Now, researchers from the Department of Energy’s Joint BioEnergy Institute (JBEI), Berkeley Lab, and The Novo Nordisk Foundation Center for Biosustainability at Technical University of Denmark (DTU Biosustain) have found a way to engineer the fatty membranes of cells. The researchers boosted the cells’ ability to produce high amounts of fluid fats, so-called unsaturated lipids. This increased the membrane respiration as well as the cell’s growth rate.

This knowledge could be an advantage when engineering the cellular workhorses E. coli or baker’s yeast to produce biofuels, biochemicals or biopharmaceuticals. Therefore, this method could become very important in industries working with cell factories.

The research has now been published in Science.

The researchers showed how to manipulate the lipid composition of E. coli and baker’s yeast. The next step is to show that the method works for mammalian cells as well.

“The applications for future work aren’t industrial, but rather related to health. Several diseases, such as type 2 diabetes, lead to more rigid membranes and also feature impaired mitochondria function,” says first-author, Postdoc Itay Budin from JBEI.

Mitochondria are the cell’s power plants. Cells with impaired mitochondrial function work slowly compared to normal cells. Making the cells’ membrane more fluid could normalize mitochondrial function.

“We are excited about this work — it shows that synthetic biology and metabolic engineering can be applied to gain basic insights in fundamental biological processes. This basic knowledge is very important in order to develop new treatments for diseases that we basically don’t understand the mechanisms behind,” says co-author, Professor at JBEI and Scientific Director at DTU Biosustain Jay Keasling.

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The new research demonstrates how the low-cost hybrid organic-inorganic radiative cooling metamaterial, which debuted in 2017, can be scaled into a roughly 140-square-foot array — small enough to fit on most rooftops — and act as a kind of natural air conditioner with almost no consumption of electricity.

“You could place these panels on the roof of a single-family home and satisfy its cooling requirements,” said Dongliang Zhao, lead author of the study and a postdoctoral researcher in CU Boulder’s Department of Mechanical Engineering.

The findings are described today in the journal Joule and take advantage of natural radiative cooling principles.

“As Earth’s temperature warms due to the absorbed heat from the sunlight during the day, it continuously emits infrared light to the cold universe all the time,” said Professor Ronggui Yang of Mechanical Engineering and lead author of the study. “During the night, Earth cools down due to the emission without the sunshine.”

The researchers’ film-like material reflects incoming almost all sunlight while still allowing an object’s stored heat to escape as much as possible, keeping it cooler than ambient air even in the midday sun.

“The material, which we can now produce at low cost using the current roll-to-roll manufacturing techniques, offers significant advantages.” said Associate Professor Xiaobo Yin of Mechanical Engineering and CU Boulder’s Materials Science and Engineering Program.

“We can now apply these materials on building roof tops, and even build large-scale water cooling systems like this one with significant advantages over the conventional air conditioning systems, which require high amounts of electricity to function,” said Associate Professor Gang Tan of the University of Wyoming’s Department of Civil and Architectural Engineering.

The researchers tested their system outdoors in a variety of weather conditions, including wind, precipitation and humidity. In experiments conducted in August and September 2017, their proprietary RadiCold module kept a container of water covered by the metamaterial 20 degrees Fahrenheit cooler than the ambient air between 12:30 p.m. and 3 p.m., the most intense summer sunlight of the day.

The researchers also introduced an element of dynamic scheduling to their technology, anticipating that structures such as offices may have limited or no cooling demand at night. In a building-integrated system, however, a cold storage unit could be added to capture the cold through heat transfer fluid such as water in this system and allow it to be retrieved during the subsequent day to reduce the cooling strain during peak demand periods.

“We have built a module that performs in real-world, practical situations,” said Yang. “We have moved quite far and fast from a materials level to a system level.”

The RadiCold module could become a viable solution for supplemental cooling for single-family homes, businesses, power plants, municipal utilities and data center facilities among other potential applications, Yang said.

Additional co-authors of the study include CU Boulder graduate students Ablimit Aili and Yao Zhai as well as senior undergraduate students Jiatao Lu and Dillon Kidd of Mechanical Engineering. The U.S. Department of Energy’s Advanced Research Projects Agency — Energy (ARPA-E) provided funding for the research. The technology has been licensed to Radi-Cool Inc.

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Materials provided by University of Colorado at Boulder. Original written by Trent Knoss. Note: Content may be edited for style and length.

The study, which appears in the latest issue of Global Ecology and Conservation, represents the latest information from the first and longest running effort to understand the impact of an increasing human footprint on American black bears at the wildland-urban interface.

