Public yeast culture repositories such as the USDA-NRRL collection, ATCC and CBS commonly receive type strains and other industrially and academically important strains from hundreds of depositors.  Hence there is a great deal of overlap in holdings among these collections.  However, the Phaff collection stands apart from these important global repositories.  Since it is the research collection of one of the most important yeast microbiologists of the 20th century, roughly 80% of the strains in the Phaff collection are not available from any other source. Strains isolated by University of California researchers are considered the property of the University, which simplifies licensing issues. The unique contents of the collection are truly remarkable.  For example:

• In 2016 we published discovery of secretion of a unique class of glycolipids by several Rhodotorula species.
• Heirloom wine yeast strains were isolated by Bioletti and Cruess from wineries in California  and Europe before the 1940s, before commercial inocula were routinely used.  The oldest strain, a California wine yeast, has been maintained since 1893.
• The collection contains a number of pigmented yeast species, including Phaffia rhodozyma, isolated by Miller and named for Phaff, which produces astaxanthin, a natural color also found in certain algae.  While the industrially important type strain is available from other public collections, a number of additional strains are maintained only in the Phaff collection.
• Strains were isolated from habitats that have since been destroyed by human development or other factors, such as cacti in the Caribbean.
• For many species, dozens, even hundreds, of independently isolated strains besides the type strain are maintained in the collection. These have value for studies such as biogeography, phylogenomics, diversity, and ecology.
• Ribosomal sequence analysis has revealed upwards of 100 unpublished species, available from no other source.
• In 2016-2019, the yeast collections of emeritus professors W. T. Starmer and P. Ganter were acquired by the Phaff collection, adding to the already extensive geographic and species diversity. Most of these strains were not previously publicly available.