rhizobacteria (on steriods)
An early frost ended my Limas. So I pulled the vines to make way for a cover crop of clover. To my surprise the roots were covered in what makes the legumes a legume, rhizobacteria nodules. The ability to convert nitrogen from the air into a soluble slow release fertilizer for the garden is what this bacteria does and it is stored in root nodules of all legumes and no other plant. Below is a picture of what I found as I pulled up the vines.
and a closer view