Science
Louis Pasteur’s Relentless Hunt for Germs Floating in the Air
Louis Pasteur was at his most comfortable when working in his Paris laboratory. It was there that he had some of his greatest scientific triumphs, including experiments that helped confirm germs can cause disease. “Everything gets complicated away from the laboratory,” he once complained to a friend.
But in 1860, years before he became famous for developing vaccines and heating milk to kill pathogens, Pasteur ventured to the top of a glacier, on a remarkable quest for invisible life.
He and a guide began at the base of Mont Blanc in the Alps, hiking through dark stands of pines. Behind them, a mule carried baskets of long‑necked glass chambers that sloshed with broth. They ascended a steep trail until they reached Mer de Glace, the sea of ice.
The wind blew briskly over the glacier, and the vale echoed with the sound of frozen boulders crashing down the slopes. Pasteur struggled to make out the path in the glare of sunlight bouncing off the ice.
When the scientist reached an altitude of 2,000 meters, he finally stopped. He removed one of the glass chambers from the mule’s pack and raised it over his head. With his free hand, he grabbed a pair of tongs and used them to snap off the end of the neck. The cold air rushed inside the container.
The sight of Pasteur holding a globe of broth over his head would have baffled other travelers visiting Mer de Glace that day. If they had asked him what he was doing, his answer might have seemed mad. Pasteur was on a hunt, he later wrote, for “the floating germs of the air.”
Now, 165 years later, scientists around the world hunt for floating germs. Some study how coronaviruses wafting through buses and restaurants spread Covid. Spores of fungi can travel thousands of miles, infecting people and plants. Oceans deliver microbes into the air with every crashing wave. Even clouds, scientists now recognize, are alive with microbes.
The sky’s ecosystem is known as the aerobiome. In Pasteur’s day, it had no name. The very idea of living things drifting through the air was too strange to imagine.
But Pasteur began to wonder about the possibility of airborne life when he was a little-known chemist teaching at the University of Lille in France. There, the father of one his students approached him for help. The man owned a distillery where he used yeast to turn beet juice into alcohol. But the juice had inexplicably turned rancid.
Inspecting the liquid under a microscope, Pasteur discovered dark rods — bacteria rather than yeast — in the sour vats. The discovery helped him work out a theory of fermentation: Microorganisms absorbed nutrients and then produced new compounds. Depending on the species, they could turn butter rancid or grape juice into wine.
The discovery won Pasteur a prestigious new post in Paris. In his account of the discovery, Pasteur suggested in passing that the bacteria might have floated through the air and settled into the vats. That notion earned him an angry letter from Félix‑Archimède Pouchet, one of France’s leading naturalists.
Pouchet informed Pasteur that the microorganisms Pasteur discovered had not dropped into the vats from the air. Instead, the beet juice had spontaneously generated them. “Spontaneous generation is the production of a new organized being that lacks parents and all of whose primordial elements have been drawn from ambient matter,” Pouchet had written earlier.
Pasteur coolly replied that Pouchet’s spontaneous generation experiments were fatally flawed. The conflict between Pasteur and Pouchet prompted the French Academy of Sciences to announce a contest for the best study addressing whether spontaneous generation was real or not. What started as a private spat had turned into a public spectacle. Pasteur and Pouchet both signed up to compete for the prize of 2,500 francs.
The public eagerly followed the competition, struggling to imagine either view of life. Spontaneous generation had the whiff of blasphemy: If life could spring into existence, it did not require divine intervention. But Pasteur’s claim that the atmosphere teemed with germs also strained the 19th‑century mind. A French journalist informed Pasteur that he was going to lose the contest. “The world into which you wish to take us is really too fantastic,” he said.
To prove that his world was real, Pasteur set out to pluck germs from the air. Working with glassblowers, he created flasks with narrow openings that stretched for several inches. He filled them with sterile broth and waited to see if anything would grow inside. If the necks were pointed straight up, the broth often turned cloudy with microorganisms. But if he sloped the necks so that the openings pointed down, the broth stayed clear. Pasteur argued that germs in the air could drift down into the flasks, but could not propel themselves up a rising path.
