The loss of plasmid-encoded phenotypes in Alcaligenes eutrophus, Staphylococcus aureus, and Pseudomonas putida during freeze-drying and storage

Three bacterial strains, which serve as hosts for plasmids containing phenotypes of environmental interest, were subjected to freeze-drying and storage. Plasmid-encoded phenotypes investigated included heavy metal resistance in A. eutrophus and S. aureus and catechol 2,3-oxygenase enzyme activity in A. eutrophus and P. putida. Both freeze-drying and storage treatments were found to affect strain viability and plasmid phenotype expression. In all cases studied, loss of strain viability was greater than 95.6% after freeze-drying. Strain viability losses were accompanied by phenotype losses which averaged an order of magnitude greater than viability losses. Viability and phenotype loss continued during storage and were described using first-order decay. The implications of these trends for application of specialized cultures to promote enhanced biodegradation are discussed.