Storage of Conidia of Penicillium chrysogenum in Liquid Nitrogen

Conidiated slope cultures of derivative of Penicillium chrysogenum Wis 54-1255 were stored at -196 or +4 C for a period of 3.5 years. After this time, the viability fell to 68% in the former case and to 4% in the latter. At the end of the experiment, 65 single conidial isolates from each series were tested for penicillin yield. Among those from conidia stored at -196 C, the spread of penicillin yields did not differ markedly from that of 65 single conidial isolates made as controls prior to storage. However, 18% of those from conidia stored at +4 C formed a subpopulation with substantially lower penicillin titers than those of control isolates. Storage at -196 C may reduce or prevent a possible source of penicillin yield decay, namely, the selection of spontaneous mutants of low titer present in small numbers in the original culture and selected, as viability decreased, by virtue of their increased longevity relative to that of the parental culture.     

Transfection of wild-type and 'Fanconi anemia-like' mouse lymphoma mutant cells by electroporation

An electroporation protocol for the successful transfection of mouse lymphoblastoid cells has been developed. Two cell lines, a normal and a mutant sensitive to DNA cross-linking agents, were used. The optimum conditions of electroporation in terms of uptake of the fluorescent dye lucifer yellow coupled with low toxicity were established. Subsequently, these conditions were used to achieve stable transfection by a plasmid expression vector. The plasmid integration patterns were determined by Southern blot analysis.