\n<\/p>\n
The natural world teems with microorganisms. Billions of species of bacteria, archaea, viruses and fungi make up complex ecosystems in the soil, water and air. The activity of these microbes sustains plants through their roots, animals through their guts and skin, and helps to regulate the planet\u2019s climate and chemical cycles.<\/p>\n
But people spend about 90% of their time indoors, sealed inside environments that are, by design, hostile to many microbes.<\/p>\n
A 3D computer image of a vertical garden that could surround a repurposed concrete water tower in Cairo.<\/span>Credit: Karim Moussa<\/span><\/p>\n The sterile nature of modern architecture offers a certain amount of protection from infectious diseases. But some scientists think that it contributes to the development of other maladies, particularly those related to the immune system. And they are exploring whether the built environment can be turned probiotic, providing exposure to a diverse set of beneficial microbes indoors.<\/p>\n The proposed interior of a repurposed water tower in Cairo.<\/span>Credit: Karim Moussa<\/span><\/p>\n Probiotic architecture means \u201cwe can target harmful microbes, but at the same time we still allow other benign microbes \u2014 or even potentially the microbes that are good for us \u2014 to exist\u201d, says Richard Beckett, an architect specializing in bioaugmented design at University College London. \u201cIt\u2019s recalibrating the idea that sterility is safest for our built environments.\u201d<\/p>\n But using homes, offices and schools as vectors for engineered exposure to microbes is controversial. Scientists are still learning which microbes can, and do, live indoors, and it\u2019s not clear which ones to introduce \u2014 or how to do so in a way that would be safe and effective.<\/p>\n People in the Amish community are regularly exposed to microbes through milking cows.<\/span>Credit: David Turnley\/Corbis\/VCG\/Getty<\/span><\/p>\n Most of the world\u2019s population lives in cities, and many people spend most of their days inside. A 2001 survey1 found that respondents in the United States spend 87% of their time inside sealed buildings, and a further 6% in vehicles.<\/p>\n The Casa de vidro (glass house) in Sao Paulo, Brazil, is surrounded by tropical vegetation.<\/span>Credit: Apolline Guillerot-Malick\/SOPA Images\/LightRocket\/Getty<\/span><\/p>\n The design of human structures, such as homes and offices, has been driven by a desire to keep humans isolated from animals, dirt and microbes. But scientists exploring probiotic indoor environments point to studies that suggest there are health benefits to mingling with microbes, particularly for young children.<\/p>\n The main living space of Casa da vidro overlooks trees, but the forest is kept outside \u2014 there is no balcony.<\/span>Credit: Apolline Guillerot-Malick\/SOPA Images\/LightRocket\/Getty<\/span><\/p>\n Exposure to dust, farm animals and their associated microbes can have a positive effect on children\u2019s immune systems. \u201cPeople who grow up on a farm have a 50% reduction in the likelihood of developing atopy,\u201d says Jack Gilbert, a paediatrician and microbiome researcher at the University of California, San Diego. Atopy, which causes people to overproduce certain kinds of antibody, can manifest as conditions such as asthma, dermatitis and food allergy.<\/p>\n Researchers Mark Fretz and Gwynne Mhuireach study the microbiomes of buildings at the University of Oregon, Eugene.<\/span>Credit: Celeste Noche for Nature<\/span><\/p>\n People in the Amish community in the United States and Canada farm much of their own food and often travel in horse-drawn vehicles, bringing them unusually close to animals, plants, soil and the microbes that they harbour. The prevalence of asthma among Amish schoolchildren is 5.2% (ref. 2) \u2014 lower than the US average of 8.1%. <\/p>\n If children\u2019s developing immune systems need exposure to environmental microbes \u2014 and if such exposures turn out to have benefits for adults, too \u2014 then urban dwellers will often miss out.<\/p>\n The Apartment (1960) depicts the emerging modern office as a sea of identical desks.<\/span>Credit: Pictorial Press Ltd\/Alamy<\/span><\/p>\n Modern architecture has been shaped partly by the desire to improve people\u2019s health. Avoidance of tuberculosis, in particular, drove design ideas from the mid-nineteenth and into the twentieth century. \u201cModernizing architecture was firstly a form of disinfection, a purification of buildings leading to a health-giving environment of light, air, cleanliness and smooth white surfaces without cracks or crevices where contagion might lurk,\u201d writes architectural historian Beatriz Colomina at Princeton University in New Jersey in The Architectural Review (see go.nature.com\/48r6vw0).