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Since humans first understood the concept of germs, we’ve worked tirelessly to eliminate or reduce them in our surroundings and bodies. The market for antimicrobial products is already thriving and is expected to be worth $4.19 billion by 2021. The largest demand comes from the healthcare sector, closely followed by the indoor air and HVAC industries, which serve both private and public spaces.
Despite our efforts, the average household is home to thousands of different microbial species, which can reveal fascinating details about the people living there. Researchers from the University of Colorado at Boulder collected dust samples from 1,200 homes across the U.S. and sequenced the DNA to build a database of bacteria and fungi. The samples were paired with questionnaires, helping the researchers confirm their findings. The results were an invaluable source of information, potentially leading to new advancements in microbial research and even forensic science.
10. You’ve Been to Space
Under a microscope, it’s easy to spot if you’ve recently returned from the International Space Station (ISS). The J. Craig Venter Institute has been examining the ISS, focusing specifically on its tiniest residents: microbes. The environment within the ISS is as close to sterile as possible. The air is filtered, surfaces are designed to prevent bacterial growth, and the water undergoes filtration with iodine and biocidal nano-silver capsules. The astronauts themselves are the only source of microbes.
Hernan Lorenzi’s team is investigating the microbiomes of astronauts on behalf of the institute. Their research has revealed weakened immunity linked to lower diversity in the astronauts' microflora. When this diversity is reduced, the immune system essentially goes into hibernation, pausing its functions until new microbes—whether harmful or harmless—enter the body. Scientists are concerned about the potential impact of this on astronauts upon their return to Earth, and how it may affect them on missions to distant planets like Mars.
9. City Life vs. Country Life
Much like astronauts in a controlled environment, city dwellers have less microbiome diversity compared to those living in rural areas. A 2018 study compared the microbiomes of urban and rural populations from the same region in Nigeria. Previous research compared the gut flora of Americans to that of hunter-gatherer tribes, but these comparisons were hindered by vast geographic differences. This new study showed that people living in cities with a “western-style diet” have significantly less diverse gut microbiomes.
The rural population, in contrast, had more microbiome diversity, and this diversity began at a much earlier age. Children in cities generally reached peak diversity by age three, while rural children achieved this much earlier, just a few months after birth. Research has shown that microbiome diversity correlates with better overall health. Several factors may contribute to this difference, including the rural community's lower consumption of processed foods and filtered water, as well as the higher rates of breastfeeding among infants. Additionally, antibiotics—which can destroy beneficial gut bacteria—were used far less frequently in the rural area.
8. Where You Live
The health of our bodies may depend on bacteria, but when it comes to tracking objects, it's the microscopic fungi that coexist with us in our homes that hold the key. The best way to identify what fungi might be in a building is by its location. These fungi arrive through open windows or doors, or they hitch a ride on our clothes, setting up colonies wherever decaying matter is present. Dark, dusty corners in our homes are ideal spots for fungi to settle in.
A 2011 study conducted by Rob Dunn and Noah Fierer at the University of Colorado discovered that homes in the eastern U.S. have distinctly different fungi compared to those in the western part of the country. Additional studies over the following four years showed that fungi are even more accurate in pinpointing locations. By analyzing fungal DNA, dust samples can be traced back to within a 240-kilometer (150-mile) radius. With further investigation, the team hopes to advance forensic mycology using this technique.
7. Where You’ve Been
In the realm of forensic science, microbes left on objects can reveal more than just fingerprints or DNA. A unique database of microbial profiles could be used to compare swabs and identify who has touched something, much like how DNA analysis works today. The critical difference, however, is that microbes deteriorate over time, meaning the traces left behind can not only reveal who was present but also when.
Even without the need for a database to cross-reference individuals, leftover microbes can provide clues about the person they originated from. For instance, the microbes found on office workers' skin will differ significantly from those on a farmer's. A detailed analysis of these microbial traces can offer insights into one's occupation, living situation, geographic location, and even gender. Each microbial profile is highly individual, and scientists are striving to decode the vast array of personal information microbes can reveal.
6. You Don’t Get Out Much
The microbes residing on our skin may one day help scientists track our movements, but those within our bodies can already indicate places we haven't been. A growing number of people are spending increasingly less time outdoors, and this shift is clearly visible in their gut microbiomes. Remaining indoors is akin to life on a space station in this regard, where air is constantly recycled, and the microbial environment is almost entirely self-generated. While some foreign microbes still enter through activities like going out or consuming food, it's challenging to maintain a diverse gut flora without spending time in nature.
The hygiene hypothesis posits that societal changes have led to a decrease in children's exposure to the bacteria that are essential for developing their immune systems. Early exposure to these bacteria has been shown to reduce the risk of allergies and other health issues. Interestingly, even adults seem capable of improving their gut health by reconnecting with the outdoors. Engaging in activities such as gardening can help to diversify one's microbial environment.
Although scientists don’t openly recommend that patients consume dirt, one experiment has demonstrated that soil-based microbes can have antidepressant effects when injected. In 2004, oncologist Mary O’Brien, working at the Royal Marsden Hospital in London, conducted a study where cancer patients were injected with Mycobacterium vaccae, a harmless soil bacteria. While it didn’t provide the immune boost she had hoped for, the results were still promising. Patients reported feeling happier, more energetic, and showed improvements in cognitive function.
