It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Chemists have demonstrated the synthesis of a new molecular form of carbon.
The new molecule – cyclo[48]carbon, made up of 48 carbon atoms in an alternating single/triple bond pattern – is stable enough to be studied in liquid solution form at room temperature.
The study – only the second example of a new type of molecular carbon allotrope that can be studied under normal laboratory conditions – has been published today (14 August) in Science.
In a new study led by Oxford University’s Department of Chemistry, chemists have demonstrated the synthesis of a cyclocarbon that is stable enough for spectroscopic characterisation in solution at room temperature.
The synthesis of a new type of molecular carbon allotrope that can be studied under normal laboratory conditions is a rare achievement. The only previous example was the synthesis of fullerenes by Krätschmer et al. in 1990 (Nature 1990).
In the new study, the molecule cyclo[48]carbon was synthesised as a [4]catenane, i.e. with the C48 ring threaded through three other macrocycles. These threaded macrocycles increase the stability of C48 by preventing access to the protected cyclocarbon.
Previously, molecular rings consisting purely of carbon atoms have only been studied in the gas phase or at very low temperatures (4 to 10 K). Now, the team have synthesised a cyclocarbon that is stable in solution at 20°C (half-life 92 hours). This has been achieved by using threaded macrocycles, choosing a large cyclocarbon with a low level of strain, and developing mild reaction conditions for the unmasking step in the reaction (where a precursor molecule is transformed into the final product).
The cyclocarbon catenane was characterised by mass spectrometry, NMR, UV-visible and Raman spectroscopy. The observation of a single intense 13C NMR resonance for all 48 sp1 carbon atoms indicates that all of the carbons are in equivalent environments, which provides strong evidence for the cyclocarbon catenane structure.
Lead author Dr Yueze Gao (Department of Chemistry, University of Oxford) said: “Achieving stable cyclocarbons in a vial at ambient conditions is a fundamental step. This will make it easier to study their reactivity and properties under normal laboratory conditions.”
Study senior author Professor Harry Andersen (Department of Chemistry, University of Oxford) said: “This achievement marks the culmination of a long endeavour to synthesise cyclocarbon catenanes, based on the hope that they might be stable enough to study at room temperature. The original grant proposal was written in 2016, based on preliminary results from 2012–2015. It is satisfying to have reached this point, because there were many times when the goal seemed unrealistic and unachievable. This work would not have been possible without the outstanding facilities for NMR spectroscopy in the Department of Chemistry at Oxford.”
The study ‘Solution-phase stabilization of a cyclocarbon by catenane formation’ will be published in Science at 19:00 BEST / 14:00 ET on Thursday 14 August at https://doi.org/10.1126/science.ady6054
Advance copies of the paper may be obtained from the Science press package, SciPak, at https://www.eurekalert.org/press/scipak/ or by contacting scipak@aaas.org
Space-filling representation of cyclo[48]carbon [4] catenane. Credit: Harry Anderson.
Credit
Harry Anderson.
D.E.I.
From left to right: Study authors Prakhar Gupta, Yueze Gao, and Harry Anderson holding a model of part of the catenane. Credit: Dr Robert Eichelmann.
An electron microscope image of single-celled methanogens, members of the archaea branch of the tree of life. They are ubiquitous in oxygen-free environments, turning simple foods into methane, a potent greenhouse gas.
Roughly two-thirds of all emissions of atmospheric methane — a highly potent greenhouse gas that is warming planet Earth — come from microbes that live in oxygen-free environments like wetlands, rice fields, landfills and the guts of cows.
Tracking atmospheric methane to its specific sources and quantifying their importance remains a challenge, however. Scientists are pretty good at tracing the sources of the main greenhouse gas, carbon dioxide, to focus on mitigating these emissions. But to trace methane’s origins, scientists often have to measure the isotopic composition of methane's component atoms, carbon and hydrogen, to use as a fingerprint of various environmental sources.
A new paper by researchers at the University of California, Berkeley, reveals how the activity of one of the main microbial enzymes involved in producing methane affects this isotope composition. The finding could change how scientists calculate the contributions of different environmental sources to Earth's total methane budget.
