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Open Access Research article

Genome sequence surveys of Brachiola algerae and Edhazardia aedis reveal microsporidia with low gene densities

Bryony AP Williams1, Renny CH Lee1, James J Becnel2, Louis M Weiss3, Naomi M Fast1 and Patrick J Keeling1*

Author Affiliations

1 Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, 3529-6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada

2 Center for Medical, Agricultural and Veterinary Entomology, USDA/ARS, Gainesville, FL 32608, USA

3 Department of Pathology, Division of Tropical Medicine and Parasitology, Albert Einstein College of Medicine, Bronx, New York 10461, USA

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BMC Genomics 2008, 9:200  doi:10.1186/1471-2164-9-200

Published: 29 April 2008

Abstract

Background

Microsporidia are well known models of extreme nuclear genome reduction and compaction. The smallest microsporidian genomes have received the most attention, but genomes of different species range in size from 2.3 Mb to 19.5 Mb and the nature of the larger genomes remains unknown.

Results

Here we have undertaken genome sequence surveys of two diverse microsporidia, Brachiola algerae and Edhazardia aedis. In both species we find very large intergenic regions, many transposable elements, and a low gene-density, all in contrast to the small, model microsporidian genomes. We also find no recognizable genes that are not also found in other surveyed or sequenced microsporidian genomes.

Conclusion

Our results demonstrate that microsporidian genome architecture varies greatly between microsporidia. Much of the genome size difference could be accounted for by non-coding material, such as intergenic spaces and retrotransposons, and this suggests that the forces dictating genome size may vary across the phylum.