It has become clear that less than 1% of microorganisms
in the natural environment can be cultivated using conventional
culture techniques (1): culture media, culture conditions
and detection of microbial colonies with the naked
eye. Thus, from the viewpoint of applied microbiology, it is
necessary to develop new methodologies that allow us to
cultivate and isolate unculturable microorganisms, leading
to the exploitation of their new functions.
In the field of investigational search for new biologically
active substances, where more than 10,000 secondary metabolites
of microbial origin have been discovered, the possibility
of finding a new compound with practical significance
using conventional methodologies of microbial isolation
and assay is remote. A new collection of novel microorganisms
is needed. Particularly, actinomycetes are important
microorganisms since more than 90% of practical antibiotics
originate from them, and two thirds of 10,000 biologically
active substances of microbial origin are produced
by them.
Thus, we have studied the cultivation and isolation of microorganisms
that nature can cultivate but researchers cannot
(2).
This paper deals with the discovery of several bacterial
and actinomycete strains that grow on soil-extract agar medium
but not on conventional media.