5. You Have Pets
If you're looking to diversify your gut microbiome and invite a range of exciting new microbes into your home, adopting a dog could be the way to go. The influence of man's best friend is so powerful that researchers can identify whether a person owns a dog based solely on their microbial composition, with an accuracy rate of 99 percent. Even the dust in a home can reveal the presence of a dog, with a 92 percent accuracy rate. Cats, though, do impact the home environment too, but their effect is less pronounced, likely due to their limited outdoor activity compared to dogs.
For many, owning dogs may seem like a challenge in terms of cleanliness. However, children from urban families with dogs have been found to have fewer allergies and asthma. In contrast, those with cats, who generally stay indoors, and those from rural areas, where people venture outside frequently, show less improvement. Researchers believe the key factor is the small amounts of dirt that dogs bring indoors. Another possibility is that microbes are exchanged between humans and dogs through activities like dog kisses and paw-handshakes. Some children even host dog-specific gut microbes that permanently settle in their digestive systems.
4. What You Eat
It was once believed that the bacteria in our gut originated from our mouths, but recent studies are challenging this idea. The fascinating part is that it’s less about the specific diets we often categorize ourselves into and more about the variety and processing of the food we consume. In 2014, researchers examined the microbes associated with three distinct diets. The first, dubbed the 'American diet,' consisted of fast food and convenience meals. The second, the USDA-recommended diet, featured a balance of lean proteins, fruits, vegetables, dairy, and whole grains. The third diet, a vegan approach, excluded all animal products.
Despite the other nutrients, scientists at the University of California analyzed the microbial content in different diets. The USDA-recommended diet dominated the others, with an impressive 1.3 billion microbes consumed daily. The vegan diet came in second with only 6 million microbes, and the American diet ranked last with a mere 1.4 million. However, these diets are far more specifically structured than the average person's eating habits. Rob Knight, a researcher with the American Gut Project, points out that a vegan who primarily eats fries won’t experience the same microbial diversity as one who primarily consumes kale. Under a microscope, the microbes will reveal which vegan follows which eating pattern.
3. You Clean Too Much
Many people are disgusted by the idea of microbes living on every surface, hiding in dusty crevices, and making their way onto our bodies. The typical response is to grab some bleach wipes and scrub everything down. However, as we've learned from our friends in rural areas, this approach may not be as beneficial as we once thought. Not only does an overly sterile environment hinder the immune system, but it can also contribute to the rise of antimicrobial-resistant infections. These so-called superbugs have researchers around the globe scrambling for new solutions to diseases that were once easy to treat.
The jokes about the minuscule percentage left behind by antimicrobial soaps might hold some truth. When most of a microbiome is eradicated, what's left tends to be harmful. Mary Ruebush, a microbiologist and instructor at Becker Professional Education School, warns that this is especially true for our skin. Keeping pathogens at bay is often a battle between harmful bacteria and the beneficial microbes that inhabit our bodies. Excessive washing can disrupt the protective barrier that keeps us safe from dangerous bacteria and fungi. Ruebush is quick to emphasize that washing is necessary, but it’s important to focus on the areas that smell and give the rest of the body a break every now and then.
2. Who You Touch
The dynamics of gender aren't typically the most scandalous secrets in a home, but intimate moments are often kept hidden. We're lucky that our microbes don’t spill the beans. Roommates exchange more microbes than friends who don’t share a living space, but couples reach a whole new level of microbial connection. A brief, ten-second kiss can transfer a staggering 80 million bacteria. If a couple kisses up to nine times a day, their oral bacterial makeup can change significantly. That’s all it takes.
The microbes on your skin are influenced by who you share your bed with. Studies have shown that couples swap the most microbes on areas like the feet, torso, navel, and eyelids. These parts of the body tend to collect bacteria after sharing a bed for hours. Surprisingly, the thighs don't exchange as many microbes, but it’s well-known that sexual activities often lead to the transfer of many microbes and viruses internally. Although these are typically grouped with STIs, one STI, GB virus C (GBV-C), has proven beneficial. It reduces the severity of HIV and boosts survival rates for individuals infected with both. Scientists have even speculated that beneficial STIs may have played a role in the development of promiscuity in humans. So, if microbes ever expose our infidelities, they might just offer us a plausible excuse.
1. Who You Live With
The long-standing battle of the sexes in the bathroom has often revolved around picking up towels or putting the toilet seat down, but it turns out there’s also a microbial battle. The University of Colorado has uncovered a fascinating difference in the dust found in our homes, and it’s all about bacteria. The key difference is the presence of Lactobacillus, a dominant bacteria in the vaginal microbiome. In households where women outnumber men, Lactobacillus flourishes. This probiotic bacterium helps suppress harmful bacteria, and it’s also found in foods like yogurt and beer, which explains why homes with more women may have a slight sour smell.
In contrast, homes with an equal gender distribution or a higher male population are home to hearty colonies of Corynebacterium, Dermabacter, and Roseburia. The first two thrive on skin, while the latter lives in the human gut. Corynebacterium, in particular, resides in the armpits, creating body odor. Rob Dunn, a researcher, humorously admits that homes with more men might have a distinct 'armpit' smell. However, men aren't the only ones carrying smelly bacteria. Women also carry these skin and fecal bacteria, just in smaller amounts. Moreover, women are typically smaller than men and shed less skin, possibly due to differences in hygiene practices or moisturizing habits.
