|Dust storm in Timna Park is shown.|
Some of these bacteria might be pathogenic -- harmful to us or the environment -- and a few of them also carry genes for antibiotic resistance. Others may induce ecosystem functions such as nitrogen fixation. Prof. Yinon Rudich and his research group, including postdoctoral fellow Dr. Daniela Gat and former research student Yinon Mazar, in Weizmann's Earth and Planetary Sciences Department investigated the genetics of the windborne bacteria arriving along with the dust.
"In essence, we investigated the microbiome of windborne dust," says Rudich. "The microbiome of a dust storm originating in the Sahara is different from one blowing in from the Saudi or Syrian deserts, and we can see the fit between the bacterial population and the environmental conditions existing in each area."
The researchers found that during a dust storm the concentration of bacteria and the number of bacterial species present in the atmosphere rise sharply, so people walking outdoors in these storms are exposed to many more bacteria than usual.
Rudich and his team then explored the genes in these bacteria, checking for antibiotic resistance -- a trait that can arise owing to elevated use of antibiotics but also naturally, especially in soil bacteria. Antibiotic resistance has been defined by the World Health Organization as one of the primary global health challenges of the twenty-first century, and its main driver is the overuse of antibiotics. But bacteria can pass on the genes for antibiotic resistance, so any source of resistance is concerning. How many different genes for antibiotic resistance come to Israel from the various dust storms, and how prevalent are these genes?
Rudich says that the study enabled the researchers to identify a "signature" for each source of bacteria based on the prevalence of antibiotic resistant genes, which revealed whether the genes were local or imported from distant deserts. "We found that as more 'mixing' occurs between local dust and that which comes from far off, the lower the contribution of the imported antibiotic resistance genes." In other words, antibiotic resistance coming from Africa or Saudi Arabia is still a very minor threat compared to that caused and spread by human activity, especially animal husbandry. Also participating in this research were Dr. Eddie Cytryn of the Volcani Center and Prof. Yigal Erel of the Hebrew University of Jerusalem.
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