Characteristics Of Airborne Bacterial Community Composition In Typical Tourist City In Southern China Based On High-throughput Sequencing

Air quality is closely related to human health,and microorganisms in air,especially the pathogenic bacteria,can cause people’s allergy,asthma and respiratory infectious disease.In recent years,the frequency of haze in a wide range of our country is increasing,and wide and high attention is paid to the study on biological pollution of air;fully mastering the characteristics of microbial communities in air and the spatial-temporal variation rules is closely related to maintaining urban system and human health,and the change characteristics of air microorganisms are closely linked with urban air pollution and environmental improvement.In this research,Hangzhou,a typical southern tourist city,is taken as an example:(1)to study the concentrations and size distribution characteristics of air-borne bacteria and fungithrough air microorganism sampling with the FA-I bio-particle sampler in 4 different functional zones in Hangzhou City:traffic artery(TJCR),business street(YRBS),higher education zone(ZJGSUJC)and public park(BLQG);the concentrations and size distribution characteristics of air-borne bacteria and fungi at 4 different scenic spots in West Lake Scenic Area:Orioles Singing in the Willows(OSW),Melting Snow at Broken Bridge(MSBB),Three Pools Mirroring the Moon(TPMM)and Precious Stone Hill Floating in Rosy Clouds(PSHFRC);the concentrations and size distribution characteristics of air-borne bacteria and fungi at different heights;the relation between the concentrations of air-borne bacteria and fungiwith the pollution factors;(2)to study,through air microorganism sampling with the Coriolius μ.liquid sampler,the spatial-temporal variation characteristics of air bacterial communities in different functional zones and at different scenic spots in West Lake Scenic Area in Hangzhou City;the influence of weather characteristics on structures of air bacterial communities;the influence of different heights on characteristics of air bacterial communities;the change characteristics of structures of air bacterial communities before and after the extreme high temperature in Hangzhou City.Main research results include:(1)The spatial-temporal variations of concentrations of air-borne bacteria and fungi in Hangzhou City are significantly different,and the average concentrations of air-borne bacteria and fungi are 313CFU/m~3 and 848 CFU/m~3,accounting for 27.8%and 72.2%respectively.The maximum concentration of air-borne bacteria at YRBS is 507 CFU/m~3,and the minimum concentration at BLQG is 197 CFU/m~3.The maximum concentration of airborne fungi at ZJGSUJC is 1176 CFU/m~3,and the minimum concentration at TJCR is 557 CFU/m~3.The particle size of air-borne bacteria in Hangzhou City is of skewed distribution,and the percentages of bacterial colonies from class I to class VI decline gradually;the particle size of air-borne fungi is of lognormal distribution and is mainly distributed in classes Ⅲ,Ⅳ and Ⅴ.The characteristics of air-borne bacterial communities in Hangzhou City change significantly with the temporal-spatial variation,and the phylum-level dominant bacterial communitiesof air-borne bacteria in different seasons at 4 sampling points are Proteobacteria,Firmicutes,Bacteroidetes,Cyanobacteria and Actinobacteria,but the relative percentage contents of bacterial communities vary greatly.The characteristics of air-borne bacterial communities at different sampling points are greatly different in terms of genus level;in autumn,dominant bacterial communities at BLOG,TJCR,YRBS and ZJGSUJC are Cystobacter(9.64%),Gpl(7.32%),Deinococcus(7.41%)and Gpl(10.67%)respectively;in winter,dominant bacterial communities at 4 sampling points are the Deinococcus at BLQG(6.2%)and TJCR(8.97%)and the Gpl at YRBS(8.35%)and ZJGSUJC(6.19%);in spring,dominant bacterial communities are Streptophyta(19.24%)at BLQG,Streptophyta(31.07%)at TJCR,Buchnera(29.63%)at YRBS and Streptophyta(17.61%)at ZJGSUJC.According to the analysis on adiversity indexes,air-borne bacteria at YRBS in autumn are high in abundance and low in homogeneity,and that at BLQG in winter are low in abundance and high in homogeneity.