Karyotype of Penicillium nalgiovense and assignment of the penicillin biosynthetic genes to chromosome IV

The karyotype of Penicillium nalgiovense was determined by pulsed-field gel electrophoresis and compared to the karyotype of P. chrysogenum. Both species have four chromosomes, but they differ in the size of the chromosomes and in the overall size of the genome. The sizes of the P. nalgiovense chromosomes as determined by pulsed-field gel electrophoresis are: 9.1 Mb, 7.9 Mb, 5.4 Mb and 4.1 Mb which gives in summary a genome size of 26.5 Mb. This compares to 34.1 Mb for P. chrysogenum. The penicillin gene cluster was located by Southern hybridization on chromosome IV, the smallest chromosome of P. nalgiovense compared to chromosome I, the largest chromosome of P. chrysogenum.