Microbes are transmitted between people and the environment in two ways. First, by touch. When you pick up an object and pass it to your friend, you give them a sampling of the microbes on your hands. (Remember your mom always telling you to wash your hands?) In addition to transmission by direct contact, microbes can become airborne and travel through the environment by a process that remains poorly understood.
James Meadow, a microbial ecologist at the University of Oregon, reasoned that our personal microbes could be transmitted in the form of a microbial cloud, and that the microbial “fingerprint” of this cloud would differ from person to person.
To test this hypothesis, Meadow and colleagues looked for microbial clouds emitted by eleven human subjects. They collected air from a chamber after occupants had spent between two and four hours inside. To determine if any microbes fell to the ground during that time, they also collected samples from settling dishes placed under each occupant.
To identify specific bacteria, the team sequenced 16S rRNA genes (this gene codes for a subunit of the ribosome and is often used to identify bacteria). Meadow detected microbial clouds only when the test subjects occupied the chamber. Although, not all subjects shed significant amounts of bacteria into the settling dishes. Meadow detected a number of bacterial species associated with various environments. Among them were species of Corynebacterium and Staphylococcus usually associated with skin, Anaerococcus found in the lungs, Lactobacillus from the vagina, and Stenotrophomonas and Citrobacter from soil and aquatic sources.
The most surprising finding was that subjects could actually be distinguished based on the microbes that made up their microbial clouds. That is, each person had a slightly unique cloud (for example, only female subjects were associated with species of Lactobacillus, which is commonly found in the vagina).
These findings raise an interesting question. Could microbial clouds be used to place suspects at the scene of a crime? According to Meadow, “there are a lot of reasons why we might want to know if some nefarious character’s been in a certain room in the last few hours...maybe there’s a way to use microbes for that”.
Sources: PeerJ, New Scientist, NPR, NIH, Wikipedia