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Journal of Bacteriology, December 1998, p. 6697-6703, Vol. 180, No. 24
Department of Biological Sciences, Center for
Molecular & Cellular Biosciences, The University of Southern
Mississippi, Hattiesburg, Mississippi 39406
Received 12 June 1998/Accepted 16 October 1998
The genome size, complexity, and ploidy of the dimorphic pathogenic
fungus Histoplasma capsulatum was determined by using DNA
renaturation kinetics, genomic reconstruction, and flow cytometry. Nuclear DNA was isolated from two strains, G186AS and Downs, and analyzed by renaturation kinetics and genomic reconstruction with three
putative single-copy genes (calmodulin,
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Genome Size, Complexity, and Ploidy of the
Pathogenic Fungus Histoplasma capsulatum
and
-tubulin, and
-tubulin). G186AS was found to have a genome of approximately 2.3 × 107 bp with less than 0.5% repetitive sequences. The Downs
strain, however, was found to have a genome approximately 40% larger
with more than 16 times more repetitive DNA. The Downs genome was
determined to be 3.2 × 107 bp with approximately 8%
repetitive DNA. To determine ploidy, the DNA mass per cell measured by
flow cytometry was compared with the 1n genome estimate to
yield a DNA index (DNA per cell/1n genome size). Strain
G186AS was found to have a DNA index of 0.96, and Downs had a DNA index
of 0.94, indicating that both strains are haploid. Genomic
reconstruction and Southern blot data obtained with
- and
-tubulin probes indicated that some genetic duplication has occurred
in the Downs strain, which may be aneuploid or partially diploid.
*
Corresponding author. Mailing address: The University
of Southern Mississippi, Department of Biological Sciences, Center for Molecular & Cellular Biosciences, Box 5018, Hattiesburg, MS 39406. Phone: (601) 266-4722. Fax: (601) 266-5797. E-mail:
glen.shearer{at}usm.edu.
Present address: William Beaumont Hospital, Dept. of Clinical
Pathology, Royal Oak, MI 48073.
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