A COMPARATIVE-STUDY ON THE TRANSFORMATION OF ASPERGILLUS-NIDULANS BY MICROPROJECTILE BOMBARDMENT OF CONIDIA AND A MORE CONVENTIONAL PROCEDURE USING PROTOPLASTS TREATED WITH POLYETHYLENEGLYCOL

An Aspergillus nidulans strain, auxotrophic for pyrimidine, was transf ormed to prototrophy by means of microprojectile bombardment. The tran sformation frequency was somewhat lower than conventional polyethylene glycol-mediated transformation of protoplasts. However, the percentage of stable transformants was considerably higher with the biolistic ap proach. Typically, integrations of several copies of the plasmid intro duced into chromosomal DNA were observed. The effect of several parame ters, like the concentration of conidia, chamber pressure during bomba rdment and size of microprojectiles, on transformation frequencies wer e investigated and compared to previously published data on microproje ctile bombardment of fungal conidia. Optimum results (6 transformants/ mu g plasmid DNA) were obtained when 10(8) conidia were bombarded with a helium pressure of 5.5-8.3 MPa (800-1200 lb/in(2)). M5, M10 and M17 tungsten particles were equally efficient.