"When we integrate all the sources and sinks of carbon dioxide into the atmosphere, we kind of get the number that we're expecting from direct measurement in the atmosphere. But for methane, large uncertainties in fluxes exist — within tens of percents for some of the fluxes — that challenge our ability to precisely quantify the relative importance and changes in time of the sources," said UC Berkeley postdoctoral fellow Jonathan Gropp, who is first author of the paper. "To quantify the actual sources of methane, you need to really understand the isotopic processes that are used to constrain these fluxes."
Gropp teamed up with a molecular biologist and a geochemist at UC Berkeley to, for the first time, employ CRISPR to manipulate the activity of this key enzyme to reveal how these methanogens interact with their food supply to produce methane.
"It is well understood that methane levels are rising, but there is a lot of disagreement on the underlying cause," said co-author Dipti Nayak, UC Berkeley assistant professor of molecular and cell biology. "This study is the first time the disciplines of molecular biology and isotope biogeochemistry have been fused to provide better constraints on how the biology of methanogens controls the isotopic composition of methane."
Many elements have heavier or lighter versions, called isotopes, that are found in small proportions in nature. Humans are about 99% carbon-12 and 1% carbon-13, which is slightly heavier because it has an extra neutron in its nucleus. The hydrogen in water is 99.985% hydrogen-1 and 0.015% deuterium or hydrogen-2, which is twice as heavy because it has a neutron in its nucleus.
The natural abundances of isotopes are reflected in all biologically produced molecules and variations can be used to study and fingerprint various biological metabolisms.
"Over the last 70 years, people have shown that methane produced by different organisms and other processes can have distinctive isotopic fingerprints," said geochemist and co-author Daniel Stolper, UC Berkeley associate professor of earth and planetary science. "Natural gas from oil deposits often looks one way. Methane made by the methanogens within cow guts looks another way. Methane made in deep sea sediments by microorganisms has a different fingerprint. Methanogens can consume or ‘eat’, if you will, a variety of compounds including methanol, acetate or hydrogen; make methane; and generate energy from the process. Scientists have commonly assumed that the isotopic fingerprint depends on what the organisms are eating, which often varies from environment to environment, creating our ability to link isotopes to methane origins.”
"I think what's unique about the paper is, we learned that the isotopic composition of microbial methane isn’t just based on what methanogens eat," Nayak said. “What you ‘eat’ matters, of course, but the amount of these substrates and the environmental conditions matter too, and perhaps more importantly, how microbes react to those changes."
"Microbes respond to the environment by manipulating their gene expression, and then the isotopic compositions change as well," Gropp said. "This should cause us to think more carefully when we analyze data from the environment."
The paper will appear Aug. 14 in the journal Science.
Vinegar- and alcohol-eating microbes
Methanogens — microorganisms that are archaea, which are on an entirely separate branch of the tree of life from bacteria — are essential to ridding the world of dead and decaying matter. They ingest simple molecules — molecular hydrogen, acetate or methanol, for example — excreted by other organisms and produce methane gas as waste. This natural methane can be observed in the pale Will-o'-the-wisps seen around swamps and marshes at night, but it's also released invisibly in cow burps, bubbles up from rice paddies and natural wetlands and leaks out of landfills. While most of the methane in the natural gas we burn formed in association with hydrocarbon generation, some deposits were originally produced by methanogens eating buried organic matter.
The isotopic fingerprint of methane produced by methanogens growing on different “food” sources has been well established in laboratory studies, but scientists have found that in the complexity of the real world, methanogens don't always produce methane with the same isotopic fingerprint as seen in the lab. For example, when grown in the lab, species of methanogens that eat acetate (essentially vinegar), methanol (the simplest alcohol), or molecular hydrogen (H2) produce methane, CH4, with a ratio of hydrogen and carbon isotopes different from the ratios observed in the environment.
