FREEZE-DRYING OF FLAVOBACTERIUM-COLUMNARE, FLAVOBACTERIUM-PSYCHROPHILUM AND FLEXIBACTER-MARITIMUS

Freeze-drying of bacteria requires the use of a cryoprotective agent. Skim milk, polyvinylpyrrolidone, dextran, sodium glutamate, sucrose, h orse or calf serum are all routinely used. The effects of 7 suspending media, each containing 1 of these cryoprotective additives, were stud ied on 3 strains each of 3 fish pathogenic gliding bacteria (Flavobact erium columnare, Flavobacterium psychrophilum and Flexibacter maritimu s). The viability of preserved bacteria was evaluated by colony enumer ation on Anacker and Ordal medium (Fa. columnare and Fa. psychrophilum ) and on Difco marine medium 2216E (Fx. maritimus), 48 and 72 h after inoculation. The data show the 3 bacterial species to be optimally pre served in suspending media containing Difco Bacto Brucella Broth (2/3) supplemented with either horse or foetal calf serum (1/3).