Assessment of long-term impact of soil contaminated with naturally occurring radionuclides on bacterial communities

The taxonomic diversity and structure of bacterial communities of soil contaminated with natural radionuclides resulting from ²²⁶Ra production activities (Komi Republic, Russia) was analyzed by sequencing a fragment of the 16S rRNA gene. The diversity indices as well as the structure and the composition of the bacterial community at high taxonomic level were corresponded to the regional profile. The Pseudomonadota and Acidobacteriota phyla are dominating while the remaining phyla account for 10% or less of the total. No seasonal differences were recorded. Despite this, the contribution of the most abundant phyla to the contaminated soil community composition varied significantly from the reference as the share of Pseudomonadota is increasing from 30.7 ± 5.4 to 37.9 ± 3.7% while Acidobacteriota on the contrary is decreasing from 21.5 ± 7.4 to 12.4 ± 3.6%. At a lower taxonomic level, such groups as Geobacter, Gaiella, Sphingomonas, Sulfuricaulis, Flavihumibacter, Rhodoplanes, and Solirubrobacter obtained competitive advantages due to their ability to thrive under oxidative stress conditions associated with high levels of radionuclides.