When Pouchet heard about Pasteur’s experiments, he sneered. Did Pasteur really believe that every germ in decaying organic matter came from the air? If that were true, every cubic millimeter of air would have been packed with more germs than all the people on Earth. “The air in which we live would almost have the density of iron,” Pouchet said.
Pasteur responded by changing his hypothesis. Germs were not everywhere, he said. Instead, they drifted in clouds that were more common in some places than others.
To prove his claim, Pasteur took his straight-necked flasks out of his lab and began collecting germs. In the courtyard of the Paris Observatory, all 11 of his flasks turned cloudy with multiplying germs. But when he traveled to the countryside and ran his experiment again, more of his flasks stayed sterile. The farther Pasteur got from human settlements, the sparser airborne life became. To put that idea to an extreme test, Pasteur decided to climb Mer de Glace.
His first foray to the glacier ended in failure. After holding up a flask, he tried using the flame from a lamp to seal its neck shut, but the glare of the sun made the flame invisible. As Pasteur fumbled with the lamp, he worried that he might be contaminating the broth with germs he carried on his skin or his tools. He gave up and trudged to a tiny mountain lodge for the night.
He left his flasks open as he slept. In the morning they were rife with microorganisms. Pasteur concluded that the lodge was packed with airborne germs that travelers had brought from around the world.
Later that day, Pasteur modified his lamp so that the flame would burn bright enough for him to see it under the glacier-reflected sun. When he climbed back up Mer de Glace, the experiment worked flawlessly. Only one of the flasks turned cloudy with germs. The other 19 remained sterile.
In November 1860, Pasteur arrived at the Academy of Sciences in Paris with the 73 flasks he had used on his travels. He entered the domed auditorium, walked up to the table where the prize committee sat, and laid out the flasks. The judges peered at the broth as Pasteur described his evidence, saying it gave “indubitable proof” of floating germs in inhabited places.
Pouchet refused to accept the evidence, but nevertheless withdrew from the contest. Pasteur was awarded the prize.
Still, the two continued to spar. The rivalry remained so intense that the Academy set up a new commission to evaluate their latest experiments. Pouchet dragged out the proceedings, demanding more time for his research.
Pasteur decided to seize public opinion and put on a spectacle. On the evening of April 7, 1864, in an amphitheater filled with Parisian elites, Pasteur stood surrounded by lab equipment and a lamp to project images on a screen. He told the audience it would not leave the soiree without recognizing that the air was rife with invisible germs. “We can’t see them now, for the same reason that, in broad daylight, we can’t see the stars,” he said.
At Pasteur’s command, the lights went out, save for a cone of light that revealed floating motes of dust. Pasteur asked the audience to picture a rain of dust falling on every surface in the amphitheater. That dust, he said, was alive.
Pasteur then used a pump to drive air through a sterile piece of cotton. After soaking the cotton in water, he put a drop under a microscope. He projected its image on a screen for the audience to see. Alongside soot and bits of plaster, they could make out squirming corpuscles. “These, gentlemen, are the germs of microscopic beings,” Pasteur said.
Germs were everywhere in the air, he said — kicked up in dust, taking flights of unknown distances and then settling back to the ground, where they worked their magic of fermentation. Germs broke down “everything on the surface of this globe which once had life, in the general economy of creation,” Pasteur said.
“This role is immense, marvelous, positively moving,” he added.
The lecture ended with a standing ovation. Pasteur’s hunt for floating germs elevated him to the highest ranks of French science.
By the time he died 31 years later, Pasteur had made so many world-changing discoveries that his many eulogies and obituaries did not mention his trip to Mer de Glace.
But scientists today recognize that Pasteur got the first glimpse of a world that they are only starting to understand. They now know that life infuses the atmosphere far more than he had imagined, all the way to the stratosphere. Our thriving aerobiome has led some scientists to argue that alien aerobiomes may float in the clouds of other planets. Ours is not the only world that seems too fantastic to believe.
