Builders, tenants, and squatters: the origins of genetic material in modern stromatolites

Abstract Micro‐organisms have long been implicated in the construction of stromatolites. Yet, establishing a microbial role modern stromatolite growth via molecular analysis is not always straightforward because DNA stromatolites can multiple origins. For example, genomic material could represent microbes responsible for (i.e., “builders”), that inhabited structure after it was built “tenants”), or microbes/organic matter were passively incorporated from water column later diagenetic fluids “squatters”). Disentangling micro‐organisms construction, already difficult systems, becomes more as organic signatures degrade, and their context obscured. To evaluate our ability to accurately decipher formation geologically recent settings, 16/18S SSU rRNA gene sequences analyzed three systems where well understood: (a) an actively growing silicic hot spring Yellowstone National Park, Wyoming, controlled by cyanobacteria; (b) mixed carbonate silica precipitate Little Hot Creek, Long Valley Caldera California has both abiogenic biogenic components accretion; (c) near‐modern lacustrine Walker Lake, Nevada likely abiogenic. In all cases, largest percentage recovered sequences, especially when focused on deeper portions structures, belonged either tenant squatter communities, actual builders. Once removed environmental context, correct interpretation biology's morphogenesis difficult. Because high‐throughput may easily lead incorrect assumptions even these caution must be exercised interpreting micro‐organismal involvement accretionary structures throughout rock record.