Global patterns in soil bacterial community composition across a continental scale

Although patterns of variation regarding macroorganisms have been studied extensively, the links between microbial biogeography and the environmental factors that shape microbial communities are largely unexplored. Here we tested the Baas Becking hypothesis for microbial community distribution by analysing the soil bacterial community from the Brazilian Pampa and King George Island, Antarctica. The genetic community structure was assessed by automated ribosomal intergenic spacer analysis (ARISA fingerprint). Bacterial patterns were quantified by using hierarchical clustering and by the detection of the shared taxonomic unities between the environments. Geographical patterns in bacterial community structure were detected by broad-spectrum (between samples from different geographic locations) and specific-spectrum (within samples from different geographic locations), suggesting that microbial communities exhibit biogeographic patterns at different scales and that, at least, some taxonomic unities have a wide distribution. These preliminary results support the idea that “everything is everywhere, but, the environment selects”.