by Mechas
Image by Mechas
There is no doubt that our understanding of microbiomes – those microbial communities in practically any environment – has increased in recent years. Research now covers almost any conceivable niches, from cow rumen or the human gut, to numerous human-made ecosystems.
One such ecosystem is the built environment. Humans transitioned over millennia from rural to urban areas where we now spend most of our time indoors in what we call built environments. Since the beginning of this century most humans reside in cities. While the ensuing lifestyle changes have obvious benefits and improve the quality of life, they also mean that we changed how we interact with our surroundings, which includes not only other people, but also animals and the environment. These three aspects of our interconnected ecosystems, humans, animals and the environment impact one another, as recognized by the One Health concept. This also means that changes to the natural landscape driven by construction of urban centers inevitably alter the microbial communities around us. What we are slowly realizing is that these microbiomes, in turn, are also critical to our overall well-being.
Unraveling the connections between built environment microbiomes and health is not easy. However, there are some cases that clearly illustrate the impact of urban living and built-environment microbiomes on human health. One example was the rapid spread of the SARS-CoV2 virus that resulted in the recent COVID-19 pandemic. Another example is provided by the spread of antimicrobial resistant pathogens in hospitals. The rise in bacteria resistant to antimicrobials continually frustrates efforts for control and led to a global antimicrobial resistance crisis that results in millions of deaths each year. In other cases, the loss of microbial diversity in urban centers and the reduced exposure to potentially beneficial environmental microbes are linked to chronic illnesses particularly prevalent in industrialized societies, such as allergies and asthma.
The built environment ecosystems are, as you would expect, far from sterile. They are populated by complex microbial assemblages that include viruses, bacteria, fungi, protozoa and even microscopic animals. These are sourced from an incoming pool of organisms capable of colonizing these spaces, but only those that survive or proliferate under local conditions, such as pathogens that withstand conditions in a hospital intensive care unit for example, will remain. Humans and animal occupants, such as pets, rodents and insects, vegetation and external elements like dust particles provide much of the microbial input for these indoor spaces.
Many studies have focused on humans and how they interact and exchange microbes with their built environments. We carry and transport our own "microbial cloud" to the places we visit and therefore we unwittingly participate in seeding local surfaces with our own microbes. Not surprisingly, a built environment microbiome will reflect those of its human occupants. For example, daycare centers and homes differ in the distribution of yeast and filamentous fungi. This is also why some recent studies focused on describing urban microbiomes using as proxy microbial communities in mass-transit systems. Such daily interactions, nowadays mostly within constructed spaces, also means that we pick up different microbes from our surroundings. We therefore not only provide microbes as input for built environment microbiomes but are also influenced by them.
The realization that microbes in built environments, and in any environment really, are closely connected with human health is a real eye opener. These microbiomes are inevitable and essential and, therefore, critical when it comes to planning healthy buildings and urban spaces. Some ideas to promote healthier living conditions include rewilding of urban areas – restoring them to a more natural state – and considering microbes and their ecology – how they relate to other organisms and their environment – when designing built environments.
We are deeply connected with our surrounding microbes. Understanding how these microbial partners affect our well-being, be they specific members or whole communities, will require further studies. Hopefully, multidisciplinary teams capable of addressing environment-human-microbial interactions will integrate this knowledge in the design of future sustainable and healthier places to live in.
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