Genetic stability of strains preserved on LENTICULE discs and by freeze-drying: a comparison using fluorescent amplified fragment length polymorphism analysis

Fluorescent amplified fragment length polymorphism (FAFLP) analysis, a high-resolution genome fingerprinting method, was used to ascertain the DNA integrity of bacterial strains during preservation by lenticulation and by traditional freeze-drying into glass ampoules. This was achieved by comparing FAFLP genotypes of a range of paired bacterial isolates recovered from LENTICULE discs (preserved between 1995 and 2004) and from freeze-dried (FD) cultures in glass ampoules (preserved between 1966 and 2000). A choice of two endonuclease combinations EcoRI/MseI or HindIII/HhaI was used for FAFLP analysis of the five different bacterial genera comprising of 10 strains. Each of these 10 strains exhibited unique FAFLP profiles. However, there were no detectable differences between the FAFLP profiles for each of the individual strains, irrespective of their preservation format or their year of preservation. Thus, the FAFLP data suggests that LENTICULE production does not result in any detectable genetic changes during drying onto LENTICULE discs and storage for at least 5 years. The provision of such FD reference cultures on LENTICULE discs rather than FD glass ampoules will provide a cost-effective format that is easier to use.