CREDITS: (GRAPHIC C. BICKEL/
SCIENCE
; (DATA U.S. NATIONAL LIBRARY OF MEDICINE/NATIONAL CENTER FOR BIOTECHNOLOGY INFORMATION; U.N. DEPARTMENT OF ECONOMIC AND
SOCIAL AFFAIRS/POPULATION DIVISION (2019 ,WORLD POPULATION PROSPECTS 2019, ONLINE EDITION. REV. 1; R.J. ABDILL, E.M. ADAMOWICZ; R. BLEKHMAN/UNIVERSITY OF MINNESOTASCIENCE science.org 18 FEBRUARY 2022 • VOL 375 ISSUE 6582 709T
housands of studies have linked the
trillions of microbes living in and on
our bodies to conditions from cancer to
autism to depression. But most micro-
biome samples come from wealthy
countries in North America and Eu-
rope, a new analysis finds, distorting our un-
derstanding of human-microbe interactions.
“There are many ethnic groups and
geographical locations that are dramati-
cally underrepresented,” says Rob Knight, a
microbiologist at the University of California,
San Diego, who was not part of the study.
The distribution of samples “speaks to deep
inequities in how research
is funded and conducted.” A
fuller picture of how different
microbiomes impact health
could aid the development
of diagnostics and therapies
for specific populations, says
Knight, who is working to
make microbiome sampling
more equitable.
Unlike the human ge-
nome, which only varies
slightly among individuals,
the human microbiome dif-
fers radically. Diet, exercise,
socioeconomic status, antibi-
otic use, and even pollution
can influence its makeup,
with some studies suggesting
geography is one of the stron-
gest variables.
Research comparing the
gut microbiomes of people from the Amazo-
nas state in rural Venezuela, rural Malawi, and
U.S. metropolitan areas shows microbiomes
in less industrialized environments are more
diverse. Studies have also found that com-
pared with microbiomes in urban popula-
tions, those of hunter-gatherers in Tanzania
are very dynamic, changing with the seasonal
availability of foods.
To see how well microbiome research cap-
tures these global variations, Ran Blekhman,
Elizabeth Adamowicz, and Richard Abdill
of the University of Minnesota, Twin Cities,
compiled geographic information for more
than 440,000 publicly available microbial
DNA sequences from the past 11 years. They
found more than 40% of the samples were
from the United States—almost five times asmany as from any other country, the scien-
tists report this week in PLOS Biology.
The researchers then compared the
number of samples with each region’s
population. They found Europe and North
America provided more than 71% of sam-
ples even though they hold about 15% of
the world’s population, whereas central and
southern Asia contributed 1.5% of samples
from almost 26% of the world’s population.
“It is clear that our understanding of the
‘human’ microbiome does not include most
humans,” Abdill says. “Our study is a step
towards quantifying this disparity.”
Clement Adebamowo, an epidemiologist
at the University of Maryland, Baltimore,agrees. “[The authors] have done a great ser-
vice to the field by highlighting the scope of
the problem,” he says.
The sparse representation of developing
countries reflects low levels of research fund-
ing, lack of state-of-the-art technology, and
few people trained to analyze samples, says
Adebamowo, who has a joint appointment
at the Institute of Human Virology, Nigeria.
Countries may also focus research efforts on
more urgent needs, such as malaria, he says.
The cost of equipment to identify bacteria
is a major barrier. “[We] have a very difficult
time having access to those technologies,”
says Pablo Jarrín Valladares, a biologist at the
National Institute of Biodiversity in Quito, Ec-
uador, who leads the Ecuadorian Microbiome
Project. Bureaucracy can also delay the per-mits required for sampling. “The issue for us
in catching up is reducing the bumps.”
A lack of specialists to analyze data is an-
other obstacle in developing countries, says
Victor Pylro, a molecular microbial ecologist
at the Federal University of Lavras and coor-
dinator of the Brazilian Microbiome Project.
He, Jarrín Valladares, and other researchers
hope to attract funding from the private sec-
tor and foreign institutions by forming local
networks. With funding from Thermo Fisher
Scientific, Pylro’s team is already working to
evaluate how the microbiome changes when
people have COVID-19.
Blekhman, Knight, and others point
to the Human Heredity and Health in
Africa (H3Africa) consor-
tium, which has boosted ge-
nomic science in the region,
as an example of local groups
improving sampling and data
sharing. Adebamowo, who
leads H3Africa’s African Col-
laborative Center for Micro-
biome and Genomics Re-
s e a r c h ( A C C M E ) , s a y s t h e c o n -
sortium has helped African
researchers build infrastruc-
ture and expertise, and is now
taking on microbial diversity
in health and disease. At
ACCME, Adebamowo and
colleagues are working to
find biomarkers linking vari-
ations in the vaginal microbi-
ome with persistent high-risk
human papillomavirus infec-
tions in African women.
For María Gloria Domínguez Bello, a
microbiome researcher at Rutgers Univer-
sity, New Brunswick, having samples from
populations across the world is essential
to understanding not just disease, but also
human history and diversity. “Our micro-
biomes are coevolved entities,” she says.
“These are genomes that belong to us in the
sense that we can’t live without them, and
they can’t live without us.” She, Knight, and
others have launched a Microbiota Vault in
Basel, Switzerland, a storage project akin to
the “doomsday” crop seed vault, aiming to
preserve microbiome samples from all over
the world.
“With the way the field is growing, the best
time to course correct was 5 years ago,” Abdill
says. “But the second best time is now.” jBy Rodrigo Pérez OrtegaBIOMEDICINEMicrobiome data dominated by wealthy countries
Skew could hamper development of targeted therapies
2010 2012 2014 2016 2018 20200100200300400Cumulative samples (thousands)02467.Population (billions)2019Oceania
Northern Africa and western Asia
Central and southern Asia
Australia and New Zealand
Latin America and the Caribbean
Sub-Saharan Africa
Eastern and Southeast Asia
Europe, Canada, and the U.S.Missing microbes
To understand how microbes that live on and in us affect health, researchers sequence
their DNA. But most of the world’s people are underrepresented in the data.NEWS | IN DEPTH