Abstract
Halites, which are typically found in various Atacama locations, are evaporitic rocks that are considered as micro-scaled salterns. Both structural and functional metagenomic analyses of halite nodules were performed. Structural analyses indicated that the halite microbiota is mainly composed of NaCl-adapted microorganisms. In addition, halites appear to harbor a limited diversity of fungal families together with a biodiverse collection of protozoa. Functional analysis indicated that the halite microbiome possesses the capacity to make an extensive contribution to carbon, nitrogen, and sulfur cycles, but possess a limited capacity to fix nitrogen. The halite metagenome also contains a vast repertory of carbohydrate active enzymes (CAZY) with glycosyl transferases being the most abundant class present, followed by glycosyl hydrolases (GH). Amylases were also present in high abundance, with GH also being identified. Thus, the halite microbiota is a potential useful source of novel enzymes that could have biotechnological applicability. This is the first metagenomic report of fungi and protozoa as endolithobionts of halite nodules, as well as the first attempt to describe the repertoire of CAZY in this community. In addition, we present a comprehensive functional metagenomic analysis of the metabolic capacities of the halite microbiota, providing evidence for the first time on the sulfur cycle in Atacama halites.
Highlights
The Atacama Desert, located in Northern Chile, is one of the oldest, arid, and most hostile deserts on Earth
The authors of [8] described a microbiome dominated by Archaea (~71%) followed of Bacteria (~27%) and a small abundance of Eukarya (~1%) in Atacama Desert halite nodules, while a microbiota dominated by Archaea (81%) has been reported in halite endolithic communities from this Desert [7]
This suggests that the relative composition of microbial communities that are present in desert rocks may vary and is likely to be influenced by many factors such as the sampling site, rock mineralogy, and its particular climatological conditions, amongst others
Summary
The Atacama Desert, located in Northern Chile, is one of the oldest, arid, and most hostile deserts on Earth. In the last two decades, it has been well documented that soils, sediments, and rocks from this poly-extreme environment harbor a rich microbiota including archaea, bacteria, fungi, protozoa, and algae, as well as viruses [1,4,5,6,7,8,9,10]. Rocks are probably the nearest-to-optimal habitats that exist in deserts, where they facilitate microbial life They act as a water reservoir, an exposed surface for water condensation (dew formation), and as natural thermoregulators that confer protection from severe temperature fluctuations. They serve as solar radiation shields to reduce photodamage derived from the high ultra-violet (UV) radiation index in arid zones [2,11,12,13]. Organisms living in associations within rocks are termed lithobionts, while those living inside of the rocks are classified as endolithic [14]
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