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For photosynthesis, one photon is all it takes.

Only a single particle of light is required to spark the first steps of the biological process that converts light into chemical energy, scientists report June 14 in Nature.

While scientists have long assumed that the reactions of photosynthesis begin upon the absorption of just one photon, that hadn’t yet been demonstrated, says physical chemist Graham Fleming, of the University of California, Berkeley. He and colleagues decided “we would just look to see was it really true that one photon was enough to start the whole thing off.”

The sunlight that falls on Earth’s surface seems brilliant to human eyes. But on small scales, that translates to a dribble of photons. Only a few tens of photons of the appropriate wavelengths of sunlight fall on a square nanometer per second, the scale of the tiny chlorophyll and bacteriochlorophyll molecules that are central to photosynthesis in plants and bacteria.

Many laboratory experiments on photosynthesis use lasers, much more powerful light sources, to kick off the reactions. Instead, Graham and colleagues used a source of light that produces just two photons at a time. One photon served as a herald, going off to a detector to let researchers know when two photons were released. The other photon went into a solution containing photon-absorbing structures from the photosynthetic bacterium Rhodobacter sphaeroides. These structures, called light-harvesting 2 complexes, or LH2, are made up of two rings of bacteriochlorophyll and other molecules.

In a normal photosynthesis reaction, LH2 absorbs a photon and passes its energy to another LH2 complex, and then another, like a game of hot potato. Eventually the energy reaches another type of ring, called the light-harvesting 1 complex, or LH1, which then passes it to the reaction center where the energy is finally converted into a form that the bacterium can use.

In the experiment, there was no LH1, so the LH2 instead emitted a photon of a different wavelength than the first, a sign that energy had been transferred from the first ring of LH2 to the second, a first step of photosynthesis. The researchers detected that second photon, and by comparing the detection times to those of the initial herald photons, confirmed that the LH2 needed to absorb only one photon to kick things off.

Plants and bacteria use different processes for photosynthesis, but the initial steps are similar enough that in plants, too, a single photon would set off the initial steps, Fleming says. However, in plants, multiple independently absorbed photons are needed in order to complete the reaction.

The role of single photons isn’t surprising, says biochemist Richard Cogdell of the University of Glasgow in Scotland. The important thing the researchers have done, he says, is to demonstrate the new technique. “By doing this you’re able to essentially interrogate what will be happening in nature,” he says.  

Some scientists suspect that photosynthesis relies on quantum physics (SN: 2/3/10). While it’s not clear whether the new technique could resolve the role of quantum effects, it could help scientists disentangle natural effects from artifacts of using intense sources of light in studies of photosynthesis.

“You can really work out what’s happening in the early reactions in photosynthesis as it were outside,” says Cogdell, “[as if] you could shrink yourself down and watch these photons moving around.”

Heating an insecticide can give it new life.

Microwaving the insecticide deltamethrin rearranges its crystal structure but doesn’t change its chemical composition. The rearrangement renews deltamethrin’s ability to kill mosquitoes that have become resistant to the insecticide, researchers report April 21 in Malaria Journal.

The researchers didn’t set out to revive insecticides, says Bart Kahr, a crystallographer at New York University. He and colleagues had been working on crystal growth experiments. “And it turns out that a very good crystal for the experiment that we wanted to do was DDT, the very old, notorious insecticide from the last century.” The researchers realized that DDT has two crystal forms, one of which works better than the other.

They then started experimenting with deltamethrin, an insecticide that is commonly used against mosquitoes that can carry malaria. The chemical is often incorporated into bed nets or sprayed on walls or other surfaces in homes. Mosquitoes absorb the insecticide when they come in contact with it. Kahr and colleagues previously discovered that heating deltamethrin changed its crystal structure, which let it work faster (SN: 10/19/20).

Altering the arrangement of crystals is a tried-and-true way of giving drugs new and different properties, Kahr says. But no one had thought to rearrange insecticide crystals to give them new life, he says. “We just were surprised at how relevant it really was, and a little surprised that nobody has looked at this before,” he says. “Different communities of scientists just have different urgencies. And sometimes when you come from the outside, you look at things from a completely different way.”

Kahr’s team heated a chalk formulation of deltamethrin called D-Fense Dust either in an oven or in a microwave. In the oven, the researchers could precisely control the temperature, he says. “But just for kicks, we said because this deltamethrin is a consumer product, what if you just pop it in the microwave for five minutes? Does that achieve the same thing as heating it to a prescribed temperature in the oven?” The microwave worked just as well, but Kahr cautions that people shouldn’t use the same microwave for heating food and insecticides.

Previously, the researchers had tested the heated deltamethrin crystals on mosquitoes that were already sensitive to the insecticide. In the new study, the scientists teamed up with entomologists to test the heated crystals on five strains of Anopheles mosquitoes from West Africa that are resistant to deltamethrin. In all cases, the rearranged crystals killed the resistant mosquitoes.