<\/p>\n These strategies saved lives, but some architects and scientists argue that designing for cleanliness has gone too far.<\/p>\n In the early twentieth century, most buildings had windows that could be opened to let in fresh air. What\u2019s more, the horizontal area of each storey in a building \u2014 the \u2018floor plate\u2019 to architects \u2014 was small. Those two design conventions meant that people were never far from ventilation and natural light during the day.<\/p>\n That changed mid-century, says architect Mark Fretz, who is co-director of the Institute for Health in the Built Environment at the University of Oregon in Eugene. \u201cThe floor plates got very deep,\u201d he says \u2014 people in some office buildings can work all day away from any window. And those windows are not likely to be operable. As concern for conserving energy grew in the 1970s, architects began cutting off access to outside air to ensure efficient operation of heating and cooling systems. \u201cThis creates a sealed environment that\u2019s more synthetic and controlled by technical means,\u201d Fretz says. \u201cWe\u2019ve transitioned metaphorically from caves to spaceships.\u201d<\/p>\n These \u2018spaceships\u2019 are hostile to many microbes. Plastic, glass and metal surfaces are smooth and dry. There\u2019s nowhere for a soil microbe that ends up there to gain purchase, and nothing for them to eat or drink. Flooring, furniture and work surfaces can contain antimicrobial chemicals, and those that don\u2019t are often regularly squirted with household cleaners containing these compounds.<\/p>\n \u201cWe can think of the built environment as a kind of extreme environment,\u201d says Erica Hartmann, who studies the microbiome of the built environment at Northwestern University in Evanston, Illinois.<\/p>\n Probiotic wall tiles are embedded with strains of Bacillis subtilis.<\/span>Credit: Richard Beckett\/Beckett Lab<\/span><\/p>\n With the exception of a handful of damp and relatively fertile niches, such as sink drains, microbial diversity is distinctly lower indoors than it is outside. Studies of household microbiomes have found that homes are populated mostly by microbes from the bodies of the people who live there \u2014 particularly those found on people\u2019s hands and feet, and in their noses \u2014 and from their pets. Rather than establishing themselves in the environment, these microbiomes are transient, and travel with a building\u2019s occupants. In one study3, for example, three families who moved house were found to take their indoor microbiome with them. One group even deposited it for a time in a hotel room that the family stayed in ahead of the move.<\/p>\n Colomina compares modern architecture to antibiotics. Just as the widespread use of these drugs has driven antibiotic resistance, architecture has \u201ccreated its own monsters\u201d, she writes in The Architectural Review. There is evidence that autoimmune diseases, allergies and metabolic diseases, such as obesity, are influenced by the microbes that people are exposed to, and that the diversity of these microbes is decreasing.<\/p>\n Architecture, she argues, should instead be more like the human gut: porous and diverse. But bringing the wild inside is easier said than done. Microbes and architecture can make an uneasy pairing, says Beckett. Architects try to design for permanence and stability, but microbes are \u201cunruly\u201d, he says. \u201cThey don\u2019t always behave.\u201d<\/p>\n A probiotic surface designed to host microbial communities in a building. <\/span>Richard Beckett\/Beckett Lab<\/span><\/p>\n One approach is to integrate environmental microbes into building materials. Beckett, who studied biochemistry and worked as a researcher at the UK pharmaceutical company GlaxoSmithKline before becoming an architect, hopes that benign microbiota incorporated into the built environment might outcompete or repel drug-resistant pathogens. Antimicrobial resistance is a major public-health concern, estimated4 to have been involved in nearly five million deaths in 2019.<\/p>\n To try to overcome this, Beckett has worked with microbiologists on a project called Niches for Organic Territories in Bio-Augmented Design (NOTBAD).<\/p>\n The NOTBAD team chose as its model pathogen a strain of methicillin-resistant Staphylococcus aureus (MRSA) that can repel many antibiotics and has become a scourge in hospitals. The team\u2019s benign microbes were strains of the soil bacterium Bacillus subtilis that have shown antimicrobial properties in the lab and can survive in dry indoor conditions.