Comparison Of House Dust Microbiome Profiles In Different Urbanization Level Areas

BackgroundUrbanization definitely plays a predominant role in the development of asthma and allergy.Several studies have revealed that children living on farms or having regular contact to farms have less asthma and atopy than children living in urban environments.People spend most of their time inside buildings and the indoor microbiome is a major part of our everyday environment.It affects human's well-being and therefore its composition is important for impacting directly on human health outcomes.House dust is a complex mixture of inorganic and organic material with microbes in abundance.Environmental exposure to microbes and their components has long been linked to numerous non-infectious health effects,both beneficial and detrimental,in children and adults.ObjectiveTo compare the composition and diversity of bacterial microbiome in house dust in areas with different urbanization level,and investigate the effect of occupant number,pet number and their duration kept in the household and urbanization levels on the house dust microbiome.MethodsQuestionnaire was used to investigate the prevalence of adult asthma and allergic disease in China.House dust samples were collected with two methods:settled dust?SD?was collected from surfaces above floor level with a medical cotton and floor dust?FD?was collected with a vacuum machine.SD samples were collected in the rural?Xinxiang rural area,XR,n=74?and urban areas?Xinxiang urban area,XU,n=33,Zhengzhou urban area,ZU,n=32?in Central China.FD samples were collected in Australia?AU,n=58?.The samples were collected in July and August 2017 in China and December 2017 and January 2018 in Australia.The average indoor temperature was 27°C,and average indoor relative humidity was 42%.Concurrently,the number of occupants,the number of pets and the duration of pet kept in the house were recorded for all samples in Australia,then the samples from Australia was divided into AUP?the sampling house with pets?and AUNP?the sampling house without pets?.In addition,the urbanization level was also classified according to the urban population proportion and gross domestic product using the city classification of the Globalization and World Cities Research Network in 2018.SD and FD samples were stored in foil paper at-80°C until analysis.DNA was extracted from SD and FD samples of 250mg weighted dried fine dust using the cetyltrimethylammonium ammonium bromide?CTAB?method.High-throughput sequencing of 16s rDNA was employed to profile house dust bacterial communities.Results1.The detection rate of asthma in rural and suburban areas showed significant difference?P=0.024?.2.XR had the highest occupant number but the lowest urbanization level.However,AU had the lowest occupant number but the highest urbanization level.3.Phylum-level taxonomical assignment showed that Proteobacteria and Actinobacteria were dominant in SD samples:XR?47.62%,15.17%?,XU?46.92%,18.76%?and ZU samples?40.80%,19.04%?.While in FD samples,Proteobacteria,Firmicutes and Actinobacteria were the most abundant phyla bacteria,with AUP?43.06%,19.46%,and16.17%?,AUNP?35.78%,20.85%,and 20.09%?.At the genus level,unidentified_Mitochondria?5.71%?,Sphingomonas?8.27%?,unidentified_Chloroplast?16.29%?and Staphylococcus?8.80%?were the most common genera in XR,XU,ZU and AU samples,respectively.4.XR dust had higher bacterial richness and diversity than other groups in SD.There were no significant difference about the bacterial richness and diversity between AUP and AUNP.5.House dust bacterial community structure had higher similarity in the group XU,ZU and AU,respectively.While that of XR had lower similarity.6.In SD samples,areas with higher urbanization level had higher relative abundance in the pathway metabolism.7.Some house dust bacterial phyla and genera,with a relative abundance larger than 1%,presented significant associations with environmental factors?the number of occupant,pet number and their duration kept in the household,the urbanization level?.8.The environmental factors including URB?r²=0.741 P<0.001?,the occupant number?r²=0.311 P<0.001?,petN?r²=0.550 P<0.001?and petY?r²=0.517 P<0.001?had significant correlation with the distribution of house dust bacterial community.9.Bacterial phyla Firmicutes,Fusobacteria,Gemmatimonadetes,Verrucomicrobia and bacterial genera Staphylococcus,Pseudomonas,Corynebacterium₁,Bartonella,and Streptococcus were strongly correlated with the urbanization level.ConclusionsThere was a significant difference in the house dust microbiome among different urbanization level areas.Areas with the lower urbanization level had higher bacterial richness and diversity of house dust.Occupant,pet and urbanization level were significant correlated with some of the house dust microbiome.The correlation between urbanization level and the distribution of house dust microbiome was stronger than the other environmental factors.