Abstract
The Atacama Desert is the most arid desert on Earth, focus of important research activities related to microbial biodiversity studies. In this context, metabolic characterization of arid soil bacteria is crucial to understand their survival strategies under extreme environmental stress. We investigated whether strain-specific features of two Microbacterium species were involved in the metabolic ability to tolerate/adapt to local variations within an extreme desert environment. Using an integrative systems biology approach we have carried out construction and comparison of genome-scale metabolic models (GEMs) of two Microbacterium sp., CGR1 and CGR2, previously isolated from physicochemically contrasting soil sites in the Atacama Desert. Despite CGR1 and CGR2 belong to different phylogenetic clades, metabolic pathways and attributes are highly conserved in both strains. However, comparison of the GEMs showed significant differences in the connectivity of specific metabolites related to pH tolerance and CO2 production. The latter is most likely required to handle acidic stress through decarboxylation reactions. We observed greater GEM connectivity within Microbacterium sp. CGR1 compared to CGR2, which is correlated with the capacity of CGR1 to tolerate a wider pH tolerance range. Both metabolic models predict the synthesis of pigment metabolites (β-carotene), observation validated by HPLC experiments. Our study provides a valuable resource to further investigate global metabolic adaptations of bacterial species to grow in soils with different abiotic factors within an extreme environment.
Highlights
The Atacama Desert is the most arid desert on Earth, focus of important research activities related to microbial biodiversity studies
Based on the particular soil scenario present in the Atacama Desert, two Gram-positive, rod-shaped and yellow-pigmented Microbacterium strains (CGR1 and CGR2) were isolated from soil samples collected from the Andes mountain range in the central region of the Atacama Desert (Fig. 1)
CGR1 was obtained from an acidic site with low salinity, close to the Lascar volcano, while CGR2 was isolated from an alkaline site with high electrical conductivity located near Lejía lake
Summary
The Atacama Desert is the most arid desert on Earth, focus of important research activities related to microbial biodiversity studies. Research to date demonstrates that Microbacterium from desert soils display interesting and specific features in terms of the configuration of their global metabolism, making it necessary to identify and characterize the complete set of chemical reactions that occur in Microbacterium species in order understand how they survive under extreme dry environments. In this context, a valuable tool for the systematic study of microbial metabolism of new species is the genome scale model (GEM)[9]. To date there are no manually curated GEMs for organisms from the genus Microbacterium and there is only one GEM of a bacteria from the Atacama Desert[17]
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