Science
Identity first, or person first? Guidelines this series follows when writing about autism and mental health
Autism and mental health are complex subjects. Here are some guidelines we use when choosing how to write about them.
Person first? Identity first? It depends.
When we’re writing about a person’s experience with a mental health condition, we’ll likely use “person-first language.” For example, we will refer to someone as “living with schizophrenia” or “having a diagnosis of schizophrenia,” instead of describing that person as “a schizophrenic.”
The same goes for writing about a disability, which is a mental or physical condition that significantly affects the ability to carry out at least one life activity. An illness or disability is something that a person has, not the essence of who they are.
When it comes to autism, many people with the neurodevelopmental condition prefer what’s called “identity-first language”: describing someone as “an autistic person,” for example, rather than “a person with autism.” Advocates for this language say that autism is an essential part of their identity, and isn’t something that can or should be separated from an individual either in real life or on the page.
Research has found that a majority of autistic people in English-speaking countries prefer identity-first language. Most of the time, that’s what you’ll read in these stories. There are also people in the autism community who prefer person-first language, so there will be times when that’s the more appropriate choice. And of course, when we directly quote someone, we will use the exact words they said or wrote.
In general, when an individual makes clear how they want to be described, we will honor that person’s preferences.
Many autistic people live with mental health conditions. Autism isn’t one of them.
Autism is a neurodevelopmental condition that affects social communication and sensory processing. It’s not a mental health disorder, and isn’t something that can be cured.
Studies have found that up to 80% of adults diagnosed with autism spectrum disorder also have at least one additional mental health condition such as depression or anxiety. These conditions are distinct from autism, and often respond to treatment interventions.
When reporting on suicide, there is some information we leave out on purpose.
Multiple studies have found that certain descriptors and details, particularly those connected to the specific method by which a person died, may have a harmful effect on people struggling with thoughts of suicide. For that reason, our stories don’t describe the methods people use to kill themselves, even when we have learned that information during our reporting.
Language evolves and we will too.
Our stories are based on the best information we have available at the time we publish. When we learn new information that changes our understanding of a subject, the words we use will change as well.
Science
Kratom was linked to 6 L.A. deaths and banned in the county. But the supplement’s actual health risks remain a mystery
Recently, the Los Angeles County Public Health Department reported it had linked the deaths of six L.A. County residents over the last spring and summer to the use of kratom, a widely available but unregulated supplement sold as a remedy for all sorts of health issues.
The deaths prompted public health officials to announce Nov. 7 that they would red-tag and pull from store shelves all products containing either kratom or the synthetic alkaloid 7-Hydroxymitragynine, also known as 7-OH, which is derived from kratom. Both are currently unregulated and not approved for use in the United States or the state of California as a drug product, dietary supplement or an approved food additive, according to the U.S. Food and Drug Administration.
For the record:
10:16 a.m. Nov. 20, 2025A previous version of this article misspelled Dee Macaluso’s last name as Mascalusco.
Unsurprisingly, business owners who sell kratom feel that the health department has overstepped, going too far without understanding how the supplement is helping many L.A. residents. The deaths, they say, are not necessarily due to kratom products, but to interactions with other substances.
Perhaps more important are the benefits that kratom users and some experts claim the drug provides. Many say the problem is with 7-OH — a highly concentrated, synthetic version of natural kratom that is subject to adulteration and fraudulent marketing — and that banning the sale of all kratom products could create an even more dangerous underground market of both kratom and 7-OH.
Indeed, many kratom sellers and users would welcome better regulation, so that they could continue to use the affordable, widely available substance as a way to treat physical pain and mental health issues with more confidence in the efficacy and safety of the products they are selling and buying.
During the months of April and July, a total of six L.A. County adults between the ages of 19 and 39 died with kratom and 7-OH in their bodies, along with other substances including alcohol, prescription sedatives and muscle relaxers, and cocaine.
In the medical examiner’s reports, the cause of death for five of the deceased was listed as a consequence of “mixed drug effects”; the sixth was listed as being caused by an overdose of cocaine.
