Genome reduction in Leptospira borgpetersenii reflects limited transmission potential
- Dieter M. Bulach*,†,
- Richard L. Zuerner‡,§,
- Peter Wilson¶,
- Torsten Seemann†,
- Annette McGrath¶,
- Paul A. Cullen*,†,
- John Davis¶,
- Matthew Johnson¶,
- Elizabeth Kuczek¶,
- David P. Alt‡,
- Brooke Peterson-Burch‡,
- Ross L. Coppel†,‖,
- Julian I. Rood*,†,‖,
- John K. Davies*,†,‖, and
- Ben Adler*,†,‖
- *Australian Bacterial Pathogenesis Program,
- †Victorian Bioinformatics Consortium, and
- ‖Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Department of Microbiology, Monash University, Victoria 3800, Australia;
- ‡Bacterial Diseases of Livestock Research Unit, National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, Ames, IA 50010; and
- ¶Australian Genome Research Facility, Gehrmann Laboratories, University of Queensland, St. Lucia, Queensland 4072, Australia
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Edited by Harley W. Moon, Iowa State University, Ames, IA, and approved August 4, 2006 (received for review May 16, 2006)
Abstract
Leptospirosis is one of the most common zoonotic diseases in the world, resulting in high morbidity and mortality in humans and affecting global livestock production. Most infections are caused by either Leptospira borgpetersenii or Leptospira interrogans, bacteria that vary in their distribution in nature and rely on different modes of transmission. We report the complete genomic sequences of two strains of L. borgpetersenii serovar Hardjo that have distinct phenotypes and virulence. These two strains have nearly identical genetic content, with subtle frameshift and point mutations being a common form of genetic variation. Starkly limited regions of synteny are shared between the large chromosomes of L. borgpetersenii and L. interrogans, probably the result of frequent recombination events between insertion sequences. The L. borgpetersenii genome is ≈700 kb smaller and has a lower coding density than L. interrogans, indicating it is decaying through a process of insertion sequence-mediated genome reduction. Loss of gene function is not random but is centered on impairment of environmental sensing and metabolite transport and utilization. These features distinguish L. borgpetersenii from L. interrogans, a species with minimal genetic decay and that survives extended passage in aquatic environments encountering a mammalian host. We conclude that L. borgpetersenii is evolving toward dependence on a strict host-to-host transmission cycle.
Footnotes
- §To whom correspondence should be addressed. E-mail: rzuerner{at}nadc.ars.usda.gov
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Author contributions: D.M.B. and R.L.Z. contributed equally to this work; D.M.B., R.L.Z., and B.A. designed research; D.M.B., R.L.Z., P.W., T.S., J.D., M.J., E.K., and D.P.A. performed research; T.S., A.M., B.P.-B., and R.L.C. contributed new reagents/analytic tools; E.K. coordinated the AGRF portion of the sequencing; D.M.B., R.L.Z., T.S., A.M., P.A.C., B.P.-B., R.L.C., J.I.R., J.K.D., and B.A. analyzed data; and D.M.B., R.L.Z., J.I.R., and B.A. wrote the paper.
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The authors declare no conflict of interest.
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This paper was submitted directly (Track II) to the PNAS office.
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Data deposition: The sequences reported in this paper have been deposited in the DDBJ/EMBL/GenBank database (accession nos. CP000348–CP000351).
- Abbreviations:
- CDS,
- coding sequences;
- IS,
- insertion sequences;
- SPase,
- signal peptidase.
- © 2006 by The National Academy of Sciences of the USA
