Our bodies are composed of There are about 30 trillion human cells, but they host about 39 trillion microscopic cells. These communities of bacteria, viruses, protozoa, and fungi in our guts, mouths, skin, and elsewhere—collectively called the human microbiome—comprise more than just freeloaders and lurking pathogens. Instead, as scientists grow, these microbes create ecosystems that are essential to our health. A growing body of research aims to understand how disruptions in these delicate systems can rob us of the nutrients we need, disrupt digestion, and possibly cause pain in our bodies and minds.
But we still know so little about our microbiome that we’re only just beginning to answer the most fundamental question: Where do these microbes come from? Can it be spread from other people like a cold virus or a stomach bug?
Now the largest and most comprehensive analysis of the distribution of the human microbiome has provided some important clues. A study led by genomics experts at the University of Trento in Italy has found clues that microbiome organisms move widely between people, especially those who spend a lot of time together. The findings were published in January Naturefill important gaps in our understanding of how people assemble and modify their microbiomes throughout life.
Other scientists have praised the research. Jose Clemente Litra, an associate professor of genetics and genomic sciences at the Icahn School of Medicine at Mount Sinai, hailed the work as “remarkable” and said it was the first clear measure of how much sharing is expected between family members or cohabitants. together.
In addition, the research has fueled the intriguing speculation that microbes can increase or decrease the risk of developing diseases such as diabetes or cancer—and thus bring an infectious dimension to diseases that are often not known to be infectious. Brett Finlay, a professor of microbiology at the University of British Columbia, wrote the opinion Science In the year About that possibility in 2020, the findings “put the final nail in the coffin that noncommunicable diseases probably shouldn’t be called that.”
An unknown difference
Microbiomes are like fingerprints: they are so diverse that no two people have the same. They’re also incredibly dynamic—they grow, shrink, and evolve over a person’s lifetime, so a baby’s microbiome looks very different as it grows. A few microbial species are found in more than 90 percent of people in Western societies, but most species are found in 20 percent to 90 percent of people. (Even Escherichia coli(Perhaps the only gut bacteria that most people can name is 90 percent less frequent.) Studies show that non-Western societies have more diverse microbes and more dynamic microbiomes.
In a population, any two randomly selected individuals have less than half of their microbiome species in common—on average, the microbial overlap in the gut is between 30 percent and 35 percent. Microbiologists argue that there is a “core” set of microbes that all healthy people have, but if there is, it’s probably a single-digit percentage of the total.
Determining how often microbes are transmitted between people, however, is a more difficult problem than looking for species. A single species may contain many different species or genetic variants. Therefore, researchers should be able to identify individual species by looking at genes in microbiome samples. There may be 2 to 20 million unique microbial genes in the human microbiome. Microbes are constantly changing their genes, changing and growing.