The authors looked at expanding bear populations in the Lake Tahoe Basin and Western Great Basin Desert in Nevada, examining 382 bear deaths between 1997 and 2013. They found that the largest causes of mortality were vehicle collisions (160) and management removal of bears (132) due to animals breaking into people’s homes and/or causing property damage, or other threats to human safety.

The authors say that by understanding the causes and consequences of mortality on bears using long-term data, wildlife managers will be able to reduce bear deaths in urban interface areas where bears could otherwise be killed more frequently.

Said the study’s co-author Jon Beckmann, Science Director of WCS’s Rocky Mountain West Program: “Ultimately the goal of conservation is to have more individuals of species like bears and other carnivores on landscapes like we have accomplished in the Great Basin, but we then have to understand how to limit their mortality that results from conflicts with humans.”

Lead author Rae Wynn-Grant from the Museum’s Center for Biodiversity and Conservation suggests “This approach to understanding local drivers of bear mortality can be replicated in other areas where human influence varies across the landscape. We were surprised to find subtle indicators of human activity were important drivers of bear mortality risk, an important finding for wildlife recovery efforts.”

WCS and Nevada Department of Wildlife (NDOW) currently use this information to try and reduce mortality of bears in areas where bears already occur, and to predict hot-spots of human-bear conflict as they currently recolonize their historical range in the state of Nevada. In the Great Basin, bears are returning after an absence of 80-plus years due to recovering habitats and WCS/NDOW conservation efforts such as the Bear Aware Campaign, changing regulations, and policies prohibiting the feeding of wildlife along with ordinances requiring bear-proof dumpsters in many regions of western Nevada. These efforts have led to the bear population expanding in number and geography over the past several years, resulting in bears showing up in areas of central and eastern Nevada.

The authors say that these conservation successes can be a model for other places, including in New York and New Jersey, and areas throughout the U.S. that are dealing with increasing human-bear conflicts at the wildland-urban interface. In addition, the authors say there are lessons for other regions of the globe where large carnivores occur in these wildland-urban interface areas such as lions at the wildland-urban interface of Nairobi, Kenya.

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The olfactory system depends on a complex web of neural connections to detect odors. Olfactory sensory neurons in the nose pass information through their axons to the brain’s olfactory bulb for further processing. Neurons with the same receptor reach out, or project their axons, and connect to the same spot in the brain, called a glomerulus. This convergence forms an olfactory map, and it acts as a kind of code book for the scents we encounter. Glitches in the map’s wiring affect how scents are perceived.

Previously, researchers thought that since olfactory neurons regenerate and replace themselves throughout the life of an animal, they kept the ability to re-establish correct connections. Yu and his team found that wasn’t the case. They used a number of transgenic mouse lines to demonstrate that the first week after birth is a critical window of time to fix problems. If mis-targeting is not corrected during this period, cells still regenerate, but many get locked onto the wrong tracks.

In their follow-up report published online October 25, 2018, in Neuron, the researchers detail the unexpected discovery of a group of olfactory sensory neurons, or navigator neurons, that play an essential role in establishing the olfactory map and correcting faulty connections.

“The results indicate that the map of neural connectivity is set early in life by a group of neurons that only exist during the critical period. Neurons generated at an adult stage do not have this capacity,” says first author Yunming Wu, Ph.D. At the time the research was conducted, Wu was a predoctoral researcher with Open University.

The discovery of navigator neurons is the culmination of five years of research conducted in the Yu lab, aimed at distinguishing early-born neurons from later-born neurons. Because navigator neurons look identical and function the same as neurons born later, it took a variety of creative approaches to finally pinpoint them.

The researchers used a combination of approaches and technologies to identify the neurons. Chronogenetic tracking, a method developed in the lab, allowed them to trace a neuron’s lifespan using genetic labeling across a mouse’s entire life. They constructed an adenovirus to carry genes into the neurons so they could clearly label individual axons emanating from the neurons. By combining virus labeling and CLARITY, a technique that makes samples of mouse brain tissue transparent, they obtained entire trajectories of axon projection into the olfactory bulb. They also used single-cell transcriptome analysis to characterize the molecular identity of the cells and changes of gene expression during development. Used together, these methods demonstrated that navigator neurons are distinct from other olfactory sensory neurons.

The researchers found that the neurons undergo a phase of exuberant axon growth and have a shortened lifespan, as well as distinct molecular signatures. By extending the lifespan of navigator neurons, they prolonged their period of exuberant growth and stopped the axons from converging. They also found that while all of the olfactory sensory nerves were able to regenerate, only the navigators had the ability to establish a convergent map. Navigator neurons also have very different trajectories when they’re projecting during early development — roaming around instead of going straight to the glomeruli. This behavior may help them correct improper connections, because they are able to find new connections by sampling a much larger area.

