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An individualized trail of germs is left by each person
Last reviewed: 02.07.2025
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Scientists have recently discovered that bacteria not only live on or inside a person, they also surround them with an invisible cloud. They have also found that everyone has their own unique set of bacteria, and traces of them remain in the air for several hours after the person has left.
Bacteria, both beneficial and harmful, are constantly in close contact with humans, living inside and on the surface of the body, and they are all very important for health and perform certain functions. Thanks to bacteria, the normal functioning of the digestive system is ensured, the body's immune defense is increased.
Eight years ago, the Human Microbiome Project was launched in the United States to thoroughly study bacteria that live in interaction with humans. The project involved 200 healthy people, from whom scientists took samples of microorganisms from different parts of the body and internal organs.
It turned out that a person carries more than 10 thousand types of bacteria, mostly useful or harmless. But pathogenic bacteria are also in close contact with the human body, for example, Staphylococcus aureus was present in the nasal cavity, which, when the immune system is weakened, provokes the development of bilateral pneumonia (was detected in 30% of the participants).
Six years ago, scientists compiled a map of the habitat of microorganisms on the human body. This work showed that the largest number of bacteria live in the nasal cavity, ear canals, hair, lower intestine, feet and palms, and the smallest number in the oral cavity.
American specialists from the University of Oregon decided to determine whether bacteria live around humans.
Several years ago, James Meadow and his colleagues conducted 2 experiments involving 11 people (20-32 years old) who did not suffer from any chronic diseases. For 4 months before the start of the experiment, the participants were prohibited from taking medications.
During the experiments, the participants had to be in a ventilated room (in the first case, air came from the adjacent room, in the second - from the street, while the air passed through small purification systems).
In the first case, each participant sat in the room for 4 hours, then left briefly and returned again for 2 hours. In the second, participants were allowed into the room for 1.5 hours 3 times.
After each exit of the room, air samples were taken, as well as dust from the surface and walls, table, chairs, etc. (specialists entered the room in special sterile suits). In total, more than 300 samples were taken, in which thousands of bacteria in a variety of combinations (more than 14 million options) were identified.
In the first case, scientists wanted to know whether there are microorganisms around a person and whether they remain in the air.
It turned out that each person has an individual set of bacteria that hovered in the ventilated room for 4 hours after the "host" left it. The microbial cloud mainly consists of lactobacilli, lactobacilli, peptostreptococci, streptococci, bifidobacteria, staphylococci.
Scientists also found that the traces of bacteria can be used to determine gender, for example, a large number of lactobacilli were found in the female microbial cloud. Such results of the first experiment forced scientists to conduct a second one, in which they wanted to establish how individual the cloud surrounding a person is.
After the second experiment, the scientists accurately determined which trace was left by which participant. At the same time, the scientists emphasized that the same bacteria surround all people, but the ratio of these bacteria is unique for each person.
James Meadow noted that when they began the experiments, they assumed that there would be microbes around a person, but the fact that such a trace could be used to establish a person's identity was a complete surprise.
Experts are confident that this work will be useful not only from a medical point of view, but may also help forensic scientists in the future.
Now the research needs to be continued, scientists are sure, since there are doubts about whether it is possible to identify the microbial trace of a specific person if there were several people in the room.
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