WASHINGTON, D.C. — Whether it is a jungle hut or a high-rise apartment, your home is covered in bacteria. That is not always a bad thing. However, new research from the Amazon rain forest suggests city dwellers might want to open a window.
Learning About Microbes
Scientists traveled through South America, from remote villages in Peru to a large Brazilian city, to track one of the unseen effects of urbanization. Over time, more and more people have moved to urban areas like cities. Many things change as new buildings arise and more people live in a small area of land. This study focused on how urbanization affects the diversity of bacteria inside people's homes.
The study is a small first step in a larger quest to understand how different environmental bugs help shape what's called our microbiome. Microbiomes are the collections of bacteria and other tiny microbes that live inside our bodies. These trillions of bacteria share our bodies and play a critical role in our health.
"Very little is known about the microbes of the built environment," according to microbiologist Maria Gloria Dominguez-Bello. She is a professor at New York University, and led the study in South America.
The Walls Have Germs
Her team found that as people in the Amazon rain forest come to live in larger villages and cities the kinds of bacteria in their homes change. They lose the bugs mostly found in nature and pick up those that typically live on people.
In fact, in city dwellings, the researchers could tell just by the bacteria on the walls that "this is a kitchen or this is a bathroom or this is a living room. That's amazing," Dominguez-Bello said.
As she puts it, "the walls talk."
Everyone carries a customized set of bacteria on the skin, in the nose and in the gut. This bacteria starts accumulating at birth and helps with such things as digestion and the immune system, which fights off colds and disease. What influences the balance of good bugs and bad varies depending on such things as your diet, how you were born, and what antibiotic medicines you take. Environmental exposures play a role, too.
One Theory Of Allergies
For example, one theory suggests asthma and allergies are on the rise in Western populations because kids get less contact with bugs that were once common in their surroundings. This theory may be one reason why children who grow up on farms or around animals tend to have fewer of those immune-related illnesses.
Increasingly, scientists also are investigating where we spend a lot of time, especially our homes. To track the effects of urbanization, Dominguez-Bello's team studied the bacterial communities of 10 houses and their inhabitants from four different locations. Three of these were in Peru: a village of hunter-gatherers, a slightly more modern rural village and the medium-sized city of Iquitos. The fourth location was Manaus, a larger city in Brazil.
These locations gave the scientists the opportunity to compare similar people living in four different states of urbanization. Peru and Brazil are neighboring countries in South America. Each includes large sections of the Amazon rain forest. The people living in the two small villages are relatively similar to those living in Iquitos (population about 150,000) and Manaus (population about 2,000,000).
Bad Germs: Gone With The Wind?
Housing styles help tell the story, said study co-author Humberto Cavallin, an architect at the University of Puerto Rico. Large families shared open-air jungle huts with no outside walls. Homes in the rural villages had indoor walls but they did not reach the roof. City homes were larger with standard rooms and smaller families.
Despite having fewer people living in them, it was the city dwellings that had the most human bacteria living on their walls and floors, the researchers reported. In Manaus, bacteria normally found in the mouth and in the gut were the most important in telling rooms apart. The more crowded jungle and village homes were filled with bacteria commonly more found in soil and water than with human microbes.
The walls of city homes were acting as traps and retaining the bacteria that people shed. This was especially true when compared with the village homes that allowed air to circulate more freely, the team reported. Dominguez-Bello was so struck by the findings that she insisted the windows in her New York office be unsealed so she could open them.
A Balancing Act
She next will compare the microbiomes of the residents with their homes. However, she did acknowledge that there is a balancing act to this. While jungle and village homes may allow for more air to move within them, these have their own set of problems. For example, many of these homes do not have screens to keep out disease-carrying mosquitoes.
Still, the findings reflect research in U.S. homes and hospitals about the role of ventilation, said Jack Gilbert of the University of Chicago. He is a microbiologist who was not involved in the study. His own housing study was able to match which family lived where by the bacteria they shed inside.
He said that when it comes to studying microbiomes and bacteria, "our modern homes are set up perfectly."
Questions:
1. How did Maria Gloria Dominguez-Bello make her discovery about bacteria?
2. According to the study, what is the connection between urbanization and bacteria?
3. Why did village homes have less human bacteria than city homes?
4. Microbiomes are the collections of bacteria and other tiny microbes that live inside our bodies. These trillions of bacteria share our bodies and play a critical role in our health.
Which word would BEST replace "critical" in this sentence without changing its meaning?
A. minor
B. important
C. negative
D. mysterious
5. The walls of city homes were acting as traps and retaining the bacteria that people shed.
What is the BEST definition of "retaining" as used above?
A. to clean something
B. to harm something
C. to transform something
D. to hold on to something
6. Based on your understanding, define the word "antibiotic".
