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The diversity and distribution of fungi on residential surfaces.

Adams RI, Miletto M, Taylor JW, Bruns TD - PLoS ONE (2013)

Bottom Line: Sampling was done in replicated units of a university-housing complex without reported mold problems, and sequences were analyzed using both QIIME and the new UPARSE approach to OTU-binning, to the same result.Overall, fungal richness across indoor surfaces was high, but based on known autecologies, most of these fungi were unlikely to be growing on surfaces.We conclude that while some endogenous fungal growth on typical household surfaces does occur, particularly on drains and skin, all residential surfaces appear - to varying degrees - to be passive collectors of airborne fungi of putative outdoor origin, a view of the origins of the indoor microbiome quite different from bacteria.

View Article: PubMed Central - PubMed

Affiliation: Plant & Microbial Biology, University of California, Berkeley, California, United States of America.

ABSTRACT
The predominant hypothesis regarding the composition of microbial assemblages in indoor environments is that fungal assemblages are structured by outdoor air with a moderate contribution by surface growth, whereas indoor bacterial assemblages represent a mixture of bacteria entered from outdoor air, shed by building inhabitants, and grown on surfaces. To test the fungal aspect of this hypothesis, we sampled fungi from three surface types likely to support growth and therefore possible contributors of fungi to indoor air: drains in kitchens and bathrooms, sills beneath condensation-prone windows, and skin of human inhabitants. Sampling was done in replicated units of a university-housing complex without reported mold problems, and sequences were analyzed using both QIIME and the new UPARSE approach to OTU-binning, to the same result. Surfaces demonstrated a mycological profile similar to that of outdoor air from the same locality, and assemblages clustered by surface type. "Weedy" genera typical of indoor air, such as Cladosporium and Cryptococcus, were abundant on sills, as were a diverse set of fungi of likely outdoor origin. Drains supported more depauperate assemblages than the other surfaces and contained thermotolerant genera such as Exophiala, Candida, and Fusarium. Most surprising was the composition detected on residents' foreheads. In addition to harboring Malassezia, a known human commensal, skin also possessed a surprising richness of non-resident fungi, including plant pathogens such as ergot (Claviceps purperea). Overall, fungal richness across indoor surfaces was high, but based on known autecologies, most of these fungi were unlikely to be growing on surfaces. We conclude that while some endogenous fungal growth on typical household surfaces does occur, particularly on drains and skin, all residential surfaces appear - to varying degrees - to be passive collectors of airborne fungi of putative outdoor origin, a view of the origins of the indoor microbiome quite different from bacteria.

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The Study Sites for Surveying Fungi in Residential Units of a University Housing Complex.Pictured are three surface types on what cotton-tipped swabs collected material for fungal analysis. Biofilms were collected on three types of drains: kitchen sinks (A), bathroom sinks (B), and bathtub drains. From the upward-facing edge of windowsills in kitchens, living rooms, bedrooms (C), and bathrooms, dust was also collected. Skin samples were taken from the forehead (D). Fungi on these surfaces were compared with each other and with passively settled indoor and outdoor dust from the same sampling locality [10].
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pone-0078866-g001: The Study Sites for Surveying Fungi in Residential Units of a University Housing Complex.Pictured are three surface types on what cotton-tipped swabs collected material for fungal analysis. Biofilms were collected on three types of drains: kitchen sinks (A), bathroom sinks (B), and bathtub drains. From the upward-facing edge of windowsills in kitchens, living rooms, bedrooms (C), and bathrooms, dust was also collected. Skin samples were taken from the forehead (D). Fungi on these surfaces were compared with each other and with passively settled indoor and outdoor dust from the same sampling locality [10].

Mentions: We sampled areas of potential fungal growth in areas of a residence that are open to the living space, not regions hidden behind walls: drains in the kitchen sink, bathroom sink, and bathtub; the lower upward-facing edge of windowsills in the kitchen, living room, bedroom, and bathroom; and the foreheads of all residents of the unit (Figure 1). Sampling was replicated in 11 units of a university housing complex, in which all residences have identical construction materials and similar floor plans and which does not allow cats or dogs, as previously described [10]. To sample surfaces, sterile, nucleotide-free water was used to moisten a cotton swab, and the surface was rubbed for 5−10 seconds. We did not observe any visible fungal growth in these residences outside of drains. Swabs from home surfaces were stored in individual glass vials except for the forehead swabs, which were pooled for all residents of a unit to protect volunteer confidentiality. Swabs were stored frozen at −80 °C until nucleotide extraction. Additionally, residents completed a survey on the characteristics and typical use of their unit to provide information on: the number of bedrooms, bathrooms, and residents, the age of the unit, the presence of houseplant(s) and the use of a humidifier. Other parameters (frequency of cooking, cleaning, occupancy, and window opening) were invariable and therefore excluded from the analysis. Swab surveys were conducted twice, once in August 2011 in 11 units and again in January 2012 for 8 of those same units. The sampling protocol was regulated by the University of California’s Committee for the Protection of Human Subjects, Protocol ID #2011-03-2947, and approved by both the Village Residents Association for the housing complex on May 18, 2011 and the Residential and Student Service Programs of the University on July 25, 2011.


The diversity and distribution of fungi on residential surfaces.

