The microbiome comprises trillions of microorganisms living on and inside each of us. Historically, some researchers have guessed at its role in human health, but in the last decade or so genetic sequencing techniques have illuminated this galaxy of microorganisms enough to study it in detail.
As researchers unravel the complex interplay between our bodies and microbiomes, they are beginning to appreciate the full scope of the field's potential for treating disease and promoting health.
For instance, the growing list of conditions that correspond with changes in the microbes of our gut includes type 2 diabetes, inflammatory bowel disease, Alzheimer's disease, and a variety of cancers.
"In almost every disease context that's been investigated, we've found different types of microbial communities, divergent between healthy and sick patients," says professor of biological engineering Eric Alm. "The promise [of these findings] is that some of those differences are going to be causal, and intervening to change the microbiome is going to help treat some of these diseases."
Alm's lab, in conjunction with collaborators at the Broad Institute of MIT and Harvard, did some of the early work characterizing the gut microbiome and showing its relationship to human health. Since then, microbiome research has exploded, pulling in researchers from far-flung fields and setting new discoveries in motion. Startups are now working to develop microbiome-based therapies, and nonprofit organizations have also sprouted up to ensure these basic scientific advances turn into treatments that benefit the maximum number of people.
"The first chapter in this field, and our history, has been validating this modality," says Mark Smith PhD '14, a co-founder of OpenBiome, which processes stool donations for hospitals to conduct stool transplants for patients battling gut infection. Smith is also currently CEO of the startup Finch Therapeutics, which is developing microbiome-based treatments. "Until now, it's been about the promise of the microbiome. Now I feel like we've delivered on the first promise. The next step is figuring out how big this gets."
An interdisciplinary foundation
MIT's prominent role in microbiome research came, in part, through its leadership in a field that may at first seem unrelated. For decades, MIT has made important contributions to microbial ecology, led by work in the Parsons Laboratory in the Department of Civil and Environmental Engineering and by scientists including Institute Professor Penny Chisholm.
Ecologists who use complex statistical techniques to study the relationships between organisms in different ecosystems are well-equipped to study the behavior of different bacterial strains in the microbiome.
Not that ecologists - or anyone else - initially had much to study involving the human microbiome, which was essentially a black box to researchers well into the 2000s. But the Human Genome Project led to faster, cheaper ways to sequence genes at scale, and a group of researchers including Alm and visiting professor Martin Polz began using those techniques to decode the genomes of environmental bacteria around 2008.
Those techniques were first pointed at the bacteria in the gut microbiome as part of the Human Microbiome Project, which began in 2007 and involved research groups from MIT and the Broad Institute.
Alm first got pulled into microbiome research by the late biological engineering professor David Schauer as part of a research project with Boston Children's Hospital. It didn't take much to get up to speed: Alm says the number of papers explicitly referencing the microbiome at the time could be read in an afternoon.
The collaboration, which included Ramnik Xavier, a core institute member of the Broad Institute, led to the first large-scale genome sequencing of the gut microbiome to diagnose inflammatory bowel disease. The research was funded, in part, by the Neil and Anna Rasmussen Family Foundation.
The study offered a glimpse into the microbiome's diagnostic potential. It also underscored the need to bring together researchers from diverse fields to dig deeper.
Taking an interdisciplinary approach is important because, after next-generation sequencing techniques are applied to the microbiome, a large amount of computational biology and statistical methods are still needed to interpret the resulting data - the microbiome, after all, contains more genes than the human genome. One catalyst for early microbiome collaboration was the Microbiology Graduate PhD Program, which recruited microbiology students to MIT and introduced them to research groups across the Institute.
As microbiology collaborations increased among researchers from different department and labs, Neil Rasmussen, a longtime member of the MIT Corporation and a member of the visiting committees for a number of departments, realized there was still one more component needed to turn microbiome research into a force for human health.
"Neil had the idea to find all the clinical researchers in the [Boston] area studying diseases associated with the microbiome and pair them up with people like [biological engineers, mathematicians, and ecologists] at MIT who might not know anything about inflammatory bowel disease or microbiomes but had the expertise necessary to solve big problems in the field," Alm says.
In 2014, that insight led the Rasmussen Foundation to support the creation of the Center for Microbiome Informatics and Therapeutics (CMIT), one of the first university-based microbiome research centers in the country.
Tami Lieberman, the Hermann L. F. von Helmholtz Career Development Professor at MIT, whose background is in ecology, says CMIT was a big reason she joined MIT's faculty in 2018. Lieberman has developed new genomic approaches to study how bacteria mutate in healthy and sick individuals, with a particular focus on the skin microbiome.
Laura Kiessling, a chemist who has been recognized for contributions to our understanding of cell surface interactions, was also quick to joint CMIT. Kiessling, the Novartis Professor of Chemistry, has made discoveries relating to microbial mechanisms that influence immune function. Both Lieberman and Kiessling are also members of the Broad Institute.
Today, CMIT, co-directed by Alm and Xavier, facilitates collaborations between researchers and clinicians from hospitals around the country in addition to supporting research groups in the area. That work has led to hundreds of ongoing clinical trials that promise to further elucidate the microbiome's connection to a broad range of diseases.
Fulfilling the promise of the microbiome
Researchers don't yet know what specific strains of bacteria can improve the health of people with microbiome-associated diseases. But they do know that fecal matter transplants, which carry the full spectrum of gut bacteria from a healthy donor, can help patients suffering from certain diseases.
The nonprofit organization OpenBiome, founded by a group from MIT including Smith and Alm, launched in 2012 to help expand access to fecal matter transplants by screening donors for stool collection then processing, storing, and shipping samples to hospitals. Today OpenBiome works with more than 1,000 hospitals, and its success in the early days of the field shows that basic microbiome research, when paired with clinical trials like those happening at CMIT, can quickly lead to new treatments.
"You start with a disease, and if there's a microbiome association, you can start a small trial to see if fecal transplants can help patients right away," Alm explains. "If that becomes an effective treatment, while you're rolling it out you can be doing the genomics to figure out how to make it better. So you can translate therapeutics into patients more quickly than when you're developing small-molecule drugs."
Another nonprofit project launched out of MIT, the Global Microbiome Conservancy, is collecting stool samples from people living nonindustrialized lifestyles around the world, whose guts have much different bacterial makeups and thus hold potential for advancing our understanding of host-microbiome interactions.
A number of private companies founded by MIT alumni are also trying to harness individual microbes to create new treatments, including, among others, Finch Therapeutics founded by Mark Smith; Concerto Biosciences, co-founded by Jared Kehe PhD '20 and Bernardo Cervantes PhD '20; BiomX, founded by Associate Professor Tim Lu; and Synlogic, founded by Lu and Jim Collins, the Termeer Professor of Medical Engineering and Science at MIT.
"There's an opportunity to more precisely change a microbiome," explains CMIT's Lieberman. "But there's a lot of basic science to do to figure out how to tweak the microbiome in a targeted way. Once we figure out how to do that, the therapeutic potential of the microbiome is quite limitless."
