by In 2010, a beekeeper in Brooklyn, New York, noticed something weird: his bees were starting to produce red honey. And not just rust red, but a shocking shade of scarlet.
It became known as the red honey mystery, and a clue to the answer, says Kevin Slavin, an independent researcher formerly at the Massachusetts Institute of Technology, came when investigators realized there was a maraschino cherry plant. about a mile from the hives. . It turned out that the bees were stealing the syrup from the plant and the dye used in making maraschino cherries was making its way into their honey.
This was, of course, a problem for the beekeeper (maraschino honey would taste horrible), but years later Slavin and other researchers wondered if it would be possible to take advantage of the behavior of foraging bees to use them to probe urban environments in a way that was not possible before.
Bees, of course, are only interested in collecting materials useful to bees. “But in the meantime,” says Slavin, “they also pick up everything they touch.”
In an article in last week’s issue of Environmental microbiomea team led by Slavin and Dr. Elizabeth Hénaff of New York University’s Tandon School of Engineering, collected samples of rooftop hives not only in New York, but also in Tokyo, Venice, Sydney and Melbourne, in order to see what they might reveal about the urban microbiota.
We usually think of the microbiome in terms of the human microbiome, the collection of microbes living inside and on us. But, says Hénaff, “the human microbiome interacts with the environmental microbiome. It is therefore important to be able to characterize the microbiomes of the cities in which we live, work and sleep.
“The human microbiome interacts with the environmental microbiome. It is therefore important to be able to characterize the microbiomes of the cities in which we live, work and sleep.
Elisabeth Henaff
Historically, she says, the best tool for doing this has been the swab — something that years of COVID-19 have made many of us uncomfortable with. But you can’t dab everything. And in addition to microbes living on various surfaces, there’s also what microbial ecologist Professor Jack Gilbert of the University of California, San Diego has dubbed “the microbial cloud” in the air surrounding everything. that we meet.
Hives are home to tens of thousands of bees, usually foraging over distances of one to three kilometers – flying swabs that not only crawl into all sorts of nooks and crannies, but obligingly carry back to the hive any microorganisms that ‘they inadvertently collected along the way. Including those of the microbial clouds they passed through.
Hénaff and Slavin’s team initially assumed that the best place to look for traces would be in honey. After all, maraschino honey had been loaded with the red dye used in maraschino cherries.
Bees are flying swabs that not only crawl into all sorts of nooks and crannies, but obligingly bring back into the hive any microorganisms they have inadvertently collected along the way.
But when it comes to microorganisms, it turns out that it doesn’t work. Instead, the team discovered that bees are very good at warding off unwanted microorganisms. Instead, they tend to shake them up with other debris they’ve collected along the way.
Slavin has an appropriate analogy. “It’s as if when the bees come home, they wipe their feet on the carpet,” he says. Except that in this case, rather than accumulating on the doormat, the debris falls to the bottom of the hive, forming a thin layer of fine particles, which the researchers were able to collect via specially installed bins.
One of the first findings, according to Hénaff, was that different cities do have distinct microbial signatures and that these show up in materials collected by bees.
Different cities do have distinct microbial signatures and these show up in the materials collected by the bees.
“For example,” she says, “in Venice, one of the main species we found was fungi linked to wood rot – which makes sense because Venice is built on decaying pylons. And in Japan , we found the species responsible for the fermentation products [such as soy sauce]. So it didn’t seem disjointed from all the other things we know about these cities, their culture and their history.
For some reason, however, the Sydney samples were full of a bacteria known to degrade rubber.
Slavin and Hénaff didn’t give an explanation for this, but maybe their Sydney hive was near a big pile of old tires. One of the goals of the study, they say, is to find a way to determine how the microbiome varies not just from city to city, but in different parts of the same city. “Does it change from East London to West London?” Slavine asks. “Does it change block by block?” For now, no one knows.
“The goal is more to understand the extent of the diversity of microbiomes we interact with in urban environments.”
Elisabeth Henaff
It is also of interest to use bees to monitor the prevalence of human pathogens and to test detected pathogens for genes related to their virulence.
This is exactly what the researchers did in Tokyo, where, by chance, they detected Rickettsia felis. Unfortunately, they muddled their finding by incorrectly referring to it as the pathogen that causes cat scratch fever (it’s actually a flea-borne pathogen transmitted by cat fleas that causes a form of spotted fever), but the key point is that they weren’t just able to identify it, but to measure its virulence to humans.
Read more: Varroa – and the threat of bee decimation – has now arrived. What have we learned from the devastation of other nations?
Not that the authors are specifically interested in pathogen surveillance. “The goal is more to understand the extent of the diversity of microbiomes we interact with in urban environments,” says Hénaff. “Most of the microbes that exist are not pathogenic. Many are beneficial to human health, and even more are neutral from our point of view, but can be very important for other species.
In fact, she says, a growing body of research shows that exposure to various microbiomes is important for health, especially for children in urban settings, where more natural microbiomes might be excluded. For example, she says, one study found that when outdoor playground flooring was replaced with synthetic materials over wood chips, the resulting diversification of the microbiome was associated with improved health. children who used it.
“Exposure to various environmental microbiomes is a key component of environmental justice.”
Elisabeth Henaff
“Exposure to various environmental microbiomes is a key component of environmental justice,” she says, adding that from an urban planning perspective, one of the main goals of the study was to find a way to quantify that.
Gilbert (who was not part of the study team) warns, however, that there is still a long way to go before any of the study’s goals can be achieved.
For starters, he says, “if you wanted to prove that bees could be used to monitor the environment for microbial diversity or pathogens, then you would set up a series of microbial markers within a two-mile radius and determine the ability of the hive to “collect” these signals. If you wanted to prove a link between detected [pathogens] and health, you would need to perform an epidemiological analysis at the same time.
There is still a long way to go before any of the study’s objectives can be achieved.
Hénaff agrees that this type of benchmarking – what other fields of research would call “ground-truthing” – is a problem. This is, in fact, exactly the kind of challenge public health officials faced when they first started using wastewater to track the spread of diseases like COVID-19 (and more recently, polio). .
“We thought about this for a long time,” she says.
In the meantime, the next time you see a bee buzzing around you, don’t panic. It might just be monitoring the health of your microbial cloud.
