Our bodies are confused by this 21st-century world.
IN the last half-century, the prevalence of autoimmune disease — disorders in which the immune system attacks healthy tissue in the body — has increased sharply in the developed world. An estimated one in 13 Americans has one of these often debilitating, generally lifelong conditions. Many, like Type 1 diabetes and celiac disease, are linked with specific gene variants of the immune system, suggesting a strong genetic component. But their prevalence has increased much faster — in two or three generations — than it’s likely the human gene pool has changed.
Many researchers are interested in how the human microbiome — the community of microbes that live mostly in the gut and are thought to calibrate our immune systems — may have contributed to the rise of these disorders. Perhaps society-wide shifts in these microbial communities, driven by changes in what we eat and in the quantity and type of microbes we’re exposed to in our daily lives, have increased our vulnerability.
The maternal gut microbiome guides neo- and postnatal immune system development, a mouse study shows.
Pregnant mice expose their unborn pups to maternal gut microbes, which can affect the development of the innate immune system after birth, according to a study published today (March 17) in Science. The results challenge the notion that a pup’s own gut microbiome drives immune system development, suggesting that the molecular metabolites of the maternal microbiota are transferred to pups during gestation. This transfer of maternally derived microbial metabolites prepares the offspring’s immune system for exposure to the large variety of microbes that eventually populate the gut.
Oligosaccharides found in breast milk stimulate the activity of gut bacteria, promoting growth in two animal models of infant malnutrition.
Gut microbes isolated from human infants that showed stunted growth can boost growth in two animal models of malnutrition with the addition of certain breast milk–derived sugars to the animals’ diets, researchers reported. The study, published today (February 18) in Cell, identifies oligosaccharides in mammalian breast milk that appear critical for the maturation of the infant gut microbiome.
“This is an excellent study that highlights the importance of [mammalian] milk oligosaccharides for infant growth and development,” said Lars Bodeof the University of California, San Diego, who was not involved in the work.
The results could inform “work to develop tools and levers to nudge the gut microbiota into the right direction to get durable effects on infant health,” said study coauthor David Mills from the University of California, Davis.
Birth of a microbiome: Researchers smear babies with vaginal fluid
C-section newborns slathered with moms’ secretions may dodge lifelong health problems.
Birth, like life, is messy. But, while life’s messes often harm health, the untidiness of our entrance into the world may profoundly protect it—at least that’s a leading hypothesis among microbiome researchers.
Microbes picked up from mom while in or exiting the womb kick off humans’ lifelong association with the invisible critters that live in and on us and affect our health. In cases where that microbial colonization of a newborn goes awry, researchers have noted links to chronic health problems, such as asthma, obesity, allergies, and immune deficiencies. Researchers have also found that such a microbial debacle is often brought on by Cesarean delivery (C-section), which is a common surgical procedure to birth a baby through the mother’s abdomen rather than the normal shove down the birth canal.
To reverse the potential ill-fate of C-section babies, researchers smeared surgically delivered babies with the vaginal fluids from their mothers in the moments just after birth. After tracking the babies and their microbiomes for a month, the researchers report Monday in Nature Medicine that the quick slather partly restored normal microbiome development.
Modern disease theory must account for communities of commensal bacteria.
At the turn of the last century, German physician Heinrich Koch identified four critical criteria for determining whether or not a particular microbe causes a disease. The ideas behind them were crucial for advancing medicine and formalizing the germ theory of disease. Over the last century, these postulates have been updated as medicine has advanced.
In what may end up being the most recent of these updates, biologists Allyson Byrd and Julia Segre propose some adjustments to these classic medical postulates intended to bring them in line with analytic techniques based on DNA sequencing and the most current understanding of bacterial communities. Just as the previous updates to Koch’s postulates did, these proposed amendments incorporate cutting-edge scientific knowledge and add nuance to our understanding of the causes of disease.
Koch’s original postulates are that, if a microorganism causes a disease, then:
For every single case of the disease, the microorganism will be present.
Healthy people will not carry the microorganism—if they did, they would be sick.
The microorganism can be isolated and cultured in a lab, then used to infect new people.
The microorganism can be re-isolated from a person who was experimentally infected.
‘The freeze-dried poop method’ might not sound like a weight-loss strategy that would catch on, but—as some researchers are now testing—it may be an effective way to slim down.
In a randomized, controlled clinical trial starting this year, researchers will test out such a fecal formula for the treatment of obesity. They’ll also try to glean critical details about the human microbiome and its role in our health and metabolism. The trial, led by Elaine Yu, an assistant professor and clinical researchers at Massachusetts General Hospital, will involve taking fecal samples from lean, healthy donors then freeze-drying the stool, putting a gram or two into capsules, and giving them to 20 obese patients.
Such poop-packed pills, which are designed to replace a person’s intestinal microbes with those from a donor via their feces, have proven effective at treating tenacious gut infections. This has led researchers to ponder whether the transplants could remedy other health problems, including obesity and metabolic disorders. A few animal studies and some anecdotal data in humans suggests the answer is yes—and Yu hopes to get a final answer with the upcoming trial.
The immune system tolerates the colonization of commensal bacteria on the skin with the aid of regulatory T cells during the first few weeks of life, a mouse study shows.
he skin is home to millions of commensal bacteria and immune cells. Yet how the skin microbiome is established—in particular, why the immune system does not attack these bacteria—has been little studied. Now, a team led by researchers at the University of California, San Francisco (UCSF), has shown that, to establish tolerance by the immune system, colonization of the skin by commensal bacteria occurs during the first few days after birth in mice. The team’s findings were published today (November 17) in Immunity.
“This is an elegant and well-executed study showing a regulatory T cell–mediated establishment of commensal-specific tolerance,” said Keisuke “Chris” Nagao of the National Cancer Institute in Bethesda, Maryland, who was not involved in the work.
In a battle against an infection, antibiotics can bring victory over enemy germs. Yet that war-winning aid can come with significant collateral damage; microbial allies and innocents are killed off, too. Such casualties may be unavoidable in some cases, but a lot of people take antibiotics when they’re not necessary or appropriate. And the toll of antibiotics on a healthy microbiome can, in some places, be serious, a new study suggests.
In two randomized, placebo-controlled trials of healthy people, a single course of oral antibiotics altered the composition and diversity of the gut microbiome for months, and in some cases up to a year. Such shifts could clear the way for pathogens, including the deadly Clostridium difficile. Those community changes can also alter microbiome activities, including interacting with the immune system and helping with digestion. Overall, the data, published Tuesday in the journal mBio, suggests that antibiotics may have more side effects than previously thought—at least in the gut.
US scientists are asking the public to join them in their quest to mine the Earth’s soil for compounds that could be turned into vital new drugs.
Spurred on by the recent discovery of a potential new antibiotic in soil, the Rockefeller University team want to check dirt from every country in the world.
They have already begun analysing samples from beaches, forests and deserts across five continents.
But they need help getting samples.
Which is where we all come in.
On their Drugs From Dirt website, they say: “The world is a big place and we can’t get get to all of the various corners of it.
“We would like some assistance in sampling soil from around the world. If this sounds interesting to you – sign up.”
They want to hear from people from all countries and are particularly keen to receive samples from unique, unexplored environments such as caves, islands, and hot springs.
Such places, they say, could house the holy grail – compounds produced by soil bacteria that are entirely new to science.
Researcher Dr Sean Brady told the BBC: “We are not after hundreds of thousands of samples. What we really want is a couple of thousand from some really unique places that could contain some really interesting stuff. So it’s not really your garden soil we are after, although that will have plenty of bacteria in it too.”