City microbes are finding surprising new ways to survive

After a seemingly endless pandemic, we’ve all become a tad obsessed with scrubbing, sanitizing, and disinfecting our urban environments. But as we buckle up and venture into the new normal, a lingering question remains – are we inadvertently rearranging the microbes in cities?

In an intriguing new study, scientists have unveiled some fascinating insights into how our daily behaviors are altering the microbial ecosystem in our homes, offices, and public spaces.

City zone of microbes

“Built environments offer distinct conditions that set them apart from natural and engineered habitats,” said Dr. Xinzhao Tong, an assistant professor at Xi’an Jiaotong-Liverpool University (XJTLU), China, and lead author of the study.

“Areas with many buildings are low in the traditional nutrients and essential resources microbes need for survival, so these built environments have a unique microbiome.”

Dr. Tong explained that our use of cleaning and other manufactured products creates a unique setting that puts selective pressures on microbes, which they must adapt to or be eliminated.

However, noted Dr. Tong, the mechanisms by which microbes adapt and survive in built environments are poorly understood.

Unique census of city microbes

Our cities teem with life that’s invisible to the naked eye, notably within the urban microbiome. Dr. Tong and her team performed a unique census of these unseen citizens.

The researchers collected 738 samples from a range of built environments in Hong Kong – from public facilities and residences to subways, piers, and even human skin.

The analysis yielded astounding results – 363 never-before-identified microbial strains co-habiting our skin and surroundings. Some of them even possessed genes that allow them to consume city-specific products as a source of energy.

City microbes utilizing limited resources

One resilient strain was originally spotted in the harsh desert soils of Antarctica and can now be found chomping down ammonium ions in cleaning products.

“The genome of this novel strain of Eremiobacterota enables it to metabolize ammonium ions found in cleaning products. The strain also has genes for alcohol and aldehyde dehydrogenases to break down residual alcohol found in common disinfectants,” said Dr. Tong.

“Microbes possessing enhanced capabilities to utilize limited resources and tolerate manufactured products, such as disinfectants and metals, out-compete non-resistant strains, enhancing their survival and even evolution within built environments. They could, therefore, pose health risks if they are pathogenic.”

Diverse strains of city microbes

Not all of our microscopic co-dwellers are welcome guests. Among the newly identified strains were 11 unique incarnations of Micrococcus luteus. This type of bacteria is typically harmless to humans, but capable of causing adverse reactions in individuals with weakened immune systems.

While some bacteria adapt to become resistant to our cleaning practices, others have taken a different survival route.

Meet the “nanobacteria” – tiny, enigmatic bacteria with minuscule genomes that lack the resources to fend for themselves.

Symbiotic relationship with humans

Within these, the researchers found a strain that had evolved a symbiotic relationship with its human host, producing vital antioxidant compounds in return for shelter and sustenance.

“Some strains of Patescibacteria are considered parasitic as they rely on bacterial hosts to supply their nutrients. However, in this study, the researchers found that one of the nanobacteria strains, recovered from human skin, contains genes for the biosynthesis of carotenoids and ubiquinone,” noted Dr. Tong.

“These antioxidant compounds are vital to humans, and we typically acquire them, especially carotenoids, through our diets, suggesting a possible mutualistic relationship between bacteria and us as their hosts.”

Dynamic changes in city microbes

An insightful exploration into the microbial compositions of urban environments reveals a symphony of interactions that extend beyond mere existence. These tiny organisms are constantly communicating, competing, and cooperating in ways that intricately influence their surroundings.

The cityscape acts as both an orchestra and a battleground where genetic exchanges enhance survival capabilities amidst diverse conditions. By analyzing microbial DNA, researchers can trace these interactions, shedding light on how urban ecosystems foster microbial coexistence and resilience.

This evolving knowledge not only enriches our understanding of microbial ecology but also holds the potential to inform public health strategies by recognizing microbial patterns that could influence epidemic dynamics.

Future research directions

Despite remarkable scientific advancements, significant gaps remain in our comprehension of urban microbiomes and their broader implications on human health and environmental stability.

Dr. Tong and her colleagues emphasize the need for cross-disciplinary collaboration, blending fields like microbiology, urban planning, and public health to create a cohesive landscape of understanding.

By aligning scientific inquiry with public education initiatives, we can empower communities to make informed decisions that support both microbial diversity and human health.

As researchers know more on the microbes of our cities, they envisage a future where urban living can harmoniously integrate with a flourishing microbial biosphere, ultimately promoting a healthier, more sustainable coexistence.

Building a microbial blueprint

This expansive study, exploring how microbes adapt and thrive in our built environments, could help devise better strategies for cultivating a beneficial microbial ecosystem indoors.

The research team is now investigating the evolution of resistance in pathogenic microbes within intensive care units, with the aim of enhancing infection control practices and safeguarding the health of healthcare workers and patients.

In essence, it’s about striking a balance, where we can co-exist with our microbial friends in our cityscapes, learning from each other, and evolving together for a healthier future.

The study is published in the journal Microbiome.

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