Effect of Environmental Factors on Recombinant Activity of Root Nodule Bacteria

Abstract—

The legume–rhizobia symbiosis is a unique natural phenomenon, which supplies the plant with the necessary mineral nitrogen via fixation of atmospheric dinitrogen. This interaction involves two partners: the legume plant and root nodule bacteria (rhizobia). In the wild, members of the Fabaceae family enter into symbiosis with a polymorphic group of rhizobia specific to them; the mechanism and reasons for the formation of heterogeneity of rhizobia are currently the subject of active research. In the present work, a Rhizobium leguminosarum strain strictly specific to Phaseolus vulgaris L. was used to show that within 30 days upon its introduction into soil, genetic rearrangements occurred in the cells, as was revealed by changes in the pattern of its genetic profile. It was also found that recombination activity of the cells was also affected by the root exudates produced during seed germination, which may indicate involvement of the plant in the formation of polymorphism of its microsymbionts. These findings suggest interpretation of this process not as a spontaneous event, but rather as an event controlled by the plant.