Adaptations of the Genus Bradyrhizobium to Selected Elements, Heavy Metals and Pesticides Present in the Soil Environment.

Rhizobial bacteria perform a number of extremely important functions in the soil environment. In addition to fixing molecular nitrogen and transforming it into a form available to plants, they participate in the circulation of elements and the decomposition of complex compounds present in the soil, sometimes toxic to other organisms. This review article describes the molecular mechanisms occurring in the most diverse group of rhizobia, the genus Bradyrhizobium, allowing these bacteria to adapt to selected substances found in the soil. Firstly, the adaptation of bradyrhizobia to low and high concentrations of elements such as iron, phosphorus, sulfur, calcium and manganese was shown. Secondly, the processes activated in their cells in the presence of heavy metals such as lead, mercury and arsenic, as well as radionuclides, were described. Additionally, due to the potential use of Bradyrhziobium as biofertilizers, their response to pesticides commonly used in agriculture, such as glyphosate, sulfentrazone, chlorophenoxy herbicides, flumioxazine, imidazolinone, atrazine, and insecticides and fungicides, was also discussed. The paper shows the great genetic diversity of bradyrhizobia in terms of adapting to variable environmental conditions present in the soil.