Accumulation of environmental stress responses in bacteria is known to influence genomic variation.1-3 This is of particular concern for microbial reference strains that are used for industrial process verification as well as applied research. When it comes to use of reference strains, there could be two principal avenues where bacterial stress is introduced: one originating from the culture conditions and the other from the preservation strategies used. As both processes can modulate bacterial stress responses, improper culture and preservation techniques may lead to genomic variation in bacterial reference strains.