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Abstract

Dryland xeric conditions exert a deterministic effect on microbial communities, forcing
life into refuge niches. Deposited rocks can form a lithic niche for microorganisms in desert regions.
Mineral weathering is a key process in soil formation and the importance of microbial-driven
mineral weathering for nutrient extraction is increasingly accepted. Advances in geobiology provide
insight into the interactions between microorganisms and minerals that play an important role
in weathering processes. In this study, we present the examination of the microbial diversity in
dryland rocks from the Tsauchab River banks in Namibia. We paired culture-independent 16S rRNA
gene amplicon sequencing with culture-dependent (isolation of bacteria) techniques to assess the
community structure and diversity patterns. Bacteria isolated from dryland rocks are typical of xeric
environments and are described as being involved in rock weathering processes. For the first time,
we extracted extra- and intracellular DNA from rocks to enhance our understanding of potentially
rock-weathering microorganisms. We compared the microbial community structure in different rock
types (limestone, quartz-rich sandstone and quartz-rich shale) with adjacent soils below the rocks.
Our results indicate differences in the living lithic and sublithic microbial communities.