Learning more about the mechanisms driving navigator neurons, and their role in establishing olfactory map wiring, could hold promise for regenerating and repairing olfactory neurons and neurons in other types of neural systems, such as those involved in spinal cord injury. Finding out how to make later-born neurons that have lost their ability to regenerate and connect correctly behave like navigator neurons might be the key.

“We know that when there’s trauma-related anosmia, the sense of smell is lost because of the severing of connection from sensory neurons to the olfactory bulb. When the axons get cut, even when they regenerate, if they cannot re-form the connections properly, you would still lose the sense of smell or have an altered perception of smell,” Yu says. “If we can understand this process involved in early development — if we can reopen the critical period- we may be able to let regenerating axons find the right target when they are projecting back. This study is a step towards that goal.”

In addition to Yu and Wu, other study contributors from the Stowers Institute include Limei Ma, Ph.D., Kyle Duyck, Carter Long, Andrea Moran, Hayley Scheerer, Jillian Blanck, Allison Peak, and Andrew Box. This research was assisted by Stowers scientific support teams including Computational Biology, Cytometry, Laboratory Animal Services, Microscopy, and Molecular Biology.

The study was funded by the Stowers Institute for Medical Research and the National Institute on Deafness and Other Communication Disorders of the National Institutes of Health (award R01DC016696). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Lay Summary of Findings

A newly discovered group of “navigator neurons” may hold the key to understanding the neural circuitry behind our sense of smell. The study builds on a breakthrough 2014 report from the laboratory of Stowers Investigator Ron Yu, Ph.D., that showed a critical period in olfactory wiring. Glitches in the wiring affect how scents are perceived. Yu and his colleagues found that in mice, there’s a brief window to fix problems — about a week after mice are born.

In their follow-up report published online October 25, 2018, in Neuron, the researchers detail the surprise discovery of a group of olfactory sensory neurons, or “navigator” neurons, that play an essential role in establishing the olfactory map, a kind of code book for the scents we encounter. The navigator neurons also correct faulty wiring that can impair the sense of smell. Because navigator neurons look identical and function the same as other neurons, the Stowers researchers creatively employed a variety of approaches and technologies, some they developed themselves, to finally pinpoint them. Learning more about navigator neurons could hold promise for regenerating and repairing olfactory neurons and neurons in other types of neural systems, such as those involved in spinal cord injury.

“Xylem is an important resource for land plant biomass. Modifications of xylem cell differentiation are important for strategies to improve plant biomass resources,” believes Demura.

The secondary cell wall is composed of three types of polymers, cellulose, hemicellulose, and lignin. In a new study that can be read in Plant Cell, Demura’s laboratory found that these three polymers in xylem cell mutants contribute to secondary cell wall formation independently of each other, challenging the contemporary model of plant growth.

Interaction between cellulose and hemicellulose is critical for giving cell walls their strength and elasticity to push water upward. Interaction with lignin adds the hydrophobicity that gives an electrical charge to the push. Studies in the early 1980s had convinced scientists that the formation of the secondary cell wall occurs in consecutive events, beginning with the synthesis of cellulose at the cell surface, followed by the deposition of hemicellulose that bonds to the cellulose, and finally the migration and polymerization of lignin.

These interactions result in the three polymers taking an obvious spatial pattern in xylem cells. However, xylem cells in a mutation of Arabidopsis thaliana, a small plant commonly used by scientists to study plant growth, made by the Demura lab, showed disrupted cellulose synthesis without disruption of the spatial patterning of hemicellulose or lignin.

“We made a mutation in the cellulose synthase gene CESA7. This mutation prevented the formation of cellulose. Despite the lack of patterned cellulose deposition, we saw patterned deposition of hemicellulose and lignin,” explains Dr. Misato Ohtani, who contributed to the project.

Additional study revealed that the sustained patterning could be attributed to microtubules, molecules seen in just about all life, including humans, and is responsible for transporting materials within cells.

“We were able to disrupt the hemicellulose and lignin patterning when we disrupted the microtubules with a drug. This suggests that during secondary cell wall formation, the hemicellulose and lignin are regulated by microtubules and not cellulose,” continued Ohtani.

Considering the increasing efforts to bioengineer plants that can produce resources at higher efficiencies or withstand extreme changes in climate, Demura notes that elucidating the mechanisms of how fundamental plant structures like the secondary cell wall develop will help scientists achieve these goals.

“Identifying the independence of cellulose, hemicellulose and xylan suggests we can modify one without modifying the other in plants,” he says.

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