That’s important because insecticide resistance is a growing problem and is impairing the ability to control mosquito populations to tamp down malaria spread, says Janet Hemingway, a geneticist at the Liverpool School of Tropical Medicine in England who was not involved in the new study. “We’re now at the point where almost nowhere in Africa is fully susceptible.”

It is encouraging that heated insecticide killed highly resistant mosquitoes, says Hemingway, who directs the Infection Innovation Consortium, a public-private effort to find new ways to combat infectious diseases. But, she says, “this is not something we can take and use that tomorrow.”

For instance, insecticide-treated bed nets are made by mixing deltamethrin with fibers before yarn is extruded. The insecticide migrates to the outside of the yarn and forms crystals. Depending on the manufacturer, “the crystal structures that end up on the surfaces of those bed nets can be quite different,” Hemingway says.

It’s not certain that the heat-treated deltamethrin would retain its more potent crystal structure through the net-making process. And you couldn’t just pop bed nets in the microwave to rearrange the deltamethrin crystals, she says. “You’d need some pretty big microwaves given these things come in shipping containers.”

Kahr’s team is working on incorporating the heat-treated crystal into nets. Liquid sprays are out since the rearranged crystals don’t retain their structure when mixed into water. People could spray the heated chalk instead, but few people would probably want chalky walls, Kahr says. “There are all kinds of social and cultural things that you could propose from a scientific perspective that wouldn’t be welcomed by a community of homeowners.”

The adage “all attention is good attention” may be true for marketers — not so for the Sonoran Desert toad. Last fall, the U.S. National Park Service sent out a message on Facebook asking visitors to “refrain from licking” the toad (technically Incilius alvarius but commonly called Bufo alvarius). That message came months after a New York Times article covered the booming interest in the psychedelic compound that the toad excretes from its skin — along with the “poaching, over-harvesting and illegal trafficking” that have accompanied that interest.

People don’t typically lick the toads to get high, says Robert Villa, a community outreach specialist at the University of Arizona’s Desert Laboratory on Tumamoc Hill. The secretions the toads produce are toxic when ingested. They “work orally, through the mucous membranes, and cause really dangerous side effects, like cardiac arrest,” Villa says.

Instead, for decades, people have been collecting the secretions, then drying and smoking them. When inhaled, a compound within, 5-MeO-DMT, can cause auditory and visual hallucinations. “It’s a very powerful psychedelic sometimes called the ‘God molecule,’ ” says pharmacologist and chemist David Nichols of Purdue University in West Lafayette, Ind.

The drug’s growing popularity could be bad news for toad populations. “If you relocate it outside of its home territory,” Villa says, which often happens when people collect a toad for its secretions, “it gets lost and its chances for survival go way down.” What’s more, collecting large numbers of toads increases the risk of disease transmission, like chytrid fungus, between toads.

We at Science News heard the PSA loud and clear: Just leave this toad alone. But we couldn’t help but wonder: What other amazing animals may have psychedelic potential? Join us on a tour, by land and sea, of some of the world’s mind-altering fauna.

Sonoran Desert toad (Incilius alvarius)

Habitat: The Sonoran Desert, in the southwestern United States and northern Mexico

All toads secrete toxins from their skin. These secretions, whose specific compounds vary from species to species, probably evolved as a way to keep a toad’s body moist. Over time, the compounds, which can also act on the brain and affect heart muscle when ingested, came to aid in self-defense.

But the Sonoran Desert toad, also known as the Colorado River toad, appears to have taken evolution one step further.

The toad, one of the largest in North America, secretes an enzyme that converts bufotenine, a compound also made by other toads, into 5-MeO-DMT, a powerful hallucinogen related to the psychedelic drug DMT.

A frightened Sonoran Desert toad gushes its toxic mix, which includes 5-MeO-DMT, from its parotoid glands — located behind each eye — and from glands on its legs. It’s a way to say, “Please don’t eat me! I don’t taste good!” When swallowed in large quantities by a potential predator, the toxins can cause coma, cardiac arrest and even death.

Scientists aren’t yet sure why the Sonoran Desert toad produces 5-MeO-DMT, and why it is the only toad known to make it. “There’s a lot of mystery,” Villa says.

Giant monkey frog (Phyllomedusa bicolor)

Habitat: The Amazon Basin in South America

There’s no scientific consensus on whether kambô, the name for the toxic secretion produced by the giant monkey frog, should be considered a psychedelic. The term psychedelic comes from Greek meaning “mind manifesting,” Nichols says. “You can imagine, it’s enhancing the properties of your mind, rather than just intoxicating you.” Other compounds such as stimulants and depressants modify the activity of the brain, but they don’t leave users with the kind of new insights and memorable experiences that come with psychedelics.

