sentences:  In 1974, he and his graduate student, Mary Green, along with Paul Heidger, a faculty collaborator, published two landmark companion papers in the journal "Infection and Immunity".The papers detail how L-form bacteria inside an experimental human embryonic kidney tissue culture system are able to persist in cells and explains how they are able to revert into the cell wall-containing parent bacterial form.They also proposed a detailed reproductive cycle for L-form bacteria, followed by electron microscopy of the microorganisms.