  We study how a particular spatial structure with a buffer impacts the number
of equilibria and their stability in the chemostat model. We show that the
occurrence of a buffer can allow a species to persist or on the opposite to go
extinct, depending on the characteristics of the buffer. For non-monotonic
response functions, we characterize the buffered configurations that make the
chemostat dynamics globally asymptotically stable, while this is not possible
with single, serial or parallel vessels of the same total volume and input
flow. These results are illustrated with the Haldane kinetic function.
