Genes Help Determine a Person's Microbial Mix: In Mice and Humans, Genetic Variants Seem to Control Which Bacteria Live on and in Bodies
Saey, Tina Hesman, Mole, Beth, Science News
BOSTON -- Humans may be in charge of which bacteria live in and on them, researchers report. Scientists used to think that what people ate and where they lived were the main determinants of the microbes that colonize human bodies, but new studies suggest that the immune system plays a big role in selecting its microbial companions.
The selection process may make it harder to change which microbes call a person's body home.
Studies of mice and humans presented at the annual meeting of the American Society of Human Genetics suggest that a host's genetic makeup may determine which microbes set up shop in the intestines, on the skin and in other parts of the body. And a paper appearing October 29 in Genome Research finds that people with immune disorders host a wider variety of bacteria and fungi, some harmful, on their skin than do healthy people.
The set of microbes living in and on a host organism--known as the microbiome--is highly individual, said Andrew Benson of the University of Nebraska-Lincoln. Even mice that live in the same laboratory conditions may have widely varying microbiomes.
To find out why animals develop a certain microbiome, Benson and colleagues studied microbes of genetically diverse mice. When the researchers characterized which bacteria lived in the mice's intestines, they saw "a shotgun blast of diversity," Benson reported October 23.
Which microbes are present may not be as important as what they do for the host, so Benson's team determined the services the bacteria provide. The team found that mice with some genetic variants tend to harbor bacteria that make molecules important for communication between immune cells.
Mice with variants in proteins that bind to certain amino acids tended to have more bacteria that produce those same amino acids, the team found. Variants in some of the mice's immune system genes were also associated with particular microbial mixes. The mice's own genes seem to encourage the growth of some microbes while discouraging others, Benson said.
"It's beautiful work," said Ran Blekhman of the University of Minnesota, Twin Cities. Blekhman has come to similar conclusions using data gleaned from the human microbiome project, an effort to catalog people's microbes (SN: 6/16/12, p. 15).
The more similar two people's genetic makeups are, the more similar their microbiomes, Blekhman reported October 24. In particular, human genes involved in regulating the immune system are associated with the types of microbes that reside in a person. …