These gates, called proton-activated chloride channels (PAC), nest within cell membranes and regulate the passage of small molecules called chloride ions into and out of cells. This allows cells to sense and respond to their environment.

“Proton-activated chloride channels have only recently been described but they are critical for cell survival, particularly in the brain,” said Wei Lü, Ph.D., a Van Andel Institute assistant professor and co-corresponding author of the study, which was published today in Nature. “Our new images, coupled with our findings into how these channels work, provide much-needed molecular blueprints that will help answer long-standing questions in the field and provide new insights into how these channels may be therapeutically targeted in disease.”

The images reveal a wedding bouquet-like structure, with parts that change configuration in response to environmental pH. When pH shifts from alkaline to acidic, a key pH sensor moves from its “resting” location and is inserted in an “acidic pocket,” which signals that the gate allowing ions in and out of the cell should be open. This specific mechanism has never before been described.

This study is a collaboration between the Lü Lab at Van Andel Institute and a group led by Zhaozhu Qiu, Ph.D., an assistant professor at Johns Hopkins University School of Medicine and co-corresponding author of the paper. The Johns Hopkins team first reported the discovery of PAC in Science last year.

Solving PAC structures are another important, early step toward an understanding that may one day impact human health.

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When the atoll’s managers — the U.S. Fish and Wildlife Service, The Nature Conservancy and Island Conservation — were planning to conduct a rat eradication project, UC Santa Barbara community ecologist Hillary Young and her research group saw it as an unusual opportunity. They had already been visiting Palmyra regularly to track another non-native species — the coconut palm — to see whether it was spreading invasively in the area, potentially impacting the nesting seabird population and changing the island’s soil composition. They had plots where they were monitoring trees in various stages of growth and survival; how would the vegetation respond to the eradication of the island’s main seed and seedling eater?

“Prior to the eradication, most of the understory of Palmyra was either bare ground — sandy soil or coral rubble — or covered in a carpet of ferns,” said Ana Miller-ter Kuile, a graduate student researcher in the Young Group and lead author of a study that appears in the journal Biotropica. The rats were quick to eat seeds and young plants coming out of the ground, and they frequented the canopy as well, often nesting in the coconut palms and eating coconuts.

Eradication of the rats — which was conducted in 2011 — did in fact result in a resurgence of vegetation on Palmyra. And not only that. The Asian tiger mosquito was wiped out, while two species of land crab emerged, adding to the atoll’s biodiversity.

But rarely is ecology easily untangled. In the years that followed eradication, Palmyra’s understory did indeed fill with juvenile trees as seeds that hit the ground were allowed to take root. Only they were often not the Pisonia or other native trees that would have been the more ideal forests for the native seabirds and animals of Palmyra.

“I was on the island in 2012, just after the eradication and could easily navigate through the open jungle understory,” Miller-ter Kuile said. “Two years later when I went back, I was wading through an infuriating carpet of seedlings that were taller than me, tripping over piles of coconuts.” While the researchers found a 14-fold increase in seedling biomass, most of these new seedlings were juvenile coconut palms, their proliferation left unchecked by the removal of the rats.

“Rats were basically eating almost every nut before it even reached the forest floor,” Miller-ter Kuile said. “I knew that rats could have an impact, I just didn’t expect it to be this large.” In the absence of rats, according to a population model the researchers built based on a decades’ worth of data on coconut seed production, growth and survival, the coconut palms’ population growth rate increased by 10% — enough to eventually overtake the island, had the managers not stepped in with an aggressive coconut palm removal project.

The coconut palm invasion is a problem for places like Palmyra Atoll, as it shifts the island’s ecology away from native plants and animals.

“Coconuts have a very different ‘nutritional’ profile from the native tree species on this island, with much more carbon and less nitrogen,” Miller-ter Kuile said. “When these trees die, because they have different nutrient profiles from native plants, they are likely to break down differently — and more slowly — and influence rates of decomposition.” In addition, she said, native seabirds do not nest in coconut palms, which would deprive the atoll of the nutrients in their guano, which, in turn, “would lead to what would likely be a fairly nutrient-poor system, which discourages other native plants from growing in those areas.”

Continuing their restoration of the island, Palmyra’s managers were working to remove the vast majority of the island’s millions of coconut palms to give local species a chance to dominate, a project that is currently on hold due to the COVID-19 pandemic.

Anticipating the indirect downstream effects, such as potential shifts in ecology toward other invasive species, could become part of a more holistic island rodent eradication effort, Miller-ter Kuile said.

“Wildlife management, in particular, has a history of being single-species focused, which often means that a lot of time and energy is put into producing or controlling a species without considering the broader effects of that management effort on all of the rest of the species in that ecosystem,” she said. According to the study, “documenting the variation in invasive rodent diet items, along with long-term surveys, can help prioritize island eradications where restoration is most likely to be successful.”

“The ‘accidental experiment’ of our long-term monitoring of trees in this project I think provides a rare opportunity to quantify the immediate and longer-term effects of eradication,” she said.

The research, published this week in PLOS ONE, outlines the discovery of DNA evidence of the disease in civilian remains predating WWI by thousands of years. In total, the team analyzed bone fragments and teeth of 145 individuals alive between the 1st and 19th centuries. Approximately 20% of those remains contained traces of Bartonella quintana, the bacteria responsible for trench fever.

Davide Tanasi, an associate professor with USF’s History Department and member of the Institute for the Advanced Study of Culture and the Environment, excavated remains for this project from a Roman cemetery in Syracuse, Sicily. Tanasi, who is also the director of USF’s Institute for Digital Exploration, first began work at the site to better understand the dietary habits and health of the Christian population living there during the 3rd and 4th centuries. Through a collaboration with French epidemiologists, researchers used real-time polymerase chain reaction testing to detect B. quintana DNA within the remains.

