Letting The Sunshine In

House dust contains a myriad of bacteria – what can we do to help?

We’re surrounded! House dust is a rich source of bacteria

https://phys.org/news/2008-04-house-rich-source-bacteria.html

“If you’ve always suspected there are unknown things living in the dark and dusty corners of your home and office, we are now one step closer to cataloging exactly what might be lurking in your indoor environment. Buildings have their own pattern of bacteria in indoor dust, which includes species normally found in the human gut, according research published in BMC Microbiology.

The microbial flora from indoor dust samples from two buildings was complex and dominated by bacterial groups originating from users of the buildings. The Finnish-based research team investigated the species level diversity and seasonal dynamics of bacterial flora in indoor dust by sequencing DNA from the dust samples collected.

“People spend most of their lives in different indoor environments: homes, schools, workplaces” explained microbiologist and lead researcher Helena Rintala. “And as such we are constantly challenged by airborne microbes. It is important then to understand the exact nature of this exposure and to be able to understand how it affects our health.”

Indoor dust samples were taken in 2003 from two nursing homes located in small towns in central Finland, 100 km apart. Both buildings were similar in age, building frame, ventilation, use and rural location. Offices in the two buildings were sampled at different times during 1 year to obtain four samples per building, one for each season

By examining dust samples taken from hard surfaces such as tables and floors using a vacuum cleaner, Rintala and her colleagues found that Gram-positive bacteria dominated. This group includes Staphylococcus and Streptococcus species that belong to the normal bacteria in humans. Approximately five hundred bacterial species were estimated to be present in the dust, which is relatively easy to collect and reveals a good picture of the total microbial exposure in indoor environments. Although the diversity of the bacteria differed according to seasons, the difference between the buildings was greater than the variation observed throughout the year within a particular building.

“So far most of our information about microbes in indoor environments has concentrated on fungi. Our results show basic information on bacteria. Although our findings are significant, we do need more research to find out where the microbes are coming from for instance, “ concluded Rintala.

Source: BioMed Central”

Letting the sunshine in may kill dust-dwelling bacteria

Letting the sunshine in may kill dust-dwelling bacteria
by BioMed Central

https://phys.org/news/2018-10-sunshine-dust-dwelling-bacteria.html

“Allowing sunlight in through windows can kill bacteria that live in dust, according to a study published in the open access journal Microbiome.

Researchers at the University of Oregon found that in dark rooms 12% of bacteria on average were alive and able to reproduce (viable). In comparison only 6.8% of bacteria exposed to daylight and 6.1% of bacteria exposed to UV light were viable.

Dr. Fahimipour said: “Humans spend most of their time indoors, where exposure to dust particles that carry a variety of bacteria, including pathogens that can make us sick, is unavoidable. Therefore, it is important to understand how features of the buildings we occupy influence dust ecosystems and how this could affect our health.”

Dust kept in the dark contained organisms closely related to species associated with respiratory diseases, which were largely absent in dust exposed to daylight.

The authors found that a smaller proportion of human skin-derived bacteria and a larger proportion of outdoor air-derived bacteria lived in dust exposed to light that in than in dust not exposed to light. This may suggest that daylight causes the microbiome of indoor dust to more strongly resemble bacterial communities found outdoors.

The researchers made eleven identical climate-controlled miniature rooms that mimicked real buildings and seeded them with dust collected in residential homes. The authors applied one of three glazing treatments to the windows of the rooms, so that they transmitted visible, ultraviolet or no light. After 90 days, the authors collected dust from each environment and analysed the composition, abundance, and viability of the bacteria present.

Dr. Fahimipour said: “Our study supports a century-old folk wisdom, that daylight has the potential to kill microbes on dust particles, but we need more research to understand the underlying causes of shifts in the dust microbiome following light exposure. We hope that with further understanding, we could design access to daylight in buildings such as schools, offices, hospitals and homes in ways that reduce the risk of dust-borne infections.”

The authors caution that the miniature room environments used in the study were exposed to only a relatively narrow range of light dosages. Although the researchers selected light dosages similar to those found in most buildings, there are many architectural and geographical features that produce lower or higher dosages of light that may need additional study.”

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