A UTEX catalog number that does not contain a prefix indicates it is an axenic culture maintained on an agar slant. UTEX designates a culture as axenic based on the lack of bacterial and/or fungal contamination on test plates with final confirmation via microscopy. Since we do not perform frequent DNA analysis on our strains, the definition of axenic, as used by UTEX, is limited to what we can culture in our test media and view under the microscope.