Adams RI, Miletto M, Taylor JW, Bruns TD - PLoS ONE (2013)

The Study Sites for Surveying Fungi in Residential Units of a University Housing Complex.Pictured are three surface types on what cotton-tipped swabs collected material for fungal analysis. Biofilms were collected on three types of drains: kitchen sinks (A), bathroom sinks (B), and bathtub drains. From the upward-facing edge of windowsills in kitchens, living rooms, bedrooms (C), and bathrooms, dust was also collected. Skin samples were taken from the forehead (D). Fungi on these surfaces were compared with each other and with passively settled indoor and outdoor dust from the same sampling locality [10].
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3815347&req=5

pone-0078866-g001: The Study Sites for Surveying Fungi in Residential Units of a University Housing Complex.Pictured are three surface types on what cotton-tipped swabs collected material for fungal analysis. Biofilms were collected on three types of drains: kitchen sinks (A), bathroom sinks (B), and bathtub drains. From the upward-facing edge of windowsills in kitchens, living rooms, bedrooms (C), and bathrooms, dust was also collected. Skin samples were taken from the forehead (D). Fungi on these surfaces were compared with each other and with passively settled indoor and outdoor dust from the same sampling locality [10].
Mentions: We sampled areas of potential fungal growth in areas of a residence that are open to the living space, not regions hidden behind walls: drains in the kitchen sink, bathroom sink, and bathtub; the lower upward-facing edge of windowsills in the kitchen, living room, bedroom, and bathroom; and the foreheads of all residents of the unit (Figure 1). Sampling was replicated in 11 units of a university housing complex, in which all residences have identical construction materials and similar floor plans and which does not allow cats or dogs, as previously described [10]. To sample surfaces, sterile, nucleotide-free water was used to moisten a cotton swab, and the surface was rubbed for 5−10 seconds. We did not observe any visible fungal growth in these residences outside of drains. Swabs from home surfaces were stored in individual glass vials except for the forehead swabs, which were pooled for all residents of a unit to protect volunteer confidentiality. Swabs were stored frozen at −80 °C until nucleotide extraction. Additionally, residents completed a survey on the characteristics and typical use of their unit to provide information on: the number of bedrooms, bathrooms, and residents, the age of the unit, the presence of houseplant(s) and the use of a humidifier. Other parameters (frequency of cooking, cleaning, occupancy, and window opening) were invariable and therefore excluded from the analysis. Swab surveys were conducted twice, once in August 2011 in 11 units and again in January 2012 for 8 of those same units. The sampling protocol was regulated by the University of California’s Committee for the Protection of Human Subjects, Protocol ID #2011-03-2947, and approved by both the Village Residents Association for the housing complex on May 18, 2011 and the Residential and Student Service Programs of the University on July 25, 2011.

Bottom Line: Sampling was done in replicated units of a university-housing complex without reported mold problems, and sequences were analyzed using both QIIME and the new UPARSE approach to OTU-binning, to the same result.Overall, fungal richness across indoor surfaces was high, but based on known autecologies, most of these fungi were unlikely to be growing on surfaces.We conclude that while some endogenous fungal growth on typical household surfaces does occur, particularly on drains and skin, all residential surfaces appear - to varying degrees - to be passive collectors of airborne fungi of putative outdoor origin, a view of the origins of the indoor microbiome quite different from bacteria.

View Article: PubMed Central - PubMed

Affiliation: Plant & Microbial Biology, University of California, Berkeley, California, United States of America.

ABSTRACT
The predominant hypothesis regarding the composition of microbial assemblages in indoor environments is that fungal assemblages are structured by outdoor air with a moderate contribution by surface growth, whereas indoor bacterial assemblages represent a mixture of bacteria entered from outdoor air, shed by building inhabitants, and grown on surfaces. To test the fungal aspect of this hypothesis, we sampled fungi from three surface types likely to support growth and therefore possible contributors of fungi to indoor air: drains in kitchens and bathrooms, sills beneath condensation-prone windows, and skin of human inhabitants. Sampling was done in replicated units of a university-housing complex without reported mold problems, and sequences were analyzed using both QIIME and the new UPARSE approach to OTU-binning, to the same result. Surfaces demonstrated a mycological profile similar to that of outdoor air from the same locality, and assemblages clustered by surface type. "Weedy" genera typical of indoor air, such as Cladosporium and Cryptococcus, were abundant on sills, as were a diverse set of fungi of likely outdoor origin. Drains supported more depauperate assemblages than the other surfaces and contained thermotolerant genera such as Exophiala, Candida, and Fusarium. Most surprising was the composition detected on residents' foreheads. In addition to harboring Malassezia, a known human commensal, skin also possessed a surprising richness of non-resident fungi, including plant pathogens such as ergot (Claviceps purperea). Overall, fungal richness across indoor surfaces was high, but based on known autecologies, most of these fungi were unlikely to be growing on surfaces. We conclude that while some endogenous fungal growth on typical household surfaces does occur, particularly on drains and skin, all residential surfaces appear - to varying degrees - to be passive collectors of airborne fungi of putative outdoor origin, a view of the origins of the indoor microbiome quite different from bacteria.

Show MeSH
Related in: MedlinePlus