Despite setbacks from the pandemic, renewable energy deployment is increasing. The Inflation Reduction Act extends renewable energy tax credits and helps remove barriers for low-income households to use clean energy. Although supply chain shortages have created hurdles across the energy industry, 2023 has the potential to be a promising year for the transition to clean energy. Let’s examine the forces at play for renewables in 2023.

High Fossil Fuel Costs Make Renewable Energy More Cost-Effective

The price of oil, natural gas, and coal has been rising, and quite erratic, partly due to the Russian invasion of Ukraine. A natural gas shortage has temporarily spiked interest in coal, causing prices to soar last March and then rise and dip repeatedly since. Although some markets are using more coal during natural gas shortages, a return to coal power is counterproductive for mitigating the climate crisis.

An increase in natural gas and coal prices impacts our electricity rates because so much electricity in the U.S. is produced from fossil fuels. Last year, 22% of electricity was generated from coal and 38% from natural gas. As a result of higher gas and coal prices, the average cost of electricity has increased by around 8% from 2021 to 2022, according to estimates from the Energy Information Administration. However, the transition to renewable energy requires investments and a few years to bring utility-scale projects online.

“Russia’s invasion of Ukraine is prompting a wholesale reorientation of global energy trade, leaving Russia with a much-diminished position,” according to a report by the International Energy Agency (IEA). To help shield consumers from rising prices, many governments are “accelerating the flow of new renewables projects.”

Although wind and solar energy have become cost-competitive with other energy sources?, the increase in coal and natural gas costs makes solar and wind power? more cost-effective than fossil fuels in most cases. According to BloombergNEF, “New onshore wind now costs about $46 per megawatt-hour, while large-scale solar plants cost $45 per megawatt-hour. In comparison, new coal-fired plants cost $74 per MWh, while gas plants are $81 per MWh.”

Also, as the cost of electricity increases, installing a rooftop solar energy system becomes more cost-effective, and solar panels pay for themselves in savings more quickly.

Energy Storage Technology and Deployment Is Advancing

Most renewable power sources are intermittent because the sun doesn’t always shine, and the wind doesn’t always blow. Thus, energy storage is critical for renewables to become more widespread. The price of energy storage is still relatively high, but it is gradually decreasing. Likewise, promising energy storage technologies are advancing, such as solid-state batteries.

These batteries could eventually overtake lithium-ion (Li-ion) batteries, using a solid electrolyte instead of a liquid or gel found in current Li-ion batteries. They have a higher energy density, so they are more compact. Also, they don’t require the cooling and control components that Li-ion batteries do, so they have a smaller footprint and lower weight. This feature is essential for electric vehicles but also helpful for stationary battery energy storage systems.

“Solar PV homeowners will love our solid-state energy storage systems because they offer superior performance and are non-explosive, non-flammable, non-toxic, and 100% recyclable,” said Damir Perge, CEO and co-founder of Ampricity. The company plans to start manufacturing solid-state batteries for residential and commercial use in its U.S. factory by 2024.

Researchers from MIT recently announced that they created an aluminum-sulfur battery, which they say can be deployed for a fraction of the price of Li-ion batteries, are safer, and are recyclable. Although they aren’t ready for widescale production, this development shows that battery technology is advancing.

Innovative Approaches to Solar Energy Becoming More Common

An increasing number of states have policies that encourage community solar farms, which allow subscribers to enjoy many of the benefits of solar energy without installing solar panels on their properties. This makes solar energy more feasible for renters, low to moderate-income households, multifamily unit dwellers, and people with shaded roofs.

Some of the best states for community solar are Colorado, Illinois, Maine, Maryland, Massachusetts, Minnesota, New Jersey, New York, and Rhode Island. However, Hawaii, New Mexico, and Virginia have recently passed laws supporting community solar, so these markets are likely to heat up.

Increasingly, solar developers are incorporating innovative practices at solar farms, such as planting native wildflowers to promote pollinator habitat or grazing sheep instead of using gas-powered mowers. Some solar developers are even experimenting with planting crops at solar farms, in a practice known as agrivoltaics. In California, solar developers are installing solar panels on some irrigation canals to prevent evaporation and efficiently use space.

However, as solar and wind farms become more prevalent, some communities oppose them for various reasons. Adding dual-use features such as food production can help overcome concerns while providing additional benefits.