The Times spoke with three different toxicologists to review these coroner’s reports and get a better understanding of what role kratom or 7-OH may have had in the deaths.
What the experts told The Times is that while toxicologists have an understanding of the possible effect that kratom alone can have on the body, the picture becomes unclear when other drugs are introduced.
Kratom is an herbal extract made from the leaves of Mitragyna speciosa, a tree native to Southeast Asia. It is sold in smoke shops and online in a variety of forms including powders, pills and liquid extracts.
At low doses, kratom causes a stimulant effect with users reporting an uptick in energy. At high doses it creates a sedative effect, said Donna Papsun, a forensic toxicologist with NMS Labs.
Researchers say a majority of kratom users consume the plant to relieve pain. In some cases, people report using it effectively to treat opioid dependence. Others use it to alleviate mental health challenges such as anxiety and depression.
In the last few years, a synthetic version of kratom refined to its psychoactive compound 7-Hydroxymitragynine, or 7-OH, has grown in popularity. The much more potent form of the largely unregulated drug has become a concern for public health officials and advocates.
But toxicologists say there isn’t enough research to provide a comprehensive understanding of what concentrations of kratom or 7-OH can be acutely toxic in the body when alone.
It’s likely they can also cause dangerous reactions when combined with other drugs that could amplify their effects, experts said, but the lack of research means doctors just don’t know what they are. That’s where the most concerning risks lie, said Craig Smollin, medical director of the San Francisco division of the California Poison Control System.
In cases where kratom and 7-OH are found in the bodies of a recent accidental death, typically toxicologists have found evidence of polysubstance use — when two or more drugs are taken together either intentionally or unintentionally.
“I don’t claim to have investigated all the reports about kratom deaths, but I haven’t seen too many reports of single-drug ingestions of kratom causing death,” Smollin said.
And while there’s an effective method to test for the quantity of kratom in the body, there isn’t a similarly accurate test for 7-OH. Current tests can only say whether or not it is present. In all six L.A. County deaths, it was.
But, Papsun notes, when kratom is metabolized in the body, part of the breakdown includes 7-OH, which means it will likely show up in medical exams whenever kratom does.
Toxicology labs face significant challenges when trying to quickly develop tests for emerging drugs like 7-OH for use in post-mortem medical examinations, Papsun said. “Adding something to a scope of testing is not easy from a forensic point of view because you have to develop it, validate the test, have available commercial material and it has to be scientifically rigorous because these results can end up in court,” Papsun said.
A further challenge to testing for 7-OH, specifically, is that the compound is “incredibly unstable,” she said. It can be detected in the body at the time of death but by the time the sample is collected and tested, the compound may have started to break down already, leading to inaccurate results.
Robert Powers, a forensic toxicologist at the University of New Haven, agreed that it was difficult to tell whether kratom and 7-OH played a direct role in the L.A. County deaths. “Most of the problems that arise with this drug are in combination with other respiratory depressant type drugs: opiates, benzodiazepines, alcohol,” he said, though he added that the deaths are “not an easy picture” to understand.
That’s why, he said, the L.A. County health department’s move to pull these products off the shelves makes sense. “I think it’s reasonable to recognize that in these cases, kratom could have indeed played a contributory role. And I understand the interest in trying to limit the potential effects of this drug in those mixed cases, so I understand why people would be interested in controlling this drug.”
Smollin, the San Francisco poison center director, concurred, pointing out how much the county still might not know about kratom and 7-OH.
That lack of information trickles down to consumers, who often rely on guidance from local, state and federal agencies about the risks of products like kratom and 7-OH.
Indeed, Dee Macaluso, 74, said she’s had to take it upon herself to seek out other sources of guidance, and experiment with different amounts of daily dosage to alleviate her symptoms of fatigue and trouble breathing from years of chronic lung illnesses.
When she learned of the county’s decision, “it scared me to death that they were going to pull” kratom products. “I told my husband, I don’t know what I’m going to do if I don’t have it and then I won’t be able to get out of bed, or paint or do the little bit that I can do,” she said.