Gropp had earlier created a computer model of the metabolic network in methanogens to understand better how the isotope composition of methane is determined. When he got a fellowship to come to UC Berkeley, Stolper and Nayak proposed that he experimentally test his model. Stolper’s laboratory specializes in measuring isotope compositions to explore Earth's history. Nayak studies methanogens and, as a postdoctoral fellow, found a way to use CRISPR gene editing in methanogens. Her group recently altered the expression of the key enzyme in methanogens that produces the methane — methyl-coenzyme M reductase (MCR) — so that its activity can be dialed down. Enzymes are proteins that catalyze chemical reactions.
Experimenting with these CRISPR-edited microbes — in a common methanogen called Methanosarcina acetivorans growing on acetate and methanol — the researchers looked at how the isotopic composition of methane changed when the enzyme activity was reduced, mimicking what is thought to happen when the microbes are starved for their preferred food.
They found that when MCR is at low concentrations, cells respond by altering the activity of many other enzymes in the cell, causing their inputs and outputs to accumulate and the rate of methane generation to slow so much that enzymes begin running both backwards and forwards. In reverse, these other enzymes remove a hydrogen from carbon atoms; running forward, they add a hydrogen. Together with MCR, they ultimately produce methane (CH4). Each forward and reverse cycle requires one of these enzymes to pull a hydrogen off of the carbon and add a new one ultimately sourced from water. As a result, the isotopic composition of methane's four hydrogen molecules gradually comes to reflect that of the water, and not just their food source, which starts with three hydrogens.
This is different from typical assumptions for growth on acetate and methanol that assume no exchange between hydrogen derived from water and that from the food source.
"This isotope exchange we found changes the fingerprint of methane generated by acetate and methanol consuming methanogens vs. that typically assumed. Given this, it might be that we have underestimated the contribution of the acetate-consuming microbes, and they might be even more dominant than we have thought," Gropp said. "We're proposing that we at least should consider the cellular response of methanogens to their environment when studying isotopic composition of methane."
Beyond this study, the CRISPR technique for tuning production of enzymes in methanogens could be used to manipulate and study isotope effects in other enzyme networks broadly, which could help researchers answer questions about geobiology and the Earth's environment today and in the past.
"This opens up a pathway where modern molecular biology is married with isotope-geochemistry to answer environmental problems," Stolper said. "There are an enormous number of isotopic systems associated with biology and biochemistry that are studied in the environment; I hope we can start looking at them in the way molecular biologists now are looking at these problems in people and other organisms — by controlling gene expression and looking at how the stable isotopes respond."
For Nayak, the experiments are also a big step in discovering how to alter methanogens to derail production of methane and redirect their energy to producing useful products instead of an environmentally destructive gas.
"By reducing the amount of this enzyme that makes methane and by putting in alternate pathways that the cell can use, we can essentially give them another release valve, if you will, to put those electrons, which they were otherwise putting in carbon to make methane, into something else that would be more useful," she said.
Other co-authors of the paper are Markus Bill of Lawrence Berkeley National Laboratory and former UC Berkeley postdoc Rebekah Stein, and Max Lloyd, who is a professor at Penn State University. Gropp was supported by a fellowship from the European Molecular Biology Organization. Nayak and Stolper were funded, in part, by Alfred B. Sloan Research Fellowships. Nayak also is an investigator with the Chan-Zuckerberg Biohub.
An electron microscope image of single-celled methanogens, members of the archaea domain. They are ubiquitous in oxygen-free environments, turning simple foods into methane, a potent greenhouse gas.
Modulation of methyl-coenzyme M reductase expression alters the isotopic composition of microbial methane
Article Publication Date
14-Aug-2025
Researchers track how iron deficiency disrupts photosynthesis in crucial ocean algae
Rutgers marine scientists use tools created in New Jersey to quantify how iron stress in Southern Ocean phytoplankton slows the process of converting light energy into oxygen
Rutgers graduate student Heshani Pupulewatte (at right in yellow hard hat) collects water samples measuring conductivity, temperature and depth on a research ship in the Southern Atlantic Ocean.
Credit: Brandy Robinson/ GEOMAR Helmholtz Centre for Ocean Research Kiel
The next time you breathe, consider this: photosynthesis of algae, powered by iron dust in the ocean, made it possible.
