Abstract

Vertical zonation is a well known characteristic of hot spring microbial mats, in which microbial populations form mat layers that can be distinguished with the naked eye. But little is known about horizontal heterogeneity. We analyzed this microheterogeneity in a hot spring mat from northern Patagonia by collecting 40 samples in a 25 x 10 cm grid, and sequencing 16S rRNA genes with Illumina. Temperature within the grid ranged from 52.4 to 60.2 ºC, and a clear shift in primary producers could be seen, from Cyanobacteria dominating at the lower temperature, to Chloroflexi dominating at the higher temperature. This illustrates the complexity of these apparently uniform mats. Other major bacterial phyla detected were Bacteroidetes, Proteobacteria, Deinococcus- Thermus and Planctomycetes, but no clear patterns were observed along the gradient for these groups. A considerable number of retrieved sequences were not found in databases, suggesting a high degree of novel diversity in these mats