L- Lysine lactam is the cyclic amine formed by the dehydration of the amino acid, lysine. L- Lysine lactam is a common synthetic by-product of peptide chemistry using lysine and requires protection of the amino group to avoid cyclisation. The formation of lysine lactam as a biosynthetic component of secondary metabolites (e.g. bengamides) is well recognised but while other cyclic amino acids such as homoserine lactones were the basis of our understanding of bacterial quorum sensing, the biological role of L- Lysine lactam has been unexplored.