Life on the Wind


09 September 2011

Collaborative study by Dr Dave Wilkinson reveals how microbes travel the earth

LJMU’s Dr Dave Wilkinson and Symeon Koumoutsaris from the International Space Science Institute in Bern have led a team of scientists from the UK and Switzerland to investigate the remarkable distance that microorganisms may be able to blow between continents, raising questions about their potential to colonise new lands and also potentially to spread diseases.

The researchers working with LJMU were the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and the Ecole Polytechnique Fédérale de Lausanne (EPFL) the University of Neuchâtel published their results in the Journal of Biogeography last month. They used large computer models of the Earth's atmosphere to study how widely microbes could be dispersed.

The team modified computer models which were designed for studying the dispersal of dust particles. They looked at what would happen if they released virtual microbes from both the southern tip of South America and also from Mexico. Once airborne, microbes of 0.02mm in diameter and below can easily travel thousands of kilometres

Dr Wilkinson, Reader in Environmental Science at the School of Natural Science and Psychology, explained:

"Microbes less than 0.009 mm across went as far as Australia! These sizes would include microbes such as bacteria and many amoebae and also some fungal spores.  We found that for smaller microbes, once airborne, dispersal is remarkably successful over a 1-year period. The most striking results are the extensive within-hemisphere distribution of small virtual microbes and the lack of dispersal between the Northern and Southern Hemispheres during the year-long time-scale of our simulations.

"What our models show is that only the smallest microbes travel easily between continents. The larger ones (i.e. Larger than 20µm but still much smaller – 500 times smaller !- that the 1mm threshold previously believed to separate the "cosmopolitan organisms" from those with potential biogeographies) cannot easily travel between continents on the time span of a single year.. This is an important result as it very significantly increases the potential for microbial diversity."

The global dispersal of soil living microbes is a long standing research interest of Wilkinson and of Prof Edward Mitchell (now at the University of Neuchatel) - one of the papers co-authors.

Most microbes carried by wind are likely to be harmless, but outbreaks of certain disease such as meningitis in the Sahel region of Africa and foot and mouth disease have been linked to airborne microbes in the past.

Dr Wilkinson continued:  "We stress that our model looks at only one aspect of microbial dispersal – namely airborne transport to a new site. Once a microbe arrives, it clearly needs to reproduce, including potentially competing with microbes already at that location. Given the ease with which the smaller microbes disperse in our model it is possible that this (rather than dispersal itself) may be the rate-limiting step in many cases of microbial range expansion and this topic should form the topic for future research in this area."

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This study is published in Journal of Biogeography. To request a media copy of the paper contact Lifesciencenews@wiley.com or +44 (0) 1243 770 375

Full Citation:  Wilkinson, D.M., Koumoutsaris, S., Mitchell, E.A.D. & Bey, I. (2011) Modelling the effect of size on the aerial dispersal of microorganisms. Journal of Biogeography.

URL to paper: http://doi.wiley.com/10.1111/j.1365-2699.2011.02569.x

The story was featured extensively in online press including Science Daily http://www.sciencedaily.com/releases/2011/08/110817075426.htm and in the print edition of the METRO with additional mentions in a variety of international publications in Spain and Greece.



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