<\/p>\n The next task was choosing a material that could incorporate the benign microbes. Beckett\u2019s work draws on the concept of bioreceptivity: the ability of a material to be colonized by living organisms. This idea, which draws together materials science and ecology, reframes such colonization \u2014 moss or algae growing on a stone monument, for example \u2014 in a positive or neutral way, rather than viewing it as a destructive process. \u201cSome materials are receptive to microbial growth,\u201d says Beckett, and to him that isn\u2019t a bad thing.<\/p>\n Smooth materials that lack pores, such as glass, are generally not bioreceptive. Lab-made materials, such as squishy water-filled polymers called hydrogels, are very bioreceptive, but they\u2019re only available in small pieces, and are not durable enough for architectural use.<\/p>\n The NOTBAD team has explored several materials, including 3D printed plastics, aluminium and various formulations of concrete as a medium for B. subtilis. The team tested whether the microbes were viable in each material, then assessed whether the microbe\u2013material composite repelled MRSA.<\/p>\n A ceramic-based material performed best, inhibiting growth of the pathogen. The material is relatively sturdy and has rough surfaces and pores that can hold moisture and act as microbe-friendly niches.<\/p>\n The living ceramics could be used to make tiles for indoor use. \u201cWe are positioning ourselves against the glazed white tiles of laboratories \u2014 we look to challenge that,\u201d says Beckett.<\/p>\n A sample of concrete containing Bacillis subtilis. <\/span>Credit: Beckett Lab<\/span><\/p>\n For now, it is just a proof of concept. It\u2019s not clear whether a B. subtilis population would remain viable over the life of a building without maintenance, such as water or nourishment. It\u2019s also unclear whether the bacteria would be distributed throughout an indoor environment over time \u2014 and if that were to happen, whether this would be beneficial or harmful. The microbe is prevalent outdoors and is harmless to most people, but there are rare instances of B. subtilis infection in older people or those who are immunocompromised.<\/p>\n The transfer of microbes from the environment to people is extremely challenging to study \u2014 it\u2019s difficult to prove whether a person acquired a microbe from the environment or from another person, for instance.<\/p>\n One place it\u2019s easier to study is the tightly-controlled environment of the International Space Station. In 2021, researchers reported5 that an astronaut who was not carrying S. aureus in their nose before a mission nevertheless tested positive for the microbe three months later, while aboard the station.<\/p>\n Richard Beckett worked at a pharmaceutical company before becoming an architect.<\/span>Credit: Alecsandra Dragoi for Nature<\/span><\/p>\n Whether to prevent the spread of infectious diseases or to improve health by exposing people to beneficial microbes, it\u2019s important for researchers to understand what\u2019s present in the indoor environment. \u201cWhen we\u2019re using antimicrobials in cleaning products and in materials, we still find microbes,\u201d says Hartmann. \u201cIt\u2019s critical to think intentionally about what microbes are there.\u201d<\/p>\n Fretz is studying how materials influence the microbes found on indoor surfaces, and is paying especially close attention to wood.<\/p>\n Architects are increasingly interested in replacing concrete in construction with mass timber. This material, which is made by gluing blocks or sheets of wood together, is potentially more eco-friendly than concrete \u2014 the production of cement, a key ingredient, is responsible for around 8% of global carbon dioxide emissions. Wood is also renewable and can be sourced regionally.<\/p>\n But there is often reluctance from designers to use mass timber in places such as hospitals. One barrier is the perception that wood is not clean, Fretz says, so he\u2019s studying what really lives on the material.<\/p>\n Fretz was a dentist with the US Indian Health Service for a decade, and says that he switched from studying the microbes in people\u2019s mouths to those in buildings. He has shown that wood can in fact be very clean. Once timber is dried and brought indoors, microbes don\u2019t thrive on its surface \u2014 plaster, which is a common material in hospitals, hosts a higher abundance of viable microbes, he says.<\/p>\n Clay wall surfaces could host beneficial bacteria.<\/span>Credit: Beckett Lab<\/span><\/p>\n Wood can absorb water, so can help to maintain a steady, healthy level of humidity. But that changes when wood is coated \u2014 after varnishing, a wooden surface behaves more like plastic.