Proteomic Characterization of Bradyrhizobium diazoefficiens bacteroids during soybean root nodules senescence

The form and physiology of Bradyrhizobium diazoefficiens after the decline of symbiotic nitrogen fixation has been characterized. Proteomic analyses showed that the post-symbiotic B. diazoefficiens undergo metabolic remodeling as well defined groups of proteins declined, increased or remained unchanged from 56 to 119 days after planting suggesting a transition to a hemibiotrophic-like lifestyle. Enzymatic analysis showed distinct patterns in both the cytoplasm and the periplasm. Similar to the bacteroid, the post-symbiotic bacteria rely on a non-citric acid cycle supply of succinate and although viable, they did not demonstrate the ability to grow within the senescent nodule.