Quorum sensing (QS) is the ability of microorganisms to assess local clonal density
by measuring the extracellular concentration of signal molecules that they produce
and excrete. QS is also the only known way of bacterial communication that supports
the coordination of within-clone cooperative actions requiring a certain threshold
density of cooperating cells. Cooperation aided by QS communication is sensitive to
cheating in two different ways: laggards may benefit from
not investing in cooperation but enjoying the benefit provided by their cooperating
neighbors, whereas Liars explicitly promise cooperation
but fail to do so, thereby convincing potential cooperating neighbors to help them,
for almost free. Given this double vulnerability to cheats, it is not trivial why
QS-supported cooperation is so widespread among prokaryotes.
