Fundamental drivers for endolithic microbial community assemblies in the hyperarid Atacama Desert.

Victoria Meslier,Carmen Ascaso,M Cristina Casero,Jacek Wierzchos,Micah Dailey,Octavio Artieda,Jocelyne Diruggiero,P R Mccullough

doi:10.1111/1462-2920.14106

Abstract

In hyperarid deserts, endolithic microbial communities colonize the rocks' interior as a survival strategy. Yet, the composition of these communities and the drivers promoting their assembly are still poorly understood. We analysed the diversity and community composition of endoliths from four different lithic substrates - calcite, gypsum, ignimbrite and granite - collected in the hyperarid zone of the Atacama Desert, Chile. By combining microscopy, mineralogy, spectroscopy and high throughput sequencing, we found these communities to be highly specific to their lithic substrate, although they were all dominated by the same four main phyla, Cyanobacteria, Actinobacteria, Chloroflexi and Proteobacteria. Our finding indicates a fine scale diversification of the microbial reservoir driven by substrate properties. The data suggest that the overall rock chemistry and the light transmission properties of the substrates are not essential drivers of community structure and composition. Instead, we propose that the architecture of the rock, i.e., the space available for colonization and its physical structure, linked to water retention capabilities, is ultimately the driver of community diversity and composition at the dry limit of life.

Highlights

Desertification is increasing around the world as the result of human activity and climate change (Barnett et al, 2005)
Forty-seven samples from 4 different rock substrates were collected from two sampling sites, Valle de la Luna area (VL) and Monturaqui area (MTQ), located in the hyper-arid zone of the Atacama Desert (Figure 1 and Supplementary information S1)
We addressed the drivers promoting the assembly of endolithic microbial communities in different substrates all collected in the same hyper-arid climate regime of the Atacama Desert

Summary

INTRODUCTION

Desertification is increasing around the world as the result of human activity and climate change (Barnett et al, 2005). Often considered as the last refuge for life in extreme deserts, the endolithic habitat provides protection against harmful solar irradiance, enhances the water budget by up-taking and retaining water, buffers high thermal fluctuations, and provides physical stability to microbial communities (Friedmann 1980; Walker and Pace 2007; Wierzchos et al., 2012a). Characterization of the structure and composition of these communities has shown that endoliths all harbor phototrophic primary producers, co-occurring with a wide range of heterotrophic consumers, and seeded from a “metacommunity”, i.e. a microbial reservoir available for colonization (Walker and Pace 2007; Wierzchos et al, 2012a). Within the same climate regime, we found endolithic communities highly specific to their substrates, suggesting a fine scale diversification of the available microbial reservoir

RESULTS

DISCUSSION

EXPERIMENTAL PROCEDURES