(1) Experimental isolates developed or utilized in a research program which no longer are going to be maintained by the principal researcher. These are especially valuable if other researchers want to build on the original work using the same genotypes.

(2) Experimental isolates being used by a variety of laboratories for research at the molecular level that have strong potential as model organisms.

(3) Isolates in trap cultures from novel habitats (e.g., freshwater and saltwater wetlands, soils with elevated heavy metals, etc.). These genotypes are needed to obtain better knowledge of magnitude and stability of ecotypic variation. In the collection, they are important to experimenally assess the effects of culturing on persistence or loss of valued properties.

(4) Isolates from geographic regions previously unexplored to gain new biogeographic knowledge.

(5) New or unresolved species, to continue to expand our taxonomic knowledge.