Characterization of Microbes Carried in Dust

Abstract

There is still a lack of understanding of how soil microbial community distribution is controlled by wind erosion. This information is of international concern as eroded sediments can potentially carry away the active labile organic soil particulates containing key microorganisms involved in soil biogeochemical processes, which can have a negative impact on the quality and functional potential of the soil. Pyrosequencing techniques promises to expand our understanding of the vast microbial diversity with respect to soils that experience high rates of wind erosion; because it is able to sequence 10-100 times more DNA fragments than previous techniques (traditional cloning). Our study evaluated the bacterial diversity on coarse and fine dust collected from three different silty soils in Michigan by using a portable field wind tunnel instrument. Our results indicated that Acidobacter was the predominant bacteria in these soils as well as the predominant bacteria carried via wind dispersion in coarse and fine dust from these soil sources. Soil 1, which had higher P levels than the other 2 soils, pH was basically 6 and it had higher organic matter (OM) content (47.3-55%), while showing this order of bacterial predominance: Acidobacter, Streptomyces, Levilinea, Patulibacter and Gemmatimonas. Although Streptomyces was the second most abundant bacteria in soil source 1, fine dust did not carry this species, and Levilinea was the second most predominant bacteria in this dust. Soil 2, which had lower P levels than soil 1 (within a range of 122-136 mg P kg-1), pH of about 5.5, and an intermediate OM content (42.9%) also showed the species predominance of Acidobacter followed by Patulibacter, Conexibacter, Rhizobium and Levilinea. Three of the 5 predominant bacteria in the soil source were also predominant in the fine dust except for Conexibacter and Rhizobium. Soil 3 had the lowest OM content (16.3-20.8%) of the 3 soils evaluated, and it had an average pH of 5.7, and P levels within a range of 123-153 P mg kg-1. This soil also showed a predominance of Acidobacter followed by Patulibacter, Rhizobium, Gemmatimonas, and Conexibacter. In addition to Acidobacter in fine dust, Conexibacter and Patulibacter were also carried. The coarse dust samples collected from these 3 soils demonstrated some differences in bacterial distribution compared to the fine dust, which may indicate that fine dust dispersion caused by wind erosion is the major carrier of soil predominant bacteria. The highest abundance of Acidobacter is explained by the acidic pH of these soils, and thus, it appears that they play an important ecological role in these soils functioning. Our findings suggested that bacteria carried in coarse or fine dust represent fingerprints of the soil source, but certain specific group of bacteria was more abundant in fine dust than coarse dust, revealing different niches in these soils. We are in the process of identifying the ecological role of the bacterial groups carried in these dust samples as they can have important implications on the soil sustainability and functioning. This research is focused on coupling the diversity of the soil microbial communities carried by wind erosion with biogeochemical functionality using enzymatic activities involved in nutrient cycling. This will allow us to identify keystone microbial species-assemblages associated with biogeochemical processes of the soil source.