Dating the Cryptococcus gattii dispersal to the North American Pacific Northwest

Chandler C. Roe, Jolene Bowers, Hanna Oltean, Emilio DeBess, Philippe J. Dufresne, Scott McBurney, David P. Overy, Bodo Wanke, Colleen Lysen, Tom Chillerh Wieland Meyer, George Richard Thompson, Shawn R. Lockhart, Crystal M. Hepp, David M. Engelthaler

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

The emergence of Cryptococcus gattii, previously regarded as a predominantly tropical pathogen, in the temperate climate of the North American Pacific Northwest (PNW) in 1999 prompted several questions. The most prevalent among these was the timing of the introduction of this pathogen to this novel environment. Here, we infer tip-dated timing estimates for the three clonal C. gattii populations observed in the PNW, VGIIa, VGIIb, and VGIIc, based on whole-genome sequencing of 134 C. gattii isolates and using Bayesian evolutionary analysis by sampling trees (BEAST). We estimated the nucleotide substitution rate for each lineage (1.59 × 10-8, 1.59 × 10-8, and 2.70 × 10-8, respectively) to be an order of magnitude higher than common neutral fungal mutation rates (2.0 × 10-9), indicating a microevolutionary rate (e.g., successive clonal generations in a laboratory) in comparison to a species' slower, macroevolutionary rate (e.g., when using fossil records). The clonal nature of the PNW C. gattii emergence over a narrow number of years would therefore possibly explain our higher mutation rates. Our results suggest that the mean time to most recent common ancestor for all three sublineages occurred within the last 60 to 100 years. While the cause of C. gattii dispersal to the PNW is still unclear, our research estimates that the arrival is neither ancient nor very recent (i.e., < 25 years ago), making a strong case for an anthropogenic introduction.

Original languageEnglish (US)
Article numbere00499-17
JournalmSphere
Volume3
Issue number1
DOIs
StatePublished - Jan 1 2018

Keywords

  • Cryptococcus
  • Genomics
  • Molecular epidemiology
  • Mycology

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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    Roe, C. C., Bowers, J., Oltean, H., DeBess, E., Dufresne, P. J., McBurney, S., Overy, D. P., Wanke, B., Lysen, C., Meyer, T. C. W., Thompson, G. R., Lockhart, S. R., Hepp, C. M., & Engelthaler, D. M. (2018). Dating the Cryptococcus gattii dispersal to the North American Pacific Northwest. mSphere, 3(1), [e00499-17]. https://doi.org/10.1128/mSphere.00499-17