Macaluso was an actor and comedian who in her 60s lived in Park City, Utah, but more recently moved to L.A. when her health declined due to pneumonia that progressed to debilitating infections in her lungs.
Macaluso used to have an active lifestyle, but the damage to her lungs made it so she could barely go up and down the stairs of her Utah home without feeling winded. She also felt the elevation in Park City was straining her health — it’s one reason she chose to move to Los Angeles, which is mostly low-altitude.
She saw a number of specialists, but none offered any options that helped alleviate her symptoms. Then, she stumbled on a documentary that highlighted the benefits of kratom in regards to chronic pain and mental health. She decided to try it.
“I didn’t use it very often, but when I did I found that it helped so many of my issues,” Macaluso said.
She described the effect as a boost of energy that in turn gave her the motivation and strength to get out of bed. “This was much more of a subtle feeling of just relief from being in a state of someone who is unwell and tired,” Macaluso said. “I loved it and I still use it.”
As her illness has progressed, Macaluso has continued to rely on kratom whenever she knows she’ll have a long day or has to attend a function and be sociable.
“It made me feel like my old self — smart mouth, funny and quick. I was a stand-up comic, I did all these things and I was becoming this old tired lady that got winded going up a few stairs and it pissed me off,” she said.
Macaluso doesn’t advocate for 7-OH but she doesn’t want kratom to be banned; she’d rather it be regulated and available to the public.
“I think the government should give us the leeway to educate ourselves,” she said. ”There’s always going to be people that misuse it but I don’t think that those of us who are using it responsibly and getting benefit from it should be penalized.”
Business owners like Abdullah Mamun, who started the company Authentic Kratom 12 years ago, agree with Macaluso’s perspective.
Authentic Kratom began as an e-commerce business based in Canoga Park, and has since grown into three brick-and-mortar locations in Canoga Park, Woodland Hills and Hollywood.
Mamun believes 7-OH is a real risk, and that L.A. County should focus its efforts there. A blanket ban on all kratom products, however, is counterproductive, he said. First of all, based on what his customers have told him over the past decade or so, he believes “kratom doesn’t cure you, but it gives people the relief that they’re looking for and the ability to manage their pain.” Second, red-tagging kratom products would directly affect his Authentic Kratom and the livelihood of his seven full-time employees.
And he welcomes regulation on kratom products.
“We want them to be properly labeled for customers because people should know what they’re putting in their body,” he said.
Science
Beloved eagle, a school mascot, electrocuted on power lines above Bay Area elementary school
MILPITAS, Calif. — As scores of students swarmed out of their Milpitas elementary school on a recent afternoon, a lone bald eagle perched high above them in a redwood tree — only occasionally looking down on the after-school ruckus, training his eyes on the grassy hills along the western horizon.
The week before, his mate was electrocuted on nearby power lines operated by PG&E.
Kevin Slavin, principal of Curtner Elementary School, said the eagles in that nest are so well-known and beloved here that they were made the school’s mascots and the “whole ethos of the school has been tied around them” since they arrived in 2017.
What exactly happened to send Hope the eagle off the pair’s nest in the dark of night and into the live wires on the night of Nov. 3 is not known (although there’s some scandalous speculation it involved a mysterious, “interloper” female).
According to a spokesperson from PG&E, an outage occurred in the area at around 9 p.m. Line workers later discovered it was caused by the adult eagle.
The death, sadly, is not atypical for large raptors, such as bald and golden eagles.
According to a 2014 analysis of bird deaths across the U.S., electrocution on power lines is a significant cause of bird mortality. Every year, as many as 11.6 million birds are fried on the wires that juice our televisions, HVAC systems and blow driers, the authors estimated. The birds die when two body parts — a wing, foot or beak — come in contact with two wires, or when they touch a wire and ground source, sending a fatal current of electricity through the animal’s body.
Because of their massive size, eagles and other raptors are at more risk. The wingspan of an adult bald eagle ranges from 5.5 to 8 feet across; it’s roughly the same for a golden eagle.
An eagle couple in Milpitas, before the female was electrocuted when coming into contact with high-power electrical lines earlier this month.
