Karyotype determination and gene mapping in two clinical isolates of Penicillium marneffei

Electrophoretic karyotypes from two clinical isolates of Penicillium marneffei were derived using contoured-clamped homogeneous electric field (CHEF) gel electrophoresis. Five chromosome-sized DNA fragments were resolved from each isolate. Chromosomal length polymorphisms were evident among the three largest molecules. Based upon these electrophoretic separation patterns, individual chromosomes were estimated to range in size from 2.0 to 6.3 Mbp with a total genome size of 20.6 to 21.6 Mbp. However, Southern blot analysis using a telomeric probe suggests that P. marneffei may possess as many as seven chromosomes, including two pairs of molecules that co-migrate under the CHEF separation conditions employed in this study. Hence, the total genome size of P. marneffei may be as large as 25.7 to 26.7 Mbp. Further hybridization analysis mapped four chitin synthase homologues to specific chromosomes as well as genes for chitinase, malate synthase, isocitrate lyase, isocitrate dehydrogenase, 5.8S rRNA, and 23S rRNA. The mapping analyses also suggested the existence of multiple chitinase gene homologues in P. marneffei. The collective results of this investigation provide additional foundations for facilitating the genetic characterization of P. marneffei and the molecular epidemiology of penicilliosis due to this fungus.