Investigation of airborne bacterial abundance and their diversities during occurring fine dust storms in Lorestan province

BACKGROUND AND OBJECTIVES Dust storms are natural phenomena occurring more in arid and semi-arid regions that have adverse effects on ecosystems and human health. Dispersion of microorganisms via dust storms to a faraway is one of the important aspects of microbial ecology and air microbiology. The aim of this study was to investigate the airborne bacteria abundance and it diversity during occurring dust storms in some cities of Lorestan province using the classical methods.MATERIALS AND METHODSIn the cross-sectional descriptive study, sampling of air dust were carried out in three cities of Lorestan province with different geographical locations. The sampling was performed according to the standards of the American Environmental Protection Agency (EPA) by passive sedimentation method on R۲A, TSA culture media. Airborne bacteria were isolated and identified using classical methods and the data analysis was performed by Chi-square test. The relationship between bacterial abundance and meteorological parameters were investigated and analyzed using Spearman`s correlation test.RESULTS AND DISCUSSIONIn this study showed that ۲۰۰ colonies grew on TSA medium. Of these colonies ۶۷.۵% were bacteria and the rest (۳۲.۵%) were yeast. The microbial frequency at Khoramabad station was the lowest at ۳% and at kohdasht station was the highest (۳۱.۵%). On R۲A culture medium, ۱۹۶ colonies grew that ۶۷.۸% of these colonies were bacteria and ۳۲.۲% were yeast. Poldakhtar station had the highest microbial frequency with ۲۶.۵% and Khorramabad station had the lowest bacterial frequency at ۹.۲%. In TSA and R۲A culture media, the highest isolates were Bacillus and the lowest one was Staphylococcus. Furthermore, the highest microbial frequency was detected in Kohdasht and Poldakhter. Based on the Spearman correlation test, a direct relationship was observed between the amount of dust and the abundance of bacteria (r = ۰.۵۸۱, pv = ۰.۰۴۵), while an inverse linear relationship was observed between the wind speed and the number of colonies (r= - ۰.۶۱۹, pv = ۰.۰۳۸). There was no significant relationship among temperature, humidity and abundance of bacteria. Moreover, identification of yeast strains were not the object of this study.CONCLUSION Bacterial abundance was higher in R۲A culture medium. Gram-positive bacteria were isolated in both TSA and R۲A media. In this study no gram-negative bacteria were isolated. Bacillus and Micrococcus were the dominant bacteria in both R۲A and TSA culture media. One of the main reasons for presence of these bacteria is formation of spore and production of pigments. Both these characteristics help these microorganisms to survive in dryness and other harsh environmental conditions. It can be concluded that the amount of fine dust and wind speed affected the abundance and diversity of airborne bacteria.

کلیدواژه ها:

Fine Dust ، Lorestan ، Meteorological Parameters ، Microbial Contamination