By contrast, secondary
metabolites not coupled directly to growth are some of themost complex and important metabolites of industrial interest
(Figure 15.1b). Secondary metabolites typically share a number of
characteristics. First, they are nonessential for growth and reproduction
and their formation is highly dependent on growth conditions.
Second, they are often produced as a group of closely related
compounds and are often overproduced, sometimes in huge
amounts. And finally, many secondary metabolites are the products
of spore-forming microorganisms and production is linked to
the sporulation process itself. Virtually all antibiotics, for example,
are produced by either fungi or spore-forming prokaryotes.