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Milwaukee is home to some of the most diverse ecosystems on Earth, with major effects on our health, environment, and our daily lives, hiding just outside of our sight. Here, we put our city under the microscope, to look at our tiniest residents, and how their lifestyles shape our own.

E. coli – one of the most famous bacteria living within humans. Credit: National Institute of Allergy and Infectious Diseases, National Institutes of Health

Milwaukee is home to an incredibly diverse community of over 600,000 humans in the city, and over 1.5 million humans in it’s metro region. Within every single human in our region, and on every exposed surface, are trillions of tiny residents, for every single human. These microscopic residents of us: bacteria, viruses, and others, form complex ecosystems that rival the forests in the Kettle Moraine, or those of Lake Michigan.

Science has long known that bacteria and other microscopic life (microbes) form complex communities. These communities, called microbiomes, exist in nearly every environment on earth, each one tailoring itself to its  environment, trying to survive and thrive. Bacteria are fiercely competitive. Some will produce antibiotics to take out the competition, while others, ones in the human body, will work with their host in order to make their own lives easier. These interactions benefit both us humans, and our bacteria: we get vitamins, help absorbing nutrients, and protection from diseases from our bacteria, all in return for us feeding our microbiome.

From more recent experiments looking at the makeup of the bacteria that live within us, we now know that our tiny friends play major roles in our health. In mice, we have seen that these microbes that live in obese mice can make other mice gain weight. We have seen that some types of microbes in anxious mice can cause other mice to develop anxiety. We have seen that damaging the ecosystems within us can increase our risks for developing damaging, if not dangerous, diseases, including some of the more common hospital-acquired infections. We even have been able to treat these diseases by taking bacteria from a healthy person and putting them into a sick one. The microbiome plays such a major role in our health that we work to encourage a healthy one from birth. Breastmilk contains everything a growing baby needs, plus nutrients that a young human cannot use. These nutrients appear to be designed for friendly bacteria to eat, helping to set up the microbiome. The importance of creating and maintaining a good relationship with our bacteria and the major impacts these bacteria play in our lives becomes more and more monumental with each new study.

Here in Milwaukee, we have some of our own scientists and their research teams actively studying microbiomes in order to make our lives better. Dr. Sandra McLellan at the University of Wisconsin, Milwaukee looks at how the microbiomes of lakes can work to stop disease-causing bacteria from taking root, as well as what these communities can teach us about the impacts of pollution on our lakes. Dr. Nita Salzman at the Medical College of Wisconsin works to understand exactly what changes happen to bacteria when they take up residence in our bodies, as well as how certain genetic defects can harm our microbes. Dr. Silvia Munoz-Price, also at the Medical College of Wisconsin, works to see what changes happen to microbes in the gut before certain infections happen, and how this could be used to prevent patients from becoming sick.

Right now, the big questions we face in our understanding of our microbial neighbors include how to untangle some of the complex interactions between different bacteria in order to see what roles they play in both health and disease, how our microbiomes can be changed, and how our microbiomes can heal after injury. Our microbiomes could even function as powerful indicators of our health and our environment, able to serve as an early warning system. Our understanding of the microbiome is still fairly new, with plenty of exciting discoveries on the horizon. As we gain new insights into our smallest neighbors, it is becoming clear that keeping them happy and healthy will be key in both our own health, and the health of our region.

Further Reading

I Contain Multitudes  – Ed Yong

The Gut’s Microbiome Changes Rapidly with Diet – Rachel Feltman, Scientific American

Some of My Best Friends are Germs – Michael Pollan, New York Times Magazine

Mental Health May Depend on Creatures in the Gut – Charles Schmidt, Scientific American

Breastfeeding the Microbiome – Ed Yong, New Yorker


Written by John Uhrig for the Milwaukee Area Science Advocates

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