Rutgers professor discovers that bacteria may be able to travel around the world via air
Research conducted by a Rutgers professor suggested that bacteria may not only travel globally by hitchhiking off of hosts such as humans, but also by traveling through the air.
The concept of “hitchhiking” on host organisms is a well-known concept. Dr. Konstantin Severinov, a principal investigator at Waksman Institute of Microbiology and senior author of the study, said the spread of antibiotic resistance around the world has mostly been associated with people traveling and being in contact with others.
“You hear a story of a person in the nearest hospital dying from a nasty infection and often it turns out that person visited this or that faraway country, so that the presumption is that people with certain microbes in certain places will become vehicles to transport these bacteria around the world. So you can imagine that a people-mediated spread is a large factor in bacteria ecology,” he said.
The new hypothesis of bacteria traveling through air came from collecting samples of thermophiles, a type of bacteria that grows in temperatures hotter than 150 degrees Fahrenheit around the world.
“These are bugs that require higher temperatures for growth," Severinov said. “They live in hot springs at neutral pH, in water (which) is not boiling but is on the hotter end.”
The study used thermophiles specifically because they were easy to find since they occupied such a hostile environment. As opposed to more hospital environments like human intestines, hot springs have a lower diversity of bacteria, Severinov said.
Although the exact mechanism of how they might travel through the air remains largely unknown, research has shown clear signs of travel. Severinov said researchers found that bacteria living in hot springs in Chile, Italy and Russia — countries that were thousands of miles apart — showed signs that they came from the same origin.
These signs of global travel are known as “molecular memories,” or pieces of viruses left over from previous infections in a bacteria’s DNA. These remnants of DNA are stored in a specific DNA sequence, known as CRISPR, and are passed to the bacteria’s future offspring.
To explain this observation, the bacteria in different hot springs either changed their genetic makeup, or more plausibly, traveled from one site to another. For thermophilic bacteria, sometimes the land around them is too cold for them to continue growing. Severinov said some hypotheses for traveling included underground channels, but this was not supported by ideas in geology.
Another hypothesis was that, since these bacteria were so tiny, they actually were able to be lifted up into the air by wind so that they could be deposited in faraway places, where the conditions would be more suitable for them to grow.
“We compared these memories of thermophiles from different places, and the argument would have been if bacteria living in these remote places would have been experiencing different viruses, then their CRISPR memories would have been different. But what we found was that there was a lot of commonality,” Severinov said. “We therefore had to conclude that this could have happened through global transfer from one hot spring to another.”
Bacteria might not be able to survive long outside their preferred environments, but the air movement around the globe is fast enough for them to live throughout their travel.
“The air I breathe out right now in Europe can get recycled to New Jersey in about a week or less,” Severinov stated.
His research, while still a hypothesis and only involving one type of bacteria, can have implications for the field of epidemiology if it is proven to be a significant way to spread bacteria. For the future, he said there needs to be a more international effort of sampling air at different altitudes, as well as sites around the globe to observe the bacteria there.
“The infrastructure to test this hypothesis will need a large effort and does not fall on any one country to conduct it,” Severinov said.