ANALYSIS OF A COMMERCIALLY IMPROVED PENICILLIUM-CHRYSOGENUM STRAIN SERIES - INVOLVEMENT OF RECOMBINOGENIC REGIONS IN AMPLIFICATION AND DELETION OF THE PENICILLIN BIOSYNTHESIS GENE-CLUSTER

Several commercially improved strains of Penicillium chrysogenum have been shown to carry amplifications of the entire penicillin biosynthes is gene cluster, Analysis previously carried out using the strain BW 1 890 has here been extended to the characterisation of other members of the SmithKline Beecham strain improvement series, We have determined the length of the amplicon to be 57.4 kb and shown a general increase in copy number and penicillin titre through the series, Sequence analy ses of the promoter regions of the acvA, ipnA and aat genes in the hig h titre strain BW 1901, and comparisons with wild-type sequences have not identified any potentially titre-enhancing mutations, In addition, cDNA screening has failed to identify any further transcribed element s within the co-amplified region, The homogeneity of hybridisation pat terns and the identification and analysis of a single copy revertant h as shown that the amplification is of a direct tandem nature and we pr opose a model of chromatid misalignment and recombination as its mode of generation, Hybridisation analysis of penicillin non-producing muta nts has indicated the loss, in all those investigated, of the entire p enicillin biosynthesis gene cluster, similarities between the deletion junctions in these strains and comparison with previously published d ata indicating the presence of recombinogenic regions flanking the pen icillin biosynthesis gene cluster.