The state of the global energy industry will be in a state of flux in 2023 due to fluctuating supplies and shifting demand. However, as technology matures, the capabilities of renewable energy technologies and energy storage are also advancing.

“Large uncertainties exist for the current forest assessments internationally. By mapping the carbon stock of all individual trees, accuracy is greatly improved. Further, the way different countries make their inventories is not consistent due to different contexts, goals, and available datasets. We hope that this method will establish itself as a standard, thereby enabling better comparisons between countries,” says PhD Researcher Maurice Mugabowindekwe, Department of Geosciences and Natural Resources Management (IGN), University of Copenhagen. He is first author on the scientific article presenting the new method. The article has been accepted for publication by Nature Climate Change, one of the most prominent journals for the field.

Maurice Mugabowindekwe being Rwandan himself is helpful during the work, but the choice of Rwanda for development of the method was scientifically based, he emphasizes:

“The country has a rich landscape variation including savannas, woodlands, sub-humid and humid forests, shrubland, agro-ecosystem mosaics, and urban tree ecosystems which are representative of most tropical countries. We wanted to prove the method for all these landscape types. Moreover, Rwanda is a signatory to several international agreements on forest preservation and climate change mitigation. For instance, Rwanda has pledged to restore about 80 % of its surface area by 2030 under the Bonn Challenge. So, it is highly relevant to have a reliable method for monitoring tree carbon.”

First method for mapping individual trees

Preservation of natural forests and planting of new trees are recognized as vital routes to limiting climate change. However, large uncertainties regarding the carbon content of the trees have made it hard to assess the efficiency of concrete initiatives. The University of Copenhagen researchers have overcome this problem.

The new method benefits from databases which give the relationship between the extent of the crown and the total carbon content of an individual tree.

“Mapping individual trees and calculating their carbon stocks has traditionally been done in forestry, albeit at a much smaller scale. Basically, what we do equals scaling up these approaches from a very local to a national level,” says Researcher Ankit Kariryaa, working 50:50 at IGN and at the Department of Computer Sciences (DIKU). Scientists from these two University of Copenhagen departments have developed the method with IGN as lead, in collaboration with other international scientists.

The new method will support Rwanda in verifying fulfilment of commitments under schemes such as the global forestry climate change mitigation scheme REDD+ or the African Forest Landscape Restoration Initiative, AFR 100.

Many trees are found outside forests

Manually mapping the trees of an entire country would be a huge endeavor and excessively costly. Thus, the new method constitutes a breakthrough since no other method would realistically be able to provide the same information at the level of individual trees.

“It is important to take a holistic approach and also include trees which are outside forests,” says Ankit Kariryaa, noting that 72 % of the mapped trees were in farmlands and savannas, and 17 % in plantations.

At the same time, the relatively small proportion of trees which are found in natural forests — 11 % of the total tree count — comprise about 51 % of the national carbon stock of Rwanda. This is possible mainly because natural forests have a very high carbon content per tree volume, thanks to the very low human disturbance secured through national legislation.

“This suggests that conservation, regeneration, and sustainable management of natural forests is more effective at mitigating climate change than plantation,” Maurice Mugabowindekwe comments.

Rainforest appears to be “a huge green blanket”

It is paramount that the computer can distinguish the individual trees. This is because the relationship between the extent of the crown and the total carbon content of a tree is very different depending on the size of a tree. One very large tree will have a much higher carbon content than a group of trees with the same joint crown extent. So, if the group was mistaken for one tree, the carbon content would be significantly overestimated. A deep neural network is used for detecting the individual trees.

“Especially for the rainforest, it is highly challenging to determine how many different trees are present in an image. At first glance, the forest just appears to be one huge green blanket. But by using methods from Machine Learning and Computer Vision, our system can also be applied to identify the individual trees in overstory of dense forests,” explains Christian Igel, Professor of Machine Learning at DIKU.

Training the computer on verified samples is at the core of Machine Learning. In the Rwandan study, the computer was trained on a set of some 97,500 manually delineated tree crowns representing the full range of biogeographical conditions across the country.

The study used publicly available aerial and satellite images of Rwanda at 0.25 x 0.25 m resolution. These images were collected in June-August 2008 and 2009 and were provided by the Rwanda Land Management and Use Authority and the University of Rwanda. More than 350 million trees were mapped.