Now, a new Rutgers University study published in the Proceedings of the National Academy of Sciences pulls back the curtain on this vital process.
Iron is a critical micronutrient for marine phytoplankton, the microscopic algae that form the foundation of the ocean’s food webs. It is deposited into the world’s oceans as dust from deserts and arid areas as well as from glacial meltwater.
“Every other breath you take includes oxygen from the ocean, released from phytoplankton,” said Paul G. Falkowski, the Bennett L. Smith Chair in Business and Natural Resources at Rutgers-New Brunswick and a co-author of the study. “Our research shows that iron is a limiting factor in phytoplankton’s ability to make oxygen in vast regions of the ocean.”
When iron is absent or reduced, photosynthesis – the process of turning light energy into chemical energy, with oxygen as a byproduct – is slowed or halted. This limits the growth of these organisms and affects how efficiently they capture sunlight and remove carbon dioxide from the atmosphere.
Evidence suggests climate change is altering patterns of ocean circulation and reducing iron deposition, Falkowski said. While humans can still breathe easily – reduced iron levels in the world’s oceans won’t mean that humans will suffocate – the trend could have significant effects on marine life, he said.
“Phytoplankton are the primary source of food for krill, the microscopic shrimp that are the main source of food in the Southern Ocean for virtually every animal, including penguins, seals, walruses and whales,” Falkowski said. “When iron levels drop and the amount of food available for these upper-level animals is lower, the result will be fewer of these majestic creatures.”
Researchers have long suspected that iron is crucial to photosynthesis, but little is known about how the process is affected in nature. Most previous studies have been conducted only in the laboratory.
To address this gap, Heshani Pupulewatte, a graduate research assistant in the Department of Chemistry and Chemical Biology conducting research in Falkowski’s lab and lead author of the study, spent 37 days in 2023 and 2024 aboard a British research vessel sailing through the South Atlantic Ocean and Southern Ocean, covering a transect from the South African coast to the marginal ice zone of the Weddell Gyre and back.
Using custom fluorometers built by Max Gorbunov from the Falkowski Lab on Cook Campus in New Brunswick, Pupulewatte tested samples for fluorescence – a measure of energy re-released by phytoplankton when the photosynthesis process breaks down. She then added nutrients to samples collected along the route to determine if doing so could restart the photosynthesis process.
“We wanted to know what really happens to the energy transfer process at the molecular level of phytoplankton in natural environments,” she said.
What she found was that iron limitation causes up to 25% of light-harvesting proteins to become “uncoupled” from the energy-producing centers, effectively reducing energy conversion. When iron is resupplied, phytoplankton reconnect their internal light-harvesting systems, improving their efficiency and potential for growth.
“We demonstrated the results of iron stress on phytoplankton out in the ocean, without even bringing back samples to the lab to perform molecular extractions using fluorescence measurements carried out at sea,” she said. “By doing so we were able to show that much more energy is wasted as fluorescence when iron is limiting.”
Understanding how iron influences photosynthesis at the molecular level could help scientists predict future ocean productivity and global carbon cycles, she added.
The discovery of yet another unique animal species from Rēkohu Chatham Islands illustrates how the physical qualities of an animal are influenced by its surroundings.
New research led by the University of Otago – Ōtākou Whakaihu Waka describes a new, extinct shelduck whose ancestors arrived on the islands 390,000 years ago.
While this may seem like a short period of time, co-lead author Associate Professor Nic Rawlence, Director of the Otago Palaeogenetics Laboratory, says it is long enough to impact the species.
“In that time the Rēkohu shelduck evolved shorter, more robust wings and longer leg bones indicating it was going down the pathway towards flightlessness,” he says.
These changes were due to a range of factors, such as an abundance of food, lack of ground-dwelling predators, and windy conditions, so flying was not the preferred option.
Co-lead author Dr Pascale Lubbe, also of the Otago Palaeogenetics Laboratory, says in a case of “use it or lose it, the wings start to reduce”.
“Flight is energetically expensive, so if you don’t have to fly, why bother,” she says.
“The longer leg bones are more robust to support more muscle and create increased force for take-off – necessary when you have smaller wings.”