Wuelton Monteiro, a tropical medicine researcher at the Universidade do Estado do Amazonas in Manaus, Brazil, points to a 2020 study in Scientific Reports as an example of why the classification has been unclear. In the small study, nearly half of participants who reported using kambô said they had a spiritual experience, and some experiences came with what resembled the afterglow often associated with hallucinogens. But kambô doesn’t activate the 5-HT2A receptor, a protein that senses the chemical messenger serotonin, while classic psychedelics do.

Among Indigenous populations in the southwestern Amazon, the frog’s skin secretions have been used for centuries as a stimulant in shamanistic rituals. According to Villa, the secretions are usually applied on small, superficial burns on the body to increase the stamina of hunters.

In predators attempting to gobble the frog, kambô might cause regurgitation, seizures and a change in heart function. Researchers are still trying to decipher the specific compounds that explain these effects, but they do know that species of Phyllomedusa collectively produce over 200 short protein fragments that can influence body function. Some might be promising for future medicines.

California harvester ant (Pogonomyrmex californicus)

Habitat: Southwestern United States and northern Mexico

The venom of the California harvester ant is made up of enzymes that aren’t known to cause hallucinations on their own, but the Indigenous peoples of central California once ate them during rituals including vision quests. Ethnographic reports suggest people would swallow hundreds of live ants in balls of eagle down feathers. No doubt the people were stung, likely on the insides.

Justin Schmidt, an entomologist at the Southwestern Biological Institute and University of Arizona in Tucson who died in February, said the pain of being stung by so many ants, along with extreme cold, fasting and in some cases sleep deprivation, triggered hallucinations that connected the people with spiritual guides.

A harvester ant’s sting is “nothing like a bee sting,” Schmidt wrote in The Sting of the Wild (SN: 8/6/16, p. 26). “The pain is intense, comes in waves, and is deeply visceral.” Lasting from four to eight hours, the pain is accompanied by a numb sensation at the site of the sting. The ants deliver stings to defend their colonies from large predators, including lizards, birds and people. (Smaller enemies such as other insects and spiders are bitten.)

A person who eats 1,000 ants would probably die; according to Schmidt’s book, one ant is enough to kill a mouse. But some predators have defenses: The regal horned lizard (Phrynosoma solare) has a mucus lining its mouth and digestive system that allows it to eat hundreds of ants and a substance in its blood that neutralizes the venom. Some birds somehow avoid getting stung too.

It’s hard to get more information on how the ants were used in rituals and the nature of the experience. Disease and violence that came with Westerners during California’s gold rush destroyed the Indigenous communities in the Central Valley and their way of life.

Salema (Sarpa salpa)

Habitat: Temperate and tropical ocean waters, from the Atlantic coast of Africa to the Mediterranean Sea

Fishes including this species of sea bream, as well as some sea chubs and clownfish, can cause auditory and visual hallucinations when eaten, though reports are rare. Sarpa salpa was known as the “dream fish” in ancient Rome, according to a 2018 review of psychedelic fauna published in Frontiers in Psychiatry. Two cases of hallucinatory fish poisoning were documented in 2006 in the journal Clinical Toxicology. In one case, a 40-year-old man ate baked S. salpa and later experienced hallucinations of screaming animals and giant arthropods surrounding his car. The symptoms went away, with medical attention, 36 hours after he ate the fish.

Researchers don’t know what compounds cause this ichthyoallyeinotoxism, or fish poisoning, which can include nightmares. Evolutionary biologist Leo Smith of the University of Kansas in Lawrence, who studies fish history and diversification, says he and other scientists suspect that the compounds are a by-product of the fishes’ diets.

But ichthyoallyeinotoxism is distinct from two other forms of fish poisoning. Symbiotic bacteria within puffer fish produce a neurotoxin called tetrodotoxin, or TTX, that can cause paralysis and death. And ciguatera fish poisoning comes from eating fish contaminated with a neurotoxin produced by some dinoflagellates. It can cause diarrhea, vomiting and weakness, as well as a reverse sensory disruption, where hot things seem cold and vice versa. But it does not cause hallucinations, says Sandric Leong, a biological oceanographer at the National University of Singapore.

How and why many of these neurotoxins are produced is still being worked out. “There are so many relationships with the marine environment which we are not very sure of,” Leong says.

Pitted sponge (Verongula rigida)

Habitat: The Caribbean

The pitted sponge and some other sponges including Smenospongia aura and S. echina contain 5-bromo-DMT and 5,6-dibromo-DMT. Because of their relationship with the psychedelic drug DMT, these compounds are plausible psychedelics. American chemist Alexander Shulgin, famous for his research into psychedelic compounds and for introducing the world to the synthetic hallucinogen MDMA, or ecstasy, and his wife Ann Shulgin wrote in TIHKAL: The Continuation that they don’t know whether the sponge compounds are activated by smoking or not. They are, however, “quantitatively reduced to DMT by stirring under hydrogen in methanol, in the presence of palladium on charcoal.”