(Douglas Gillard)
According to a report from the U.S. Fish and Wildlife Service’s National Forensics Laboratory, which analyzed 417 electrocuted raptors from 13 species between 2000 and 2015, nearly 80 percent were bald or golden eagles.
Krysta Rogers, senior environmental scientist at the California Department of Fish and Wildlife Investigations Laboratory, examined the dead eagle.
She found small burns on Hope’s left foot pad and the back of her right leg. She also had singed feathers on both sides of her body, but especially on the right, where Rogers said the wing looked particularly damaged. She said most birds are electrocuted on utility poles, but Hope was electrocuted “mid-span,” where the wires dip between the poles.
Melissa Subbotin, a spokesperson for PG&E, said the poles and wires near where the birds nested had been adapted with coverings and other safety features to make them safe for raptors.
However, it appears the bird may have touched two wires mid-span. Subbotin said the utility company spaces lines at least 5 feet apart — a precaution it and other utility companies take to minimize raptor deaths.
“Since 2002, PG&E has made about 42,990 existing power poles and towers bird-safe,” Subbotin said. The company has also retrofitted about 41,500 power poles in areas where bird have been injured or killed.
In addition, she said, in 2024, the company replaced nearly 11,000 poles in designated “Raptor Concentration Zones” and built them to avian-safe construction guidelines.
Doug Gillard, an amateur photographer and professor of anatomy and physiology at Life Chiropractic College West in Hayward, who has followed the Milpitas eagles for years, said while there is safety equipment near the school, it does not extend into the nearby neighborhood, where Hope was killed.
Gillard said a photographer who lives in the neighborhood took a photo of the eagle hanging from the wires that Gillard has seen. The Times was unable to access the photo.
Not far from the school is a marshy wetland, where ducks, geese and migrating birds come to rest and relax, a smorgasbord for a pair of eagles and their young. There are also fish in a nearby lake.
Gillard said one of the nearby water bodies is stocked with trout, and that late fall is fishing season for the eagles. He said an army of photographers is currently hanging around the pond hoping to catch a snapshot of the father eagle catching a fish.
Rogers said the bird was healthy. She had body fat, good muscle tone and two small feathers in her gut — presumably the remnants of a recent meal. She also had an enlarged ovary and visible oviduct — an avian fallopian tube — suggesting she was getting ready for breeding, which typically happens in January or February.
Slavin, the principal, said that a day or two before the mother’s death, he saw the couple preparing their nest, and saw a young female show up. “It was a very tense situation among the eagles,” he said.
Gillard, the photographer, said the “girlfriend” has black feathers on her head and in her tail, suggesting she isn’t quite five years old.
Gillard and Slavin say they’ve heard from residents there may have been some altercation between the mom and the interloper that sent Hope off the nest and into the wires that night.
The young female remains at the scene, and is not only being “tolerated” by the father, but occasionally accompanies him on his fishing trips, Gillard said.
Eagles tend to mate for life, but if one dies, the other will look for a new mate, Gillard said. If the female eagle sticks around, it will be the dad’s third partner.
Photographers can identify the father, who neighbors just call “Dad,” by the damaged flexor tendon on his right claw, which makes it appear as if he is “flipping the bird” when he flies by.
-
Science1 week agoWashington state resident dies of new H5N5 form of bird flu
-
Business4 days agoStruggling Six Flags names new CEO. What does that mean for Knott’s and Magic Mountain?
-
New York1 week agoDriver Who Killed Mother and Daughters Sentenced to 3 to 9 Years
-
World1 week agoUnclear numbers: What we know about Italian military aid to Ukraine
-
Politics2 days agoRep. Swalwell’s suit alleges abuse of power, adds to scrutiny of Trump official’s mortgage probes
-
Northeast1 week agoCamelot or Cringe?: Meet JFK’s grandson turned congressional candidate for the scrolling generation
-
Ohio3 days agoSnow set to surge across Northeast Ohio, threatening Thanksgiving travel
-
Southeast1 week agoAlabama teacher arrested, fired after alleged beating of son captured on camera