Abstract
Spatial heterogeneity in microbial communities is observed in all natural ecosystems and can stem from both adaptations to local environmental conditions as well as stochastic processes. Extremophile microbial communities inhabiting evaporitic halite nodules (salt rocks) in the Atacama Desert, Chile, are a good model ecosystem for investigating factors leading to microbiome heterogeneity, due to their diverse taxonomic composition and the spatial segregation of individual nodules. We investigated the abiotic factors governing microbiome composition across different spatial scales, allowing for insight into the factors that govern halite colonization from regional desert-wide scales to micro-scales within individual nodules. We found that water availability and community drift account for microbiome assembly differently at different distance scales, with higher rates of cell dispersion at the smaller scales resulting in a more homogenous composition. This trend likely applies to other endoliths, and to non-desert communities, where dispersion between communities is limited. At the intra-nodule scales, a light availability gradient was most important in determining the distribution of microbial taxa despite intermixing by water displacement via capillary action.
Highlights
Understanding the relationships between microbial community composition and environmental factors is key to making robust predictions of microbiome dynamics (Green et al, 2008)
Regional distance scales were investigated in February 2017 by sampling the North and the South ends of Salar Grande, a salar located in the Northern part of the Atacama Desert (Robinson et al, 2015; Figure 1)
The community composition and structure were interrogated across a total of 132 biological samples in four spatial scales ranging from major regions of the salar to micro-niches within a single halite nodule (Table 1 and Figure 1)
Summary
Understanding the relationships between microbial community composition and environmental factors is key to making robust predictions of microbiome dynamics (Green et al, 2008). Other factors such as water availability, nitrogen, temperature, pH, or salinity might be more critical (Frossard et al, 2015; Armstrong et al, 2016; Merino et al, 2019), making such systems valuable models for investigating processes influencing microbial community assembly (Schmid et al, 2020). In particular, water has been identified as the core deterministic factor for microbial community assembly (Crits-Christoph et al, 2013; Merino et al, 2019; Uritskiy et al, 2019a). Relatively few studies have investigated the relative contributions of deterministic and Desert Microbiome Spatial Diversity stochastic (i.e., non-random and random) factors to community assembly over temporal or spatial scales (Caruso et al, 2011; Feeser et al, 2018; Scola et al, 2018)
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