For most of his career he has worked on plant metabolism, at the John Innes Centre and the Institute of Food Research, Norwich, UK and at INRA, Versailles, France, but more recently he has become interested in bacterial polyamine metabolism since his move to UT Southwestern. His current research focuses on identification of novel biosynthetic pathways for polyamines and polyamine-containing molecules, and the role of these compounds in bacterial growth and biofilm formation. He is particularly interested in how biosynthetic pathways and their associated enzymes evolve. He is also an editor of the Journal of Biological Chemistry and on the advisory board of the Biochemical Journal.