Applications beyond Rwanda

Nine researchers from University of Copenhagen visited Rwanda in July 2022 with a dual purpose of field work and presenting results from the first nation-wide mapping to the Rwandan authorities and other stakeholders in the country’s forestry sector.

“The presentation was well received,” reports Maurice Mugabowindekwe. He was immediately tasked by the Rwandan authorities with an updated mapping based on newer aerial images acquired in 2019. This work is now ongoing.

Further, the method has already been tested for a handful of countries besides Rwanda. These include Tanzania, Burundi, Uganda, and Kenya.

“We hope countrywide high-resolution satellite imagery can also be acquired for these and more countries, to enable the application of the same approach. Also, we advocate the inclusion of funding for regular high-resolution imagery along with localized field inventory databases in development packages to enable similar works across the globe,” says Maurice Mugabowindekwe, adding:

“The method has yielded good results when applied directly to a new country or region. If the model is further trained on a local set of samples, the accuracy becomes even higher. In my opinion, inventory of the available woody plants, their location, size, and carbon stock, is the first step towards monitoring the impact of landscape restoration efforts as well as conservation. If you are not able to create an accurate and reliable inventory, there is a risk of lacking a framework to track the impact of landscape restoration. This could make the conservation and sustainable management of both forests and other tree-dominated landscapes impossible. Therefore, this is science which is likely to have an impact.”

To better understand which species are most vulnerable and identify the most cost-effective actions, researchers combined expert assessments with scientific data to evaluate threats and conservation strategies for Antarctica. They asked 29 experts to define possible management strategies, estimate their cost and feasibility, and assess the potential benefit to different species between now and 2100.

Climate change was identified as the most serious threat to Antarctic biodiversity and influencing global policy to limit warming was the most beneficial conservation strategy. Under current management strategies and more than 2 degrees Celsius of warming, 65% of land plants and animals will decline by 2100. Emperor penguins (Aptenodytes forsteri) were identified as the most vulnerable, followed by other sea birds and soil nematode worms. However, regional management strategies could benefit up to 74% of plants and animals at an estimated cost of 1.92 billion US dollars over the next 83 years, equating to 0.004% of global GDP in 2019. The regional management strategies identified as offering the greatest return on investment were minimizing the impacts of human activities, improving the planning and management of new infrastructure projects, and improving transport management.

As Antarctica faces increasing pressure from climate change and human activities, a combination of regional and global conservation efforts is needed to preserve Antarctic biodiversity and ecosystem services for future generations, the authors say.

Lee adds, “What this work shows is that climate change is the greatest threat to Antarctic species and what we need is global mitigation efforts to save them. This will not only help to secure their future, but also our own.”

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“There are more than 150 species of known glassfrogs in the world, and yet we’re really just starting to learn about some of the really incredible ways they interact with their environment,” said co-lead author Jesse Delia, a Gerstner postdoctoral fellow in the Museum’s Department of Herpetology.

Glassfrogs, which live in the American tropics, are nocturnal amphibians that spend their days sleeping upside down on translucent leaves that match the color of their backs — a common camouflage tactic. Their tummies, however, show something surprising: translucent skin and muscle that allows their bones and organs to be visible, giving the glassfrog its common name. Recent research has proposed that this adaptation masks the frogs’ outlines on their leafy perches, making them harder for predators to spot.

Transparency is a common form of camouflage among animals that live in water, but it’s rare on land. In vertebrates, attaining transparency is difficult because their circulatory system is full of red blood cells that interact with light. Studies have shown that ice fish and larval eels achieve transparency by not producing hemoglobin and red blood cells. But glassfrogs use an alternative strategy, according to the findings of the new study.

“Glassfrogs overcome this challenge by essentially hiding red blood cells from view,” said Carlos Taboada, the study’s co-lead author from Duke University. “They almost pause their respiratory system during the day, even at high temperatures.”

At Duke, the researchers used a technique called photoacoustic imaging, which uses light to induce sound-wave propagation from red blood cells. This allows researchers to map the location of the cells within sleeping frogs without restraint, contrast agents, sacrifice, or surgical manipulation — particularly important to this study because glassfrog transparency is disrupted by activity, stress, anesthesia, and death.

