Instead of hitching a ride on people or animals, some bacteria may travel thousands of miles through the air, according to a new study.
This “air bridge” hypothesis could shed light on how harmful bacteria share antibiotic resistance genes, researchers say.
“Our research suggests that there must be a planet-wide mechanism that ensures the exchange of bacteria between faraway places,” says senior author Konstantin Severinov, a principal investigator at the Waksman Institute of Microbiology and professor of molecular biology and biochemistry at Rutgers University-New Brunswick.
“Because the bacteria we study live in very hot water—about 160 degrees Fahrenheit—in remote places, it is not feasible to imagine that animals, birds, or humans transport them,” Severinov says. “They must be transported by air and this movement must be very extensive so bacteria in isolated places share common characteristics.”
For the study, which appears in Philosophical Transactions of the Royal Society B, Severinov and other researchers studied the “molecular memories” of bacteria from their encounters with viruses, with the memories stored in bacterial DNA.
Bacteriophages—viruses of bacteria—are the most abundant and ubiquitous forms of life on the planet, and have a profound influence on microbial populations, community structure, and evolution, according to the study.
The scientists collected heat-loving Thermus thermophilus bacteria in hot gravel on Mount Vesuvius and hot springs on Mount Etna in Italy; hot springs in the El Tatio region in northern Chile and southern Chile’s Termas del Flaco region; and hot springs in the Uzon caldera in Kamchatka, Russia.
In virus-infected bacterial cells, molecular memories store in special regions of bacterial DNA called CRISPR arrays. Cells that survive infections pass the memories—small pieces of viral DNA—to their offspring. The order of these memories allows scientists to follow the history of bacterial interaction with viruses over time.
Initially, the scientists thought that bacteria of the same species living in hot springs thousands of miles apart—and therefore isolated from each other—would have very different memories of their encounters with viruses. That’s because the bacteria all should have independent histories of viral infections.
The scientists also thought that bacteria should evolve very rapidly and become different, much like the famous finches Charles Darwin observed on the Galapagos Islands.
“What we found, however, is that there were plenty of shared memories—identical pieces of viral DNA stored in the same order in the DNA of bacteria from distant hot springs,” Severinov says.
“Our analysis may inform ecological and epidemiological studies of harmful bacteria that globally share antibiotic resistance genes and may also get dispersed by air instead of human travelers.”
The scientists want to sample air at different altitudes and locations around the world and identify the bacteria there to test the air bridge hypothesis. They would need access to planes, drones, or research balloons.
Additional scientists from the Russian Academy of Sciences; Skolkovo Institute of Science and Technology in Russia; Pasteur Institute in France; University of Santiago de Chile; and Weizmann Institute of Science in Israel contributed to the work.
Source: Rutgers University