COMPARISON OF 2 METHODS FOR ROOT-NODULE BACTERIA PRESERVATION - LYOPHILIZATION AND LIQUID-NITROGEN FREEZING

Liquid nitrogen freezing and freeze-drying were compared as methods fo r long-term preservation of root nodule bacteria. The viability of cel ls and the maintenance of symbiotic properties were checked in the fol lowing strains: Rhizobium meliloti 1723; R. leguminosarum by. trifolii 1326; R. leguminosarum by. viciae 1026; R. leguminosarum by. phaseoli 2620; R, galegae 0702, 0716, 0720; Bradyrhizobium japonicum 2490 and B. sp. Lupinus 1614 which possess high and low growth rates. The level of prophage induction before and after preservation was estimated in five lysogenic strains: R. galegae 0703(07-2), 0703(1/OW); R. loti 180 1(18-5), 1801(18-6) and R. meliloti D1(H19). In contrast to freeze-dry ing the liquid nitrogen freezing, for the most part, was not accompani ed with a significant drop in the suspension titre and did not change the symbiotic properties of root nodule bacteria. The level of prophag e induction in some lysogenic strains after freezing was considerably lower than that after freeze-drying. The results obtained in this work demonstrated that liquid nitrogen freezing offers significant advanta ges over lyophilization.