Microbes travel remarkable distances with the wind

In a study published in the Journal of Biogeography, investigators from the UK and Switzerland have researched the ability of the microorganisms to move across continents and travel unbelievable distances, raising concerns regarding their prospective capability to inhabit new areas and the probability of spreading disease.

The study involved scientists from Liverpool John Moores University (LJMU), Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and the Ecole Polytechnique Fédérale de Lausanne (EPFL) the University of Neuchâtel.
In order to establish how extensively microbes could be dispersed, the researchers used large computer models of the Earth’s atmosphere.

The team was led by Symeon Koumoutsaris along with LJMU’s Dr Dave Wilkinson from the International Space Science Institute in Bern.

Computer models exclusively designed for studying the scattering of dust particles were modified by researchers. Scientists tried to examine the outcome of releasing virtual microbes from both the southern tip of South America and from Mexico. They found that microbes of diameter 0.02 mm and below could easily travel thousands of kilometers once they were airborne.

Dr Dave Wilkinson of the LJMU School of Natural Science and Psychology said: “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 500 times smaller than 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.”

Previously, certain disease outbreaks including meningitis in the Sahel region of Africa and foot and mouth disease have been linked with airborne microbes, even though most microbes dispersed in the wind are mostly harmless.
To conclude, Dr Wilkinson said: “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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