The incredible distances that microorganisms may be able to blow between continents has been investigated by researchers from the UK and Switzerland, raising questions about their potential to colonize new land and the possibility of spreading disease.
The results were published this month in the Journal of Biogeography by 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. They used large computer models of the Earth's atmosphere to research how widely microbes could be dispersed.
From the International Space Science Institute in Bern, LJMU's Dr Dave Wilkinson led the team together with Symeon Koumoutsaris. They modified computer models specifically designed for researching the dispersal of dust particles. They looked for what would happen should they release virtual microbes from both the southern tip of South America and also from Mexico. Once the microbes of 0.02mm in diameter and below were airborne, they can easily travel thousands of kilometers.
Dr Dave Wilkinson, 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."
Although most microbes carried by the wind are likely to be harmless, outbreaks of some diseases, including meningitis in the Sahel region of Africa and foot and mouth disease have previously been associated with airborne microbes.
Dr Wilkinson concluded:
"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."
Written by Grace Rattue