<\/p>\n Tree species matter, too. As part of an exhibit at the art and architecture festival Venice Biennale 2023, Fretz\u2019s group gathered samples of wood from species around the world and sequenced the DNA of the microbes present. They then put the wood pieces on display, with the intention of sampling them again after they had been exposed to the festival crowd.<\/p>\n Mass timber samples are kept in controlled conditions that simulate hospital air and lighting.<\/span>Credit: Celeste Noche for Nature<\/span><\/p>\n The team is still working on the analysis. Wood emits different volatile compounds depending on the tree it comes from \u2014 which is why pine and cedar have such characteristic smells. Fretz thinks that this influences the surface microbiomes of the planks.<\/p>\n Another way to introduce microbes into indoor spaces is to bring in plants and their microbe-rich soils. There are some indications that this has health benefits for adults.<\/p>\n Mark Fretz uses a cleaning agent on the surface of mass timber.<\/span>Credit: Celeste Noche for Nature<\/span><\/p>\n A 2022 study6 showed that office workers who are exposed to green walls \u2014 large vertical structures covered with living plants, sometimes coupled with ventilation systems \u2014 had a greater diversity of benign microbes on their skin. This diversity was also associated with a decrease in the levels of some inflammation-driving proteins in the blood. There is also evidence7 that being in a room with plants can reduce some physiological indicators of stress.<\/p>\n A bespoke climate chamber at the Institute for Health in the Built Environment in Oregon can simulate various indoor conditions. <\/span>Credit: Celeste Noche for Nature<\/span><\/p>\n It is not yet certain, however, what it is about the plants that brings benefits, says Jeffrey Siegel, a buildings scientist who specializes in air quality at the University of Toronto in Canada.<\/p>\n Siegel is currently running a study to determine whether sharing a space with plants is still beneficial when people can\u2019t see them \u2014 something that would be expected if the effects were mediated by microbes or air quality, but not if a psychological effect is at play. \u201cMaybe adding microorganisms is not the thing, it\u2019s what people see,\u201d Siegel says. \u201cWe expect we won\u2019t see benefits if the plants are hidden.\u201d<\/p>\n Gwynne Mhuireach swabs wood species and finishes of flooring from Portland International Airport. <\/span>Credit: Celeste Noche for Nature<\/span><\/p>\n Researchers are also interested in how the soil of indoor plants might affect people. When people buy a bag of soil from the hardware store, its contents are usually something of a mystery to them. Often these commercial products contain fungi that can trigger allergies, as well as fungus gnats that can live in drains, says Cynthia Gibas, who studies microbial genomics at the University of North Carolina in Charlotte.<\/p>\n The Forest Valley at Jewel Changi Airport in Singapore is home to more than 60,000 plants.<\/span>Credit: Suhaimi Abdullah\/Getty<\/span><\/p>\n Because the indoor environment is a challenging one for plants to survive in, people might supplement the soil with plant probiotics \u2014 the make-up of which is also often unclear. Gibas and her team have purchased several of these products online and are currently testing what\u2019s in them, ahead of studies that will assess their effects on people.<\/p>\n Beckett is experimenting with a different way of bringing microbe-rich soil indoors that could require much less upkeep than a plant wall. He and his team have created a set of bioreceptive concrete tiles that are embedded with soil extract containing viable microbes.<\/p>\n The extract was supplied by Helsinki-based firm Uute Scientific, and combines commercial plant-based composts and plant material from the Finnish forest floor. A 2020 study8 showed that adding forest-floor materials to the outdoor spaces of Finnish daycare centres diversified the microbiota of children\u2019s skin, and that this was associated with changes in the levels of immune proteins in their blood.<\/p>\n Air-quality specialist Jeffrey Siegel.<\/span>Credit: Daria Perevezentsev\/U of T Engineering<\/span><\/p>\n Beckett anticipates that his concrete tiles will release similarly \u2018friendly\u2019 microbes that will have measurable effects on the people who share a space with them. As part of the project, he spent three weeks sitting near the tiles, while his collaborators periodically took samples of his blood. The samples are currently being analysed to test whether Beckett\u2019s immune system responded.