The researchers focused on one particular species of glassfrog, Hyalinobatrachium fleischmanni. They found that resting glassfrogs increase transparency two- to threefold by removing nearly 90 percent of their red blood cells from circulation and packing them within their liver, which contains reflective guanine crystals. Whenever the frogs need to become active again, they bring the red blood cells back into the blood, which gives the frogs the ability to move around — at which point, light absorption from these cells breaks transparency.

In most vertebrates, aggregating red blood cells can lead to potentially dangerous blood clots in veins and arteries. But glassfrogs don’t experience clotting, which raises a set of significant questions for biological and medical researchers.

“This is the first of a series of studies documenting the physiology of vertebrate transparency, and it will hopefully stimulate biomedical work to translate these frogs’ extreme physiology into novel targets for human health and medicine,” Delia said.

Other authors on the study include Maomao Chen, Chenshuo Ma, Xiaorui Peng, Xiaoyi Zhu, Tri Vu, Junjie Yao, and So?nke Johnsen from Duke University; Laiming Jiang and Qifa Zhou, from the University of Southern California, Los Angeles; and Lauren O’Connell, from Stanford University.

This study was supported in part by the National Geographic Society, grant # NGS-65348R-19; the Human Frontier Science Program postdoctoral fellowship # LT 000660/2018-L; the Gerstner Scholars Fellowship provided by the Gerstner Family Foundation and the Richard Gilder Graduate School at the American Museum of Natural History; start-up funds from Stanford University; start-up funds from Duke University; the National Institutes of Health, grant #s R01 EB028143, R01 NS111039, RF1 NS115581 BRAIN Initiative; a Duke Institute of Brain Science Incubator award; the American Heart Association Collaborative Sciences award 18CSA34080277; and a Chan Zuckerberg Initiative grant 2020- 226178.

“In short, we found biology textbooks are failing to share adequate information about climate change, which is a generation-defining topic in the life sciences,” says Jennifer Landin, corresponding author of the study and an associate professor of biological sciences at NC State. “These books are the baseline texts for helping students understand the science of life on Earth, yet they are providing very little information about a phenomenon that is having a profound impact on habitats, ecosystems, agriculture — almost every aspect of life on Earth.”

For the study, researchers analyzed coverage of climate change in 57 college biology textbooks published between 1970 and 2019. The researchers found that climate coverage has varied substantially over those five decades.

Prior to 1990, textbooks had a median of fewer than 10 sentences addressing climate change. In the 1990s, the median length of climate content was 30 sentences. The median length of climate content rose to 52 sentences in the 2000s, which is not surprising given the amount of emerging research into climate change and its impacts. However, the researchers found that the amount of climate coverage in textbooks actually declined in the 2010s — dropping to a median of 45 sentences.

In addition to length, the nature of the content has also changed substantially over time. For example, sentences dedicated to actionable solutions to climate change peaked in the 1990s at more than 15% of the climate content. However, in more recent decades, actionable solutions make up only about 3% of the climate content.

“One of the most troubling findings was that textbooks are devoting substantially less space to addressing climate solutions now than they did in the 1990s — even as they focus more on the effects of climate change,” Landin says. “That suggests to students that nothing can be done, which is both wildly misleading and contributes to a sense of fatalism regarding climate change.”

In addition, the position of climate change sections keeps moving further back in the books, from the last 15% of the overall text in the 1970s to the last 2.5% of the text in the 2010s.

“This is important because most instructors present textbook content in order, which means topics at the end of the book are often skipped,” Landin says.

“However, it’s not all bad news,” Landin adds. “Textbooks in the 2000s and 2010s began including a wider variety of climate-relevant information, such as how climate is affecting species distributions, which can help students understand the various impacts of climate change.

“However, we are hoping that this study will serve as a wake-up call for publishers and instructors. We need to do a much better job of incorporating climate change into our courses if we want to prepare students to understand the role that climate change is playing in shaping life on Earth and how we study it.”

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Combining data from the long-term Hawai’i Ocean Time-series program with new climate model simulations conducted on one of South Korea’s fastest supercomputers, the scientists revealed that a mechanism, known as nutrient uptake plasticity, allows marine algae to adapt and cope with nutrient-poor ocean conditions expected to occur over the next decades in response to global warming of the upper ocean.

