Small molecules: the lexicon of biodiversity.

The extent of microbial diversity in the Biosphere is not known (and probably never will be!). One aspect of this diversity is the production of biologically active small molecules; within the Streptomycetes alone this may be millions of compounds with an extraordinary diversity and complexity of structure. First recognised as pigments and later, in the 1950s, as antibiotics, it is now clear that the small molecules produced by microbes have many different functions in nature. This huge collection of biologically active compounds with various properties has been used as pharmaceuticals and agriculturals. They also interact with proteins and RNA with high specificity and have been shown to be regulators and effectors of diverse biochemical reactions. The use of small molecules (other than as pharmaceuticals) deserves to be explored in order to exploit microbial biotechnology to the full.