| Particle Size Distribution of Airborne Microorganisms and Pathogens during an Intense African Dust Event in the Eastern Mediterranean Paraskevi N. Polymenakou,1 Manolis Mandalakis,2 Euripides G. Stephanou,2 and Anastasios Tselepides1,3 1Hellenic Centre for Marine Research-Crete, Heraklion, Greece; 2Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, Heraklion, Greece; 3Department of Maritime Studies, University of Piraeus, Piraeus, Greece Abstract
Background: The distribution of microorganisms, and especially pathogens, over airborne particles of different sizes has been ignored to a large extent, but it could have significant implications regarding the dispersion of these microorganisms across the planet, thus affecting human health. Objectives: We examined the microbial quality of the aerosols over the eastern Mediterranean region during an African storm to determine the size distribution of microorganisms in the air. Methods: We used a five-stage cascade impactor for bioaerosol collection in a coastal city on the eastern Mediterranean Sea during a north African dust storm. Bacterial communities associated with aerosol particles of six different size ranges were characterized following molecular culture–independent methods, regardless of the cell culturability (analysis of 16S rRNA genes) . Results: All 16S rDNA clone libraries were diverse, including sequences commonly found in soil and marine ecosystems. Spore-forming bacteria such as Firmicutes dominated large particle sizes (> 3.3 µm) , whereas clones affiliated with Actinobacteria (found commonly in soil) and Bacteroidetes (widely distributed in the environment) gradually increased their abundance in aerosol particles of reduced size (< 3.3 µm) . A large portion of the clones detected at respiratory particle sizes (< 3.3 µm) were phylogenetic neighbors to human pathogens that have been linked to several diseases. Conclusions: The presence of aerosolized bacteria in small size particles may have significant implications to human health via intercontinental transportation of pathogens. Key words: African dust, bacterial community composition, microbial transport, particle size distribution, pathogens. Environ Health Perspect 116:292–296 (2008) . doi:10.1289/ehp.10684 available via http://dx.doi.org/ [Online 7 December 2007]
Address correspondence to P.N. Polymenakou, Hellenic Centre for Marine Research, Gournes Pediados, P.O. Box 2214, GR 71003, Greece. Telephone: 30 2810 337855. Fax: 30 2810 337822. E-mail: polymen@her.hcmr.gr Supplemental Material is available online at http://www.ehponline.org/members/2007/10684/suppl.pdf This work was supported by the European Union through the MAP program (Marine Aerosol Production ; GOCE-01832-STREP-FP6) . The authors declare they have no competing financial interests. Received 18 July 2007 ; accepted 7 December 2007.
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