Abstract
BackgroundThe study of the microbial communities in the built environment is of critical importance as humans spend the majority of their time indoors. While the microorganisms in living spaces, especially those in the air, can impact health and well-being, little is known of their identity and the processes that determine their assembly. We investigated the source-sink relationships of airborne bacteria in 29 homes in the San Francisco Bay Area. Samples taken in the sites expected to be source habitats for indoor air microbes were analyzed by 16S rRNA-based pyrosequencing and quantitative PCR. The community composition was related to the characteristics of the household collected at the time of sampling, including the number of residents and pets, activity levels, frequency of cooking and vacuum cleaning, extent of natural ventilation, and abundance and type of vegetation surrounding the building.ResultsIndoor air harbored a diverse bacterial community dominated by Diaphorobacter sp., Propionibacterium sp., Sphingomonas sp., and Alicyclobacillus sp. Source-sink analysis suggested that outdoor air was the primary source of indoor air microbes in most homes. Bacterial phylogenetic diversity and relative abundance in indoor air did not differ statistically from that in outdoor air. Moreover, the abundance of bacteria in outdoor air was positively correlated with that in indoor air, as would be expected if outdoor air was the main contributor to the bacterial community in indoor bioaerosols. The number of residents, presence of pets, and local tap water also influenced the diversity and size of indoor air microbes. The bacterial load in air increased with the number of residents, activity, and frequency of natural ventilation, and the proportion of bacteria putatively derived from skin increased with the number of residents. Vacuum cleaning increased the signature of pet- and floor-derived bacteria in indoor air, while the frequency of natural ventilation decreased the relative abundance of tap water-derived microorganisms in air.ConclusionsIndoor air in residences harbors a diverse bacterial community originating from both outdoor and indoor sources and is strongly influenced by household characteristics.Electronic supplementary materialThe online version of this article (doi:10.1186/s40168-015-0128-z) contains supplementary material, which is available to authorized users.
Highlights
The study of the microbial communities in the built environment is of critical importance as humans spend the majority of their time indoors
The most represented operational taxonomic units (OTUs) we found in indoor air samples are taxonomically related with microorganisms that are ubiquitous in nature and previously encountered in soil, sediments, water and in association with plants, including Diaphorobacter (10 % in indoor air), Alicyclobacillus (6 %), Methylobacterium (4 %), Sphingomonas (4 %), Hymenobacter (2 %), Pseudomonas (2 %), and Roseomonas (1 %) (Additional file 2: Table S2 and references therein)
Sequences affiliated with Propionibacterium (12 % in indoor air), representative genus of the family Propionibacteriaceae, were in the highest proportion in outdoor air, skin, pets, carpet, bathtub tiles, and tap water samples
Summary
The study of the microbial communities in the built environment is of critical importance as humans spend the majority of their time indoors. The study of the indoor microbiome (the microbial communities of the built environment) is of critical importance since humans spend the majority of their time indoors and regularly encounter microbes in this habitat. Microbes, including those present in indoor spaces, impact human health and well-being [1, 2]. The variation in environmental conditions within buildings (such as humidity, temperature, and availability of nutrients), the intensity or legacy of human usage (e.g., cleaning patterns), and the variation in possible source habitats (e.g., human numbers and features, pets, plants, food, and tap water) are likely to shape the indoor microbiome creating microhabitats colonized by distinct microbial communities
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
