Nav: Home

Microbiome diversity is influenced by chance encounters

March 03, 2017

CAMBRIDGE, MA Within the human digestive tract, there are trillions of bacteria, and these communities contain hundreds or even thousands of species. The makeup of those populations can vary greatly from one person to another, depending on factors such as diet, environmental exposure, and health history.

A new study of the microbe populations of worms offers another factor that may contribute to this variation: chance.

MIT researchers found that when they put genetically identical worms into identical environments and fed them the same diet, the worms developed very different populations of bacteria in their gut, depending on which bacteria happened to make it there first.

"This study shows that you can have heterogeneity that's driven by the randomness of the initial colonization event. That's not to say the heterogeneity between any two individuals has to be driven by that, but it's a potential source that is often neglected when thinking about this variation," says Jeff Gore, the Latham Family Career Development Associate Professor of Physics at MIT.

Gore is the senior author of the study, which appears in the March 3 issue of the journal PLOS Biology. The paper's lead author is MIT postdoc Nicole Vega.

A simple model

Variations in the human gut microbiome have been shown to contribute to gastrointestinal disorders such as colitis and Crohn's disease, and studies suggest that microbiome composition can also influence diabetes, heart disease, and cancer.

"We know that gut communities are different within different individuals, and that this could have really important implications for health and disease, but it's often difficult to figure out the origin of this diversity between different individuals," Gore says.

The researchers chose to study the worm C. elegans because it is among the simplest animals with a digestive tract colonized by bacteria, offering a way to model what might be happening in the human gut.

"What you would like to do is take a bunch of identical individuals, place them in identical environments, and then look to see whether the microbial communities are the same or different. That's a very difficult experiment to do with people, but with model organisms it's feasible," Gore says.

C. elegans consume bacteria as part of their normal diet, so the researchers first fed a group of genetically identical worms a mix of six different species of bacteria. When the experiment began, the worms had no bacteria in their digestive tracts, but after being exposed to the identical bacterial diet, the worms each generated very different microbe populations in their guts.

The researchers explored this further by feeding the worms a mix of only two types of bacteria, making it easier to study their interactions. In this scenario, all of the bacteria were E. coli, but half were engineered to produce a green fluorescent protein and the other half produced a red fluorescent protein.

After a week of this diet, each worm had about 30,000 bacteria in its digestive tract. However, these populations were not evenly divided between red and green. Instead, each population was dominated by one or the other. This happens, Gore says, because the initial colonization of the gut is a rare event, so whichever microbe makes it there first tends to dominate the entire population.

"Whichever color bacteria is lucky and happens to survive getting eaten and sticks to the gut, this bacterium starts growing, and it can grow to dominate the gut community," he says.

This randomness tends to prevail when the colonization rate is low. When the researchers fed the worms larger amounts of bacteria, the colonization rate went up and the researchers found much less variation among individuals' microbe populations.

An overlooked source

The researchers also found the same effect when they fed the worms two different species of bacteria: Enterobacter aerogenes and Serratia marcescens.

Gore says that this random variability may contribute to the differences in microbe populations seen in the human gut as well, since usually only a small fraction of bacteria consumed by humans and other animals survives the digestion process. However, many other factors such as environmental exposure also play roles, he says.

"I don't believe that stochastic colonization is the only or dominant source of heterogeneity between individuals, but I think it's a source of heterogeneity that is often overlooked," Gore says.

His lab is now studying many different pairs of bacterial species in the worm gut to see if the outcome of competition between two species can be used to predict the outcome when three or more species are competing.
-end-
The research was funded by the National Institutes of Health, the National Science Foundation, a Pew Fellowship, and a Sloan Foundation Fellowship.

Massachusetts Institute of Technology

Related Bacteria Articles:

Bacteria might help other bacteria to tolerate antibiotics better
A new paper by the Dynamical Systems Biology lab at UPF shows that the response by bacteria to antibiotics may depend on other species of bacteria they live with, in such a way that some bacteria may make others more tolerant to antibiotics.
Two-faced bacteria
The gut microbiome, which is a collection of numerous beneficial bacteria species, is key to our overall well-being and good health.
Microcensus in bacteria
Bacillus subtilis can determine proportions of different groups within a mixed population.
Right beneath the skin we all have the same bacteria
In the dermis skin layer, the same bacteria are found across age and gender.
Bacteria must be 'stressed out' to divide
Bacterial cell division is controlled by both enzymatic activity and mechanical forces, which work together to control its timing and location, a new study from EPFL finds.
How bees live with bacteria
More than 90 percent of all bee species are not organized in colonies, but fight their way through life alone.
The bacteria building your baby
Australian researchers have laid to rest a longstanding controversy: is the womb sterile?
Hopping bacteria
Scientists have long known that key models of bacterial movement in real-world conditions are flawed.
Bacteria uses viral weapon against other bacteria
Bacterial cells use both a virus -- traditionally thought to be an enemy -- and a prehistoric viral protein to kill other bacteria that competes with it for food according to an international team of researchers who believe this has potential implications for future infectious disease treatment.
Drug diversity in bacteria
Bacteria produce a cocktail of various bioactive natural products in order to survive in hostile environments with competing (micro)organisms.
More Bacteria News and Bacteria Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.