Sink drains and plumbing are usually unpleasant places, at least from a human perspective.
If you’re a fungus, however, you may feel differently. In fact, one of the reasons we’re often repelled by sinks — along with dirty sponges and other sink accessories — is precisely because they’re such great habitats for unsavory microbes.
In a new study by researchers from the University of Reading and the UK Center for Ecology and Hydrology, scientists have taken a deep dive into this murky ecosystem, investigating more than 250 “toilet sink fungal communities”. on a university campus.
Led by University of Reading bioinformatician Soon Gweon, the research team collected samples of toilet sink drains and P-traps from 20 buildings on the university’s main campus.
The researchers used sterile cotton swabs to take samples from the drains and P-traps, recording details about the qualities of each sink, including its location, purpose, gender label for bathrooms, and whether the water flowing down the drain was hot or cold. Extracting DNA from the samples, they used polymerase chain reaction (PCR) amplification and bioinformatics processing to help identify the microbial residents of the wells.
The results showed moldy jungles of fungal diversity, like tiny rainforests in the drains.
It may seem obvious that moist places like these would promote microbial life, but the mere presence of fungi is not the main benefit. These fungal communities are diverse, the researchers report, but also incredibly similar to each other.
The pits housed 375 genera of fungi – the taxonomic rank above species – from a range of classes, orders and families. The study found fungi representing seven different phyla, the taxonomic rank below the kingdom.
Despite high biodiversity in each well, all fungal communities showed surprisingly similar taxonomic profiles, the researchers report, meaning that the list and ratio of fungi did not vary much from well to well, or even from one building to another.
The researchers note that they are not sure what drives this similarity, but note that the similarity of fungus from sinks in different restrooms and buildings could reflect “similar use” by members of the community.
All of these sinks are primarily used for hand washing, with many of those using the facilities being from the wider university population, and any of them could be exposed to germs when using the sinks.
“We spend 90% of our time indoors, so we are exposed to fungus in our homes and workplaces,” says Gweon.
“For most people this is not a problem, but for those who are immunocompromised, certain fungal species can cause serious infections.”
The study suggests that sink drains and P-traps are not only nice places for microbes, but could serve as reservoirs for certain molds, yeasts and other fungi, harboring and potentially helping to spread species that can make humans sick.
“It’s no big surprise to find fungi in a warm, humid environment. But P-wells and traps have so far been overlooked as potential reservoirs of these microorganisms,” Gweon says.
“This could be a very important finding for those trying to help immunocompromised people avoid infections with some of the opportunistic pathogens that can lurk in sinks, such as Fusarium.”
Drains and sink pipes provide a unique habitat for fungi in the built environment, note Gweon and colleagues, thanks to continuous humidity, temporary temperature changes, high detergent pH and buildup. potential organic matter.
However, fungi in sinks must also be resistant. They deal with blasts of hot water, for example, as well as varying acidity levels and food availability. Some fungi could exploit the detergents in soap as a carbon-rich food source, the researchers suggest.
The most abundant and ubiquitous genus found in the new study was Exophialareport the researchers, a “black yeast” that includes terrestrial and aquatic species.
“Exophiala species can be considered opportunistic pathogens causing skin and superficial infections,” they write. These may not be high risk overall, but “fatal systemic infections have been documented.”
The study was published in Environmental DNA.
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