Abstract
The Atacama Desert is the most extreme non-polar biome on Earth, the core region of which is considered to represent the dry limit for life and to be an analogue for Martian soils. This study focused on actinobacteria because they are keystone species in terrestrial ecosystems and are acknowledged as an unrivalled source of bioactive compounds. Metagenomic analyses of hyper-arid and extreme hyper-arid soils in this desert revealed a remarkable degree of actinobacterial ‘dark matter’, evidenced by a detected increase of 34% in families against those that are validly published. Rank-abundance analyses indicated that these soils were high-diversity habitats and that the great majority of designated ‘rare’ genera (up to 60% of all phylotypes) were always rare. These studies have enabled a core actinobacterial microbiome common to both habitats to be defined. The great majority of detected taxa have not been recovered by culture dependent methods, neither, with very few exceptions, has their functional ecology been explored. A microbial seed bank of this magnitude has significance not just for Atacama soil ecosystem resilience but represents an enormous untapped resource for biotechnology discovery programmes in an era where resistance to existing antibiotics is rapidly becoming a major threat to global health.
Highlights
The Atacama Desert located in northern Chile is the most ancient and continuously driest non-polar environment on Earth; apart from its aridity it is unique in its range of habitats, its geology and geochemistry, its elevation and topography, and its radiation intensities[5]
The principle objectives of this study were to determine how diverse actinobacterial communities are in the Atacama Desert and how big a resource this presents for biotechnology exploitation, and to dissect such diversity in terms of actinobacterial rare and previously undetected dark matter[21, 22]
Over 90,000 sequence reads were obtained from the 12 sites (Fig. 1) representing 67 actinobacterial families, 16% of which could not be assigned to validly published taxa and are regarded as putatively novel candidate families
Summary
The Atacama Desert located in northern Chile is the most ancient and continuously driest non-polar environment on Earth; apart from its aridity it is unique in its range of habitats, its geology and geochemistry, its elevation and topography, and its radiation intensities[5]. The principle objectives of this study were to determine how diverse actinobacterial communities are in the Atacama Desert and how big a resource this presents for biotechnology exploitation, and to dissect such diversity in terms of actinobacterial rare and previously undetected dark matter[21, 22]. To this end, we have applied R H Whittaker’s classic diversity indices[23] to actinobacterial diversity of a hyper-arid—extreme hyper-arid landscape at five distinct habitats covering an altitude range of approximately 900–2500 m absl. Metagenome sequencing has revealed a strong correlation between global geographic distance and biome type and the biosynthetic diversity residing in soils[25], a conclusion that strongly resonates with our decision to explore the unique and poorly studied microbiomes of the Atacama Desert
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