(2)The concentrations of air microorganisms at 4 scenic spots in West Lake Scenic Area vary significantly.The maximum concentration of air-borne bacteria at MSBB is 961 CFU/m~3,and the minimum concentration at OSW is 193 CFU/m~3;the maximum concentration of air-borne fungi at MSBB is 668 CFU/m~3,and the minimum concentration at PSHFRC is 193 CFU/m~3;The concentrations of air-borne bacteria and fungi at different sampling points in summer are significantly higher than those in winter.The particle size distribution characteristics of air-borne bacteria and fungi at different sampling points are different greatly;the concentration percentage of air-borne bacterial particles at different sampling points is high in class I,and that of air-borne fungal particles is high in classes III and IV.The structures of air-borne bacterial communities at 4 scenic spots in West Lake Scenic Area vary greatly.There are totally 33 phyla and 954 genera of air-borne bacteria identified;from the perspective of phylum,high-content air-borne bacteria at different scenic spots include Proteobacteria,Actinobacteria,Firmicutes,Bacteroidetes and Cyanobacteria;from the perspective of genus,dominant bacterial communities at different scenic spots differ from one another,and high-content bacterial genera at MSBB,TPMM,OSW and PSHFRC are Massilia(6.22%),Janibacter(6.45%),Sphingomonas(6.05%)and Methylobacterium(11.5%)respectively.The OTU quantities at MSBB,TPMM,OSW and PSHFRC are 5075,4261,3771 and 4688 respectively.According to the analysis on a diversity indexes,air-borne bacteria at PSHFRC are low in abundance and high in homogeneity,while air-borne bacteria at MSBB are high in abundance and low in homogeneity.(3)Concentrations of air microorganisms at different heights vary greatly.The concentrations of air-borne bacteria and fungi decrease gradually with the increase in sampling height.The particle size of air-borne bacteria at different heights is of skewed distribution,and the percentages of bacterial communities of classes I to VI in samplers decrease gradually;the particle size of air-borne fungi is of lognormal distribution,and bacterial communities are mainly in classes Ⅲ and Ⅳ.There are totally 17 phyla and 296genera of air-borne bacteria identified at different heights;from the perspective of phylum,dominant bacterial communities at different heights are Proteobacteria;from the perspective of genus,bacterial communities vary with the change in heights;the relative content of bacterial community Gpl rises with the increase in height,and that of Clostridium reduces with the increase in height.The OTU quantities at low(L),medium(M)and high(H)layers are 3358,2894 and 2143 respectively.According to the analysis on a diversity indexes,air-borne bacteria at the high layer are low in abundance and high in homogeneity,while air-borne bacteria at the low layer are high in abundance and low in homogeneity.(4)There are totally 22phyla and 588genera of air-borne bacteria identified in different weathers,and they vary greatly.From the perspective of phylum level,bacterial communities with highest content in fine weather are Firmicutes(46.56%),and dominant bacterial communities in other weathers are Proteobacteria,accounting for 35.44%,41.45%and 38.44%in cloudy,rainy and hazy weathers respectively;from the perspective of genus level,dominant bacterial communities in sunny,cloudy,rainy and hazy weathers are Lactobacillus(18.13%),Mucilaginibacter(5.2%),Streptococcus(8.11%)and GpI(6.59%)respectively.The OTU quantities of air-borne bacteria in sunny,cloudy,rainy and hazy weathers are 1575,1745,1483 and 2185 respectively.According to the analysis on a diversity indexes,air-borne bacteria in hazy weather are high in abundance and low in homogeneity.(5)The concentrations of air-borne bacteria and fungi are significantly related to pollution factors and have a notable negative correlation with air quality index,O3 concentration and PM 10 concentration;the concentration of air-borne bacteria has a notable positive correlation with NO2 concentration and PM2.5 concentration,and the concentration of air-borne fungi has a notable positive correlation with NO2 concentration,CO concentration and PM2.5 concentration.The 16SrDNA gene copy number of air-borne bacteria before and after the extreme high-temperature weather varies significantly in 4 functional zones in Hangzhou City.Before the extreme high temperature,the gene copy numbers at YRBS,BLQG,ZJGSUJC and TJCR are 9.50 10~3/m~3,3.98 10~3/m~3,1.17 10~4/m~3 and 6.46 10~4/m~3 respectively;after the extreme high temperature,the 16SrDNA gene copy numbers are 4.38 10~2/m~3,0.31 10~2/m~3,1.54 10~3/m~3 andl.30 10~3/m~3 respectively;the reduction magnitudes are about 95%,99%,87%and 80%respectively.Before and after the extreme high temperature,microbial community structures in 4 different functional zones in Hangzhou City vary significantly;dominant bacterial communities before the high temperature are Caulobacterales(17.9%),Actinomycetes(17.7%),Burkholderiales(10.9%),Rhizobiales(8.9%),Sphingomonadales(7.7%)and Rhodocyclales(6.9%);dominant bacterial communities after the high temperature include Rhodocyclales(29.9%),Burkholderiales(19.9%),Actinomycetes(13.9%)and Bacillales(7.6%).After experiencing the extreme high-temperature weather,Burkholderiales,Rhodocyclalesand Bacillales increase significantly in their relative contents,while Actinomycetes,Caulobacterales,Rhizobiales,Sphingomonadales and Xanthomonadales decrease significantly in their relative contents.