Researchers used ancient DNA and analysed the shape of the bones to determine the Rēkohu shelduck is most closely related to the pūtangitangi paradise shelduck from Aotearoa New Zealand.
The Rēkohu shelduck spent more time on the ground than its cousin and became extinct prior to the 19th century due to over-hunting and predation.
The study is published in the Zoological Journal of the Linnean Society and adds to the islands’ rich history as a home to many species of waterfowl before human settlement.
The shelduck’s scientific name (Tadorna rekohu) and common name (Rēkohu shelduck) were gifted to researchers by the Hokotehi Moriori Trust who are tchieki (guardians) of the plants and animals on Rēkohu Chatham Islands, with which they are interconnected through shared hokopapa (genealogy).
Hokotehi Moriori Trust CEO Levi Lanauze says “this discovery is great for Rēkohu as a whole and helps connect imi (tribe) Moriori with miheke (treasure) of the past”.
The study is an international collaboration between Otago, the Museum of New Zealand Te Papa Tongarewa, The University of Adelaide, and Manaaki Whenua Landcare Research.
CHICAGO — August 14, 2025 — The 66th Supplement to the American Ornithological Society’s (AOS’s) Check-list of North American Birds, published today in Ornithology, includes several significant updates to the classification of bird species found in North America, Central America, and the Caribbean.
A few highlights from the supplement, detailed below, include species splits for Myiarchus nuttingi, Vireo gilvus, and Larus argentatus; the addition of subfamilies in the Laridae for white-terns and noddies; and a merging of three families of Caribbean nine-primaried oscines.
The Check-list, published since 1886, is updated in annual supplements from the AOS’s North American Classification Committee (NACC). The Check-list and its supplements provide the taxonomic and nomenclatural foundation for bird research, conservation, management, and education throughout the region, and are relied on as the authority on avian biodiversity by government agencies, NGOs, scientists, and birders, among others. The NACC reviews proposals submitted annually for taxonomic and distributional updates to the Check-list of North American Birds.
Until recently, it was thought that the Nutting’s Flycatcher (Myiarchus nuttingi) complex consisted of three subspecies: M. n. inquietus in western Mexico, and M. n. nuttingi and M. n. flavidior in Middle America. An analysis of hundreds of sound recordings of these subspecies, among other data, resulted in a species split and elevation to species status for M. flavidior, now called Salvadoran Flycatcher. In their proposal (2025-A-4), authors Roselvy Juárez, John van Dort, and Oscar Johnson stated, “The two taxa are sympatric in multiple locations with no sign of interbreeding, have diagnostic songs that are as different as those between other species of Myiarchus, and occupy different habitats across a broad swath of Central America.”
“The vocal differences were quantified nicely,” Chesser remarks. “and the fact that there’s no evidence of interbreeding where these species co-occur clinched the argument for species status.”
Get ready to add a new vireo species to your checklist! NACC co-chair Carla Cicero submitted a proposal (2025-C-3) to elevate different subspecies of Vireo gilvus (Warbling Vireo) to species status. As it turns out, the Eastern (gilvus) subgroup and the Western (swainsoni) subgroups “are separate species based on differences in a suite of characters, including genetics, vocalizations, and molt and migration; importantly, these differences are maintained where they breed parapatrically,” says Chesser. These species breed assortatively where they meet, despite low levels of hybridization. Vireo swainsoni is now the Western Warbling-Vireo, and V. gilvus is now the Eastern Warbling-Vireo.
