondecyt No. 1140179, No. 1140356 and CeBiB FB0001. Vilma Pérez is the recipient of a Conicyt PhD scholarship.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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