Extremophile extracts and enhancement techniques show promise for the development of a live vaccine against Flavobacterium columnare

The effects of temperature, ionic strength, and new cryopreservatives derived from polar ice bacteria were investigated to help accelerate the development of economical, live attenuated vaccines for aquaculture. Extracts of the extremophile Gelidibacter algens functioned very well as part of a lyophilization cryoprotectant formulation in a 15-week storage trial. The bacterial extract and trehalose additives resulted in significantly higher colony counts of columnaris bacteria (Flavobacterium columnare) compared to nonfat milk or physiological saline at all time points measured. The bacterial extract combined with trehalose appeared to enhance the relative efficiency of recovery and growth potential of columnaris in flask culture compared to saline, nonfat milk, or trehalose-only controls. Pre-lyophilization temperature treatments significantly affected F. columnare survival following rehydration. A 30-min exposure at 0 °C resulted in a 10-fold increase in bacterial survival following rehydration compared to mid-range temperature treatments. The brief 30 and 35 °C pre-lyophilization exposures appeared to be detrimental to the rehydration survival of the bacteria. The survival of F. columnare through the lyophilization process was also strongly affected by changes in ionic strength of the bacterial suspension. Changes in rehydration constituents were also found to be important in promoting increased survival and growth. As the sodium chloride concentration increased, the viability of rehydrated F. columnare decreased.