Over the last few decades, one element common to these factions has been identified: S-ribosylhomocysteinase, more commonly referred to as LuxS. This enzyme was originally thought to be involved in cell to cell communication, known as quorum sensing. Bacteria use LuxS to produce a signal, known as an autoinducer, to talk with other cells. This would then in turn lead to a community-wide set of actions, such as increasing cell density, forming biofilms or even produce defensive chemicals to avoid an attack. But another mechanism became evident as researchers took a closer look inside the cell.