[Frozen and thawed bacteria as recipients of isolated phages and plasmid DNA].

Bacteria subjected to freezing and thawing are effective recipients of phage 1 phi 7 DNA, lambda DNA, and plasmid pMB9 DNA. The effectiveness of transfection and plasmid transformation of frozen and thawed bacteria is determined by the joint action of 3 factors: 1) the conditions of freezing and thawing of a recipient and DNA mixture with freezing carried out at a rate of 400 degrees C/min to--76 degrees C or--196 degrees C and with subsequent thawing at 42 degrees C; 2) a transitory character of recipient competence preservation in respect of phage and plasmid DNA; 3) the degree of recipient cryolability depending, in particular, on the genotype of the recipient. The maximum indices of transfection effectiveness and plasmid transformation have been obtained with bacterial concentration equal to 1--5 X 10(9) cells/ml, phage and plasmid DNA concentration equal to 0.05--0.5 mcg/ml in the reaction mixture containing 0.5--1% of Spofa bactopeptone, PH 7.4--7.6.