Phytoplankton are tiny algae which drift at the ocean’s surface and form the basis of the marine food web. While photosynthesizing, these algae absorb nutrients (e.g., phosphate, nitrate), take up dissolved carbon dioxide and release oxygen, which makes up for about 50% of the oxygen that we breathe. Knowing how marine algae will respond to global warming and to associated decline of nutrients in upper ocean waters is therefore crucial for understanding the long-term habitability of our planet.

How the annual phytoplankton production rate will change globally over the next 80 years remains highly uncertain. The latest report of the Intergovernmental Panel on Climate Change (IPCC) states an uncertainty of -20% to +20%, which implies an uncertainty as to whether phytoplankton will increase or decrease in future.

Global warming affects the upper layers of the ocean more than the deeper layers. Warmer water is lighter and hence the upper ocean will become more stratified in future, which reduces mixing of nutrients from the subsurface into the sun-lit layer, where phytoplankton reside. Earlier studies suggested that the expected future depletion of nutrients near the surface would lead to a substantial reduction of ocean’s phytoplankton production with widespread and potentially catastrophic effects on both marine ecosystems and climate.

But according to a new study in Science Advances, this may not happen. New analyses of the upper ocean phytoplankton data from Hawai’i Ocean Time-series program shows that productivity can be sustained, even in very nutrient-depleted conditions. “Under such conditions individual phytoplankton cells can substitute phosphorus with sulfur. On a community level, one might see further shifts towards taxa that require less phosphorus,” says David Karl, a coauthor of the study, Professor in Oceanography at the University of Hawai’i and co-founder of the Hawai’i Ocean Time-series Study program, to illustrate the concept of phytoplankton plasticity. Further supporting evidence for plasticity comes from the fact that in subtropical regions, where nutrient concentrations in the surface waters are low, algae take up less phosphorus per amount of carbon stored in their cells, as compared to the global mean.

To study how this unique metabolic “hack” will impact global ocean productivity over the next few decades, the team ran a series of climate model simulations with the Community Earth System model (version 2, CESM2) on their supercomputer Aleph. By turning off the phytoplankton plasticity in their model, the authors were able to qualitatively reproduce previous model results of a decline in global productivity by about 8%. However, when turning on the plasticity parameter in their model, in a way that captures the observations near Hawai’i for the past 3 decades, the computer simulation reveals an increase in global productivity of up to 5% until the end of this century. “Regionally, however, these future productivity differences can be much higher, reaching up to 200% in subtropical regions,” says Dr. Eun Young Kwon, first author of the study and a researcher at the IBS Center for Climate Physics at Pusan National University, South Korea. With this extra productivity boost, the ocean can also take up more carbon dioxide from the atmosphere and eventually sequester it below the ocean’s surface.

Inspired by the results of their sensitivity computer model simulations, the authors then looked at 10 other climate models, whose data were used in the recent 6^th Assessment Report of the IPCC. The results confirmed the author’s initial conclusions. “Models without plasticity tend to project overall declining primary production for the 21^st century, whereas those that account for the capability of phytoplankton to adapt to low nutrient conditions show on average increasing global productivity” says Dr. M.G. Sreeush, co-corresponding author of the study and a postdoctoral fellow at the IBS Center for Climate Physics.

“Even though our study demonstrates the importance of biological buffering of global-scale ecological changes, this does not imply that phytoplankton are immune to human induced climate change. For instance, worsening ocean acidification will reduce the calcification rates of certain types of phytoplankton, which can lead to large-scale shifts in ecosystems.” warns Dr. Eun Young Kwon. These factors are neither well understood nor represented yet in climate models.

“Future Earth system models need to use improved observationally-based representations of how phytoplankton respond to multiple stressors, including warming and ocean acidification. This is necessary to predict the future of marine life on our planet” says Prof. Axel Timmermann, a coauthor of this study and director of the IBS Center for Climate Physics.

Until now, when people talked about electric vehicles, they were talking about automobiles. But as cars reach a tipping point, and electric options for SUVs, pickups, and even school buses begin to proliferate, innovators are starting to look to the skies. Electric airplanes may be the next big thing in sustainable transportation.