“Once contracted, there are diseases, like trench fever, that can leave traces within your DNA and can integrate your DNA with further information,” Tanasi said. “This means that once a person dies, even as far back as 2,000 years ago, it is still possible to find traces of the bacterium that infected them.”

Tanasi says the discovery sheds light on the complex history of trench fever and begins answering historical questions about the lives of Christian citizens in this region during the 3rd and 4th centuries.

“Archaeology isn’t just the study of the past, but it’s something that can make the present better through the study of the past,” he said. “The more we understand about the behavior of these bacteria in the past, the more we can design plans to address them, contain them and eliminate them in the present.”

While most associate this disease with WWI and WWII, occurrences of trench fever are still reported today, most prominently within homeless populations. The bacteria are spread to humans through contact with body lice (Pediculus humanus corporis), making poor personal hygiene a primary factor in its spread and infection rate. Researchers hope that by tracing the progression of B. quintana through history, they’re able to identify ways to better manage the spread of the disease today.

For Tanasi, his work with the remains excavated in Sicily continues. Through stable-isotope analysis, his research group examines the diet and lives of those who once lived in the region. He hopes this work will further answer questions about the lifestyle and health of the Christian community of Roman Syracuse.

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Bioengineers around the world are working to develop plastic-eating “super” enzymes that can break down the human-made material’s molecular structure faster to aid recycling efforts. In another research effort published in 2019, entomologists noted leaf-cutter bees were using plastic waste to construct their nests. The researchers suggested such behavior could be an “ecologically adaptive trait” and a beneficial recycling effort.

Not so fast, says USU evolutionary ecologist Joseph Wilson. Just because bees can use plastic, doesn’t mean they should.

Wilson and undergraduate researcher Sussy Jones, along with colleagues Scott McCleve, a naturalist and retired math teacher in Douglas, Arizona, and USU alum and New Mexico-based independent scientist Olivia Carril ’00, MS’06, jointly authored an observational paper in the Oct. 9, 2020 issue of Science Matters, exploring the nest building behavior of bees in the genus Megachile.

“Leaf-cutter bees are among the most recognizable of solitary bees, because of their habit of cutting circles out of leaves to build their cylindrical nests,” says Wilson, associate professor of biology at USU-Tooele. “We’ve heard reports of these bees using plastic, especially plastic flagging primarily in construction and agriculture, and we decided to investigate.”

The researchers don’t yet know how widespread the use of plastic by leaf-cutter bees is and they also know little about plastic’s effects on the insects.

“Building from plastic could change the dynamics and environment of the bee’s nest cells, because plastic doesn’t breathe like natural materials,” says Wilson, who produced a video about the phenomenon. “In the 1970s, some researcher let leaf-cutter bees nest in plastic straws and found ninety percent of the bees’ offspring died because of fungal growth. The plastic sealed in the moisture and didn’t allow gas exchange.”

To deter bees’ use of flagging, Wilson suggests use of fabric ribbons made from natural fibers.

“These materials are biodegradable and, if used by bees, will likely avoid the harmful moisture-capturing effects of plastic,” he says.

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University of California, Irvine postdoctoral researcher Adriana Adolfi, in collaboration with colleagues at UCI, UC Berkeley and UC San Diego, followed up on the group’s pioneering effort to develop CRISPR-based gene drive systems for making mosquito vectors resistant to transmitting malaria parasites by increasing gene drive effectiveness in female mosquito progeny.

“This work mitigates a big issue with the first gene drive systems, which is the accumulation of drive-resistant mosquitoes that could still transmit malaria parasites,” said UCI vector biologist Anthony James, the Donald Bren Professor of Microbiology & Molecular Genetics and Molecular Biology & Biochemistry, who was a co-primary investigator on the study.

“The second-generation gene drive system described in this paper can be applied to any of the several thousand genes that are essential for insects to survive or reproduce,” said UC San Diego Distinguished Professor Ethan Bier, a co-author of the study and science director at the Tata Institute for Genetics and Society. “While it was developed in fruit flies, this system is readily transportable to a broad selection of insect species that serve as vectors for devastating disorders such as Chagas disease, sleeping disease, leishmaniasis and arboviral diseases.”

They describe a highly efficient second-generation version of the team’s original gene drive, developed for the Indo-Pakistani malaria vector mosquito Anopheles stephensi. The 2015 work, published in Proceedings of the National Academy of Sciences, was the first demonstration of a CRISPR-based gene drive in mosquitoes.

In that first study, the gene drive was transmitted to about 99 percent of progeny when the parent in which the gene drive was inserted was a male but only 60 to 70 percent of offspring when the parent in which the gene drive was inserted was a female. A significant number of drive-resistant chromosomes are generated in females; this, in principle, could allow those females to continue to transmit parasites.

Adolfi, lead author of the new study, and collaborators solved the failure to drive efficiently through females by equipping the gene drive with a functional copy of the target gene into which the drive is inserted. Normal function of this target gene is required in this mosquito species for female survival and fertility after she feeds on blood, and its functionality is usually disrupted when the drive system is inserted into the gene.

The resulting female mosquitoes showed strong and consistent drive in a population cage study and negligible production of drive-resistant chromosomes. This strategy of inserting a gene drive into a gene essential for viability or fertility and at the same time including a functional gene that rescues the loss of viability or fertility provides a general solution to drive resistance through females. Also, as with a catalytic converter removing combustion pollution from automobiles, the new system efficiently eliminates genetic errors made in the drive process.

This gene drive system — in combination with genes for blocking parasite transmission — can now be used to design field-ready strains of mosquitoes. Thorough testing is required to demonstrate safety and efficacy before advancing to field testing.

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