Microbes growing on Patches of glacial sediments

We sampled discreet biological Soil Crusts (BSC) micro-colonies growing near the snout of a retreating glacier in the high Arctic and show that BSCs have higher 16S diversity than the simpler communities of bare sediments sampled next to each colony. Surprisingly, the colonies also had a higher degree of phylogenetic dispersion than the phylogenetically clustered bare sediment controls. There were only eight 16S phylotypes (ASV) that showed 100% prevalence in all 12 of the colonies. The three most abundant of these keystone ASVs were cyanobacteria, including a nitrogen fixing Nostoc. This prominence of phototrophs indicates that early-successional BSC colonies are being supported by photosynthesis rather than ancient- or aeolian-derived organic matter. Overall, our fine-scaled sampling revealed new insights into community assembly and function in actual communities of interacting microbes (as opposed to mixed communities in bulk soil samples) during the early stages of primary succession.