Electric Vehicles

Twenty years ago, many people argued that electric vehicles would never take off. Many people thought that the drawbacks of EVs – short range, high cost, limited charging stations – would keep mainstream consumers from making the switch. Today, there is plenty of consumer demand, and there are high-performance options to meet it. From sports cars to pickup trucks, EV drivers are no longer limited by a hippie aesthetic.

How much your EV benefits the environment compared to a gas-powered vehicle depends in large part on the source of your electricity. Consumers are waking up to this reality and showing increased interest in charging their EVs with solar power – you can even buy a combined solar panel/EV charging system from IKEA now. Corporations are switching to electric fleets, and vehicle-to-grid technology allows communities to use publicly owned fleets as a climate resilience strategy to store electricity for use during natural disasters.

Impacts of Air Travel

Air travel contributes about 3% of the global greenhouse gas emissions that cause climate change. That’s only a small part of the emissions from the transportation sector as a whole, which is still dominated by road transport, especially in the U.S. But Americans contribute more than their fair share of aviation emissions, too; flights from airports in the United States were responsible for almost one-quarter of global passenger flight-related carbon dioxide emissions.

On average, a flight produces more than 53 pounds of carbon dioxide per mile. A round trip transatlantic flight generates about 986 kilograms of CO2 per passenger. That is more than a year’s worth of emissions from the average person in 56 countries, and enough to melt 32 square feet of Arctic summer sea ice. Because airplanes directly release emissions at high altitudes, their impact may be even more pronounced.

You can try to make your flights more sustainable through waste-reduction and purchasing carbon offsets. But since flying is often a discretionary activity, some people are rethinking the decision to fly at all, choosing to just stay home, take the train, or explore slow travel.

Electric Airplanes

Not everyone can or will choose to stay on the ground. So it’s important to reduce the emissions from airplanes. Although changes have not been adopted across the industry, there has been some progress. Some airlines have worked to develop more efficient engines and biofuels. In 2016, 191 nations signed an agreement to reduce aviation-related carbon dioxide emissions 50% by 2050. Considering the success of EVs, electric aircraft engines are among the most promising options for achieving that goal.

Battery technology is the limiting factor in developing viable electric planes. Batteries are about 30 times heavier than the volume of kerosene jet fuel that could provide the same amount of energy. As with road-based EVs, hybrid technology may be the solution that gets electric flight off the ground. Using a combination of electric batteries and jet fuel helps balance the power to weight ratio. Researchers are working to address the power to weight ratio in other ways, for example, by reducing the weight of the engine itself and of the power converters.

Not Ready for Takeoff

Los Angeles-based Wright Electric is developing commercial jets with 100 and 186 seats. But most of the companies working towards electric flight are starting small. Icelandair is partnering with Heart Aerospace to develop an electric plane for domestic flights. The aircraft will have a range of about 200 kilometers with 30 passengers on electricity alone, or 400 kilometers with a combination of electricity and sustainable jet fuel. With the passenger count reduced to 25, the plane could travel up to 800 kilometers. Although not scheduled for delivery until 2028, the company already received nearly 100 orders from several countries.

While electrified commercial flights are still a few years out, the technology is not completely untested. In August, Icelandair performed a test of the first “passenger flight” of an electric aircraft. The Icelandic president and prime minister were the passengers on the inaugural flight of Pipistrel’s new Velis Electro. It is a fully electric small plane designed for pilot training.

In September, Eviation, a start-up based in Washington state, tested its prototype electric passenger plane. It built the plane to carry nine passengers as proof of concept for a fully electric commercial commuter plane. Powered by more than 21,500 battery cells that make up half the weight of plane’s frame, “Alice” reached 3,500 feet and flew for eight minutes. Although the test was considered a complete success, Eviation admits that the current technology is insufficient for commercial purposes and estimates it will take five years to complete a financially viable commercial electric airplane.

Bacteriophages or “phages” is the terms used for viruses that infect bacteria. The UAB researchers, led by Terje Dokland, Ph.D., in collaboration with Asma Hatoum-Aslan, Ph.D., at the University of Illinois Urbana-Champaign, have described atomic models for all or part of 11 different structural proteins in phage Andhra. The study is published in Science Advances.

Andhra is a member of the picovirus group. Its host range is limited to S. epidermidis. This skin bacterium is mostly benign but also is a leading cause of infections of indwelling medical devices. “Picoviruses are rarely found in phage collections and remain understudied and underused for therapeutic applications,” said Hatoum-Aslan, a phage biologist at the University of Illinois.

