Characteristics Of Bacterial Community Structure In Atmospheric Particles And Effects Of Particulate Matter

The microbial components in atmospheric particulate matter(PM)have gradually attracted the research enthusiasm in academia.The structure,diversity,difference and pathogenicity of microbial communities are important entry points for understanding the microbial contamination of PM.This paper takes Hunan University as a sampling point to conduct a case study of bacterial communities in atmospheric particulates in Changsha City,and it has conducted the following research works:First of all,an Anderson eight-stage non-viable cascade impactor was used to collect airborne PM in Hunan University of Yuelu district dring the four seasons in2017.According to the particle size and season,the two groups were divided into two groups for bacterial community comparison.The bacterial community was detected by high-throughput sequencing of the 16S rRNA gene.High-throughput sequencing results showed that the bacteria in the particles had different community structure in different seasons.The order of OTU species number in the four seasons was:autumn(6589)>summer(6289)>winter(5384)>spring(4083);high-throughput sequencing annotation results displayed that the dominant bacteria phyla were Proteobacteria,Firmicutes,Actinobacteria,Bacteroidetes and Cyanobacteria,and their relative abundance in different seasons was between 1.7%and 60.51%.;the dominant genera of the four seasons were different,and the dominant genera of spring were completely different from the other three seasons,this result showed the composition of the bacteria has the distinct seasonality.The Simpson index of more than 0.99 in all four seasons indicated that the bacterial community uniformity was high;the Shannon index showed that the community richness was between 5.54 and6.39,which sorted by numerical order:autumn>winter>spring>summer,indicating that the season may be one of the factors affecting the diversity of bacterial community.The bacterial difference in the four seasons was different,and the number of Biomarkers was the highest in summer,indicating that there were the most bacteria with large abundance differences in the season,followed by winter,autumn and spring.Secondly,High-throughput sequencing results showed that the number of OTU species in different particle sizes was between 2430-6914,which was quite different,and the number order of OTU species in the 9 particle size segments was:PS-0>PS-1>PS-2>PS-3>PS-4>PS-6>PS-F>PS-7>PS-5;high-throughput sequencing annotation results displayed the dominant bacteria phyla were roughly the same,mainly Proteobacteria,Firmicutes,Actinobacteria,Cyanobacteria and Bacteroidetes which have relative abundance was between 0.41%and 65.99%;dominant bacteria genera in different particle sizes were more distinct,and the dominant bacteria genera difference between PS-6 and other particle sizes was the largest.The Simpson index showed that the bacterial community uniformity in different particle size particles was between 0.92 and 0.99,which was different but not obvious.The Shannon index indicated that the community richness was 4.39-9.14,which was quite different.It caould be speculated that the particle size can significantly affect the bacteria.The distribution of Biomarker in different particle sizes was:PS-0>PS-1>PS-7>PS-2>PS-6>PS-F>PS-3,but no Biomarker in PS-4 and PS-5.It showed that the bacteria distribution under different particle sizes was different,and it has the uniqueness of particle size distribution.Finally,the concentration of the size-segregated PM during the sampling range was 2.81-69.31?g/m~3,and the concentration distribution showed the characteristics of bimodal distribution,and peaks were mainly in the 0 stage(>9?m)and 5 stage(1.1-2.1?m),which indicated that PM was mainly concentrated on these two particle size segments.The richness(2.8-9.09)and uniformity(0.45-0.99)of bacterial communities in different graded particles were quite different.The richness of bacterial community had a significant positive correlation with the particle size(r=0.944,p<0.01),but the particle size didn't affect the uniformity of bacterial community;the concentration of PM also had no significant correlation with the richness and uniformity of the bacterial community.Analysis of?diversity of bacterial community by PCoA plot analysis by Bray Curtis distance showed that the difference of bacterial community between spring and other seasons was large.In the same season,the bacterial community in winter was quite different.In the same particle size,the bacterial community structure was very different.