Despite some striking morphological similarities, hawks within the genus Accipiter have been found through new molecular evidence not to comprise a monophyletic group, as documented in a proposal (2025-C-1) from Shawn M. Billerman. He proposed a new generic arrangement of species within the family Accipitridae, including adding two new genera to the Check-list. Notably, this revision resulted in the transfer of Accipiter cooperii (Cooper’s Hawk) and several other hawks from Accipiter into the newly recognized genus Astur. This might be surprising to birders, considering the striking morphological similarities between A. cooperii, which is now in Astur, and A. striatus (Sharp-shinned Hawk), which will remain in Accipiter. “People have trouble telling Cooper’s and Sharp-shinned Hawks apart, but it turns out that they’re not that closely related,” Chesser remarks. “Raptors in general show a lot of convergence, and it turns out that the harriers are actually more closely related to species of Astur than Astur and Accipiter are to each other.” Other hawk species moved to Astur include A. gundlachi (Gundlach’s Hawk), A. bicolor (Bicolored Hawk), A. gentilis (Eurasian Goshawk), and A. atricapillus (American Goshawk), and A. soloensis (Chinese Sparrowhawk) has been transferred to the genus Tachyspiza.
The large, complex family Laridae has undergone some significant changes at several taxonomic levels as a result of two proposals (2025-C-2 and 2025-A-3). Within the long-confounding genus Larus, which includes the large white-headed gulls, L. argentatus (formerly Herring Gull) has been split into four species based on an array of genetic, phenotypic, ecological, and vocal differences: L. argentatus (now European Herring Gull), L. vegae (Vega Gull), and L. smithsonianus (American Herring Gull) as well as the extralimital L. mongolicus. Chesser explains more about the challenges within this group, saying, “They are closely related, recently separated, and they also hybridize. That presents a confusing genetic signature, but they do not appear to be each other’s closest relatives, certainly not as a group.”
Also within the Laridae, the subfamily Sterninae has been significantly revised because some species have been shown to be more divergent from other terns than previously thought, based on a proposal (2025 A-3) by H. Douglas Pratt and Eric VanderWerf, with contributions from the late Storrs Olson. Notably, birds of the genera Gygis (white-terns) and Anous (noddies) have been moved from the Sterninae into their own new subfamilies, Gyginae and Anoinae, respectively. “We thought the white-terns and noddies were closely related to each other and to other terns,” Chesser explains, “but they’re actually all quite distinct.” In addition, based largely on morphology, vocalizations, and, in one case, archeological evidence of historical sympatry, G. candida (Blue-billed White-Tern) and G. microrhyncha (Little White-Tern) have been separated as new species from G. alba (now called Atlantic White-Tern).
Family Mergers
Merger for three families of Caribbean nine-primaried oscines
A proposal (2025-C-11) from Kevin J. Burns led to the merging of two families of Caribbean nine-primaried oscines into a third family, the Phaenicophilidae, which is now named the Greater Antillean Tanagers and comprises two subfamilies and nine species. Data from multiple molecular phylogenetic studies provided evidence that these species constitute a monophyletic group resulting from an endemic Caribbean radiation, facts highlighted by the new family classification. Species originally in the family Phaenicophilidae are also now placed in the subfamily Phaenicophilinae (Hispaniolan Tanagers) and those originally in the families Nesospingidae and Spindalidae now constitute the subfamily Spindalinae (Puerto Rican Tanagers and Spindalises).
About the journal
The journal Ornithology is a peer-reviewed, international journal of ornithology published by the American Ornithological Society (AOS). Ornithology (formerly The Auk) commenced publication in 1884 under the banner of the American Ornithologists’ Union, the AOS’s predecessor society. In 2009, Ornithology was honored as one of the 100 most influential journals of biology and medicine over the past 100 years.
About the American Ornithological Society
The American Ornithological Society (AOS) is an international society dedicated to connecting ornithologists, science, and bird conservation by supporting science that advances the understanding and conservation of birds; promoting broad access to ornithological science; supporting ornithologists throughout their career paths; and fostering a welcoming, diverse, supportive, and dynamic ornithological community. The AOS publishes two top-ranked international scientific journals, Ornithology and Ornithological Applications, and hosts an annual conference that attracts ornithologists from across the globe. Its robust grants program supports student and early-career professional research initiatives. The society’s check-lists serve as the accepted authorities for scientific nomenclature and English common names of birds in the Americas. The AOS is also a partner with The Cornell Lab of Ornithology in the online Birds of the World, a rich database of species accounts of the world’s birds. The AOS is a 501(c)(3) nonprofit organization serving about 3,000 members globally. For more information, see www.americanornithology.org.