<\/p>\n Probiotic architecture is not a universally popular prospect. \u201cJust because sterility is bad, it doesn\u2019t mean the opposite is good,\u201d says Siegel. Releasing microbes into a space \u201chas the potential for some enormous negative consequences\u201d, he says. Someone with a suppressed immune system owing to medication or a health condition would be particularly at risk of unintended effects. And this is not a small group of people. It is estimated9 that as many as 7% of the adult US population could be immunosuppressed. Among women, the prevalence might be nearer 8%.<\/p>\n Richard Beckett works on probiotic concrete wall panels containing soil material from forest floors in Finland.<\/span>Credit: Alecsandra Dragoi for Nature<\/span><\/p>\n Deliberately seeding hospitals and offices with microbes, perhaps without giving notice to the people inhabiting the spaces, might therefore be a risk. \u201cIf a diverse community of microorganisms is a good thing to give babies, don\u2019t try to give it indirectly through a building,\u201d says Siegel. \u201cWe\u2019ve been controlling the temperature of buildings for hundreds of years, and we still don\u2019t have that right.\u201d<\/p>\n Concrete and soil form probiotic panels.<\/span>Credit: Alecsandra Dragoi for Nature<\/span><\/p>\n Fretz still thinks it\u2019s worth exploring probiotic design now. \u201cThe unseen environment influences so much, but we don\u2019t design for it,\u201d he says. His goal is to create spaces that are microbially \u201crich and diverse, so that the commensal organisms we need can outcompete the pathogens\u201d. But the first moves in that direction could be as simple as enabling people to open their windows. In places with good outdoor air quality, ventilating buildings during summer nights could allow some outdoor microbes in while also reducing cooling costs.<\/p>\n Scientists are only just beginning to understand the microbiology of the built environment. Microbiologists know very little about what kinds of microbe to engineer exposures to, and have much to learn about the complex ecologies at play in the built environment. \u201cKitchen counters are not like agar,\u201d says Hartmann. Initial results are \u201ctantalizing\u201d, Gilbert says, but firm recommendations are still a way off. It\u2019s \u201cenough to justify careful probiotic-building experiments, but not yet a prescription\u201d, he says.<\/p>\n Mark Fretz at the Oregon campus of the Institute for Health in the Built Environment.<\/span>Credit: Celeste Noche for Nature<\/span><\/p>\n Hartmann says that researchers need better tools to understand which microbes are present in indoor environments, how they might influence our health, and what the mechanisms behind those influences are. Siegel agrees: \u201cWe need good science with placebos, starting small scale,\u201d he says. \u201cAnything else, and you\u2019re using people as guinea pigs.\u201d<\/p>\n As experiments continue, it is clear that the mood about microbes is changing. Whereas once they were seen as nothing but pests to remove from our homes and offices, now there is growing appreciation that a little microbial exposure might do some good. \u201cThere are myriad bacteria, fungi, archaea and viruses around us,\u201d says Hartmann. \u201cWe should accept and embrace them. We should approach this with a sense of wonder.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":" The natural world teems with microorganisms. Billions of species of bacteria, archaea, viruses and fungi make up complex ecosystems in the soil, water and air. The activity of these microbes sustains plants through their roots, animals through their guts and skin, and helps to regulate the planet\u2019s climate and chemical cycles. But people spend about<\/p>\n","protected":false},"author":1,"featured_media":27944,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[58],"tags":[10958,3852],"class_list":{"0":"post-27943","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-guests","9":"tag-microbes"},"_links":{"self":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/27943","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=27943"}],"version-history":[{"count":0,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/27943\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/media\/27944"}],"wp:attachment":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=27943"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=27943"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=27943"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Antibiotic architecture<\/h2>\n
Living materials<\/h2>\n
Embracing wood<\/h2>\n
Buildings in bloom<\/h2>\n
Prescription buildings<\/h2>\n