With emergence of antibiotic resistance in S. epidermidis and the related pathogen Staphylococcus aureus, researchers have renewed interest in potentially using bacteriophages to treat bacterial infections. Picoviruses always kill the cells they infect, after binding to the bacterial cell wall, enzymatically breaking through that wall, penetrating the cell membrane and injecting viral DNA into the cell. They also have other traits that make them attractive candidates for therapeutic use, including a small genome and an inability to transfer bacterial genes between bacteria.

Knowledge of protein structure in Andhra and understanding of how those structures allow the virus to infect a bacterium will make it possible to produce custom-made phages tailored to a specific purpose, using genetic manipulation.

“The structural basis for host specificity between phages that infect S. aureus and S. epidermidis is still poorly understood,” said Dokland, a professor of microbiology at UAB and director of the UAB Cryo-Electron Microscopy Core. “With the present study, we have gained a better understanding of the structures and functions of the Andhra gene products and the determinants of host specificity, paving the way for a more rational design of custom phages for therapeutic applications. Our findings elucidate critical features for virion assembly, host recognition and penetration.”

Staphylococcal phages typically have a narrow range of bacteria they can infect, depending on the variable polymers of wall teichoic acid on the surface of different bacterial strains. “This narrow host range is a double-edged sword: On one hand, it allows the phages to target only the specific pathogen causing the disease; on the other hand, it means that the phage may need to be tailored to the patient in each specific case,” Dokland said.

The general structure of Andhra is a 20-faced, roundish icosahedral capsid head that contains the viral genome. The capsid is attached to a short tail. The tail is largely responsible for binding to S. epidermidis and enzymatically breaking the cell wall. The viral DNA is injected into the bacterium through the tail. Segments of the tail include the portal from the capsid to the tail, and the stem, appendages, knob and tail tip.

The 11 different proteins that make up each virus particle are found in multiple copies that assemble together. For instance, the capsid is made of 235 copies each of two proteins, and the other nine virion proteins have copy numbers from two to 72. In total, the virion is made up of 645 protein pieces that include two copies of a 12th protein, whose structure was predicted using the protein structure prediction program AlphaFold.

The atomic models described by Dokland, Hatoum-Aslan, and co-first authors N’Toia C. Hawkins, Ph.D., and James L. Kizziah, Ph.D., UAB Department of Microbiology, show the structures for each protein — as described in molecular language like alpha-helix, beta-helix, beta-strand, beta-barrel or beta-prism. The researchers have described how each protein binds to other copies of that same protein type, such as to make up the hexameric and pentameric faces of the capsid, as well as how each protein interacts with adjacent different protein types.

Electron microscopes use a beam of accelerated electrons to illuminate an object, providing much higher resolution than a light microscope. Cryo-electron microscopy adds the element of super-cold temperatures, making it particularly useful for near-atomic structure resolution of larger proteins, membrane proteins or lipid-containing samples like membrane-bound receptors, and complexes of several biomolecules together.

In the past eight years, new electron detectors have created a tremendous jump in resolution for cryo-electron microscopy over normal electron microscopy. Key elements of this so-called “resolution revolution” for cryo-electron microscopy are:

• Flash-freezing aqueous samples in liquid ethane cooled to below -256 degrees F. Instead of ice crystals that disrupt samples and scatter the electron beam, the water freezes to a window-like “vitreous ice.”
• The sample is kept at super-cold temperatures in the microscope, and a low dose of electrons is used to avoid damage to the proteins.
• Extremely fast direct electron detectors are able to count individual atoms at hundreds of frames per second, allowing sample movement to be corrected on the fly.
• Advanced computing merges thousands of images to generate three-dimensional structures at high resolution. Graphics processing units are used to churn through terabytes of data.
• The microscope stage that holds the sample can also be tilted as images are taken, allowing construction of a three-dimensional tomographic image, similar to a CT scan at the hospital.

The analysis of Andhra virion structure by the UAB researchers started with 230,714 particle images. Molecular reconstruction of the capsid, tail, distal tail and tail tip started with 186,542, 159,489, 159,489 and 159,489 images, respectively. Resolution ranged from 3.50 to 4.90 angstroms.