The pitted sponge is known to concentrate in its tissue chemicals called monoamines that can modify the behavior of nerve cells. Not only can these compounds make the sponge taste bitter, but they can also alter the behavior of predatory fish that dine on the sponge.

“They wouldn’t prevent the fish from ever trying to take a bite, but it would prevent it from persisting or consuming the sponge any beyond an initial several bites,” says Mark Hamann, a pharmacologist from the Medical University of South Carolina in Charleston.

V. rigida’s ability to alter animal behavior intrigued Hamann, who reported in a 2008 study in the Journal of Natural Products that 5,6-dibromo-DMT acted like an antidepressant in rats, while 5-bromo-DMT acted like a sedative. Hamann says that related compounds may one day be isolated and might make for promising antidepressants, anxiety-reducing drugs or pain relievers in people.

Millions of years ago, giant volcanic eruptions in what’s now Turkey and Peru each deposited millions of metric tons of nitrate on the surrounding land. That nutrient may have come from volcanic lightning, researchers reported April 24 at a meeting of the European Geosciences Union in Vienna.

The discovery adds evidence to the idea that, early in Earth’s history, volcanoes could have provided some of the materials that made it possible for life to emerge, says volcanologist Erwan Martin of Sorbonne University in Paris.

Nitrogen is an essential ingredient in biological molecules, such as proteins and DNA. It makes up about 78 percent of the atmosphere. But nitrogen molecules in the air consist of two tightly bound nitrogen atoms. Only when these atoms are separated will they react with other elements and create forms of nitrogen useful to life, such as nitrate (SN: 4/8/08).

Some microbes can tease apart the nitrogen molecules and provide “fixed nitrogen” to plants and fungi. Human chemists can do it too, creating fertilizer. But before life could start, some nonbiological process must have been at play.

Lightning is the obvious candidate, Martin says. These extremely energetic electric discharges can tear apart nitrogen atoms, which will combine with oxygen to form nitrogen oxides and eventually nitrate.

The lightning in thunderstorms, brought about by ice particles colliding and charging, separates nitrogen molecules every day, but at low rates and spread out over large areas. Volcanic plumes, in which dust particles do the colliding and charging, can provide localized lightning at staggering intensities. During one day of the 2022 eruption of the Hunga Tonga-Hunga Ha’apai volcano in Indonesia, for instance, there were about 400,000 discharges (SN: 12/13/22).

Even that large amount of lightning creates a relatively small amount of nitrate. But rare, huge eruptions, of the kind that happen only every 100,000 years or so, could create much more. The idea that such events could produce and deposit a lot of nitrate is not new, Martin says, but until now nobody had actually looked at the nitrogen content of volcanic deposits from these eruptions.

His group sampled outcrops in Turkey and Peru linked to 10 explosive eruptions that happened between 20 million and 1 million years ago. Their locations’ relatively dry climate helps ensure that any nitrate formed long ago, which is soluble in water, would not have all leached out by now.

The nitrate that the researchers found turns out to contain oxygen atoms with different masses, in a proportion similar to that of the three oxygen atoms that make up each molecule of ozone in the air. This shows that the nitrates were formed in the atmosphere and not by some process on the ground, the team says.

Based on their sampling, the researchers estimate that each eruption on average deposited about 60 million tons of nitrate.

Life may have begun roughly 3.7 billion years ago, long before the eruptions that Martin and colleagues studied (SN: 3/1/17). But Earth’s early years were full of such extreme volcanism. Some researchers think that lightning over volcanic islands, in particular, played a role in the emergence of life, before even the continents were fully formed. On the young Earth, Martin says, similar amounts of nitrate as those estimated in the new study could have been produced on such islands, long since submerged.

The study’s concept is interesting, says marine chemist Jeffrey Bada of the Scripps Institution of Oceanography in La Jolla, Calif. But he thinks the researchers should have addressed the different composition of the atmosphere at the time that life first came on the scene.

“In today’s world, lightning on volcanic islands produces copious amounts of nitrogen oxides,” Bada says. “But in the early Earth, when the atmosphere had little oxygen in it, the product would have been probably ammonia.” Like nitrate, ammonia is a form of nitrogen that’s biologically usable.

But, Martin says, in a volcanic plume, there is a lot of water and other oxygen compounds coming from the magma, which could have supplied some of that oxygen. And in those early days, he says, “maybe it wasn’t nitrate but ammonia — it’s still nitrogen available for life. These are still things that need to be studied.”