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Small brain, astounding performance

How elephant nose fish switch between electrical, visual sense

Source: University of Bonn


Summary: The elephant nose fish explores objects in its surroundings by using its eyes or its electrical sense -- sometimes both together. Zoologists have now found out how complex the processing of these sensory impressions is. With its tiny brain, the fish achieves performance comparable to that of humans or mammals.
 

Gerhard von der Emde and Sarah Schumacher are from the Institute of Zoology at University of Bonn. Credit: Photo by Barbara Frommann/Uni Bonn

The elephant nose fish explores objects in its surroundings by using its eyes or its electrical sense -- sometimes both together. Zoologists at the University of Bonn and a colleague from Oxford have now found out how complex the processing of these sensory impressions is. With its tiny brain, the fish achieves performance comparable to that of humans or mammals. The advance results have been published online in the Proceedings of the National Academy of Sciences.

The elephant nose fish (Gnathonemus petersii) is widespread in the flowing waters of West Africa and hunts insect larva at dawn and dusk. It is helped by an electrical organ in its tail, which emits electrical impulses. The skin contains numerous sensor organs that perceive objects in the water by means of the changed electrical field. "This is a case of active electrolocation, in principle the same as the active echolocation of bats, which use ultrasound to perceive a three-dimensional image of their environment," says Professor Dr. Gerhard von der Emde at the Institute of Zoology at the University of Bonn. Furthermore, the elephant nose fish can also orient using its eyes.

Professor von der Emde, along with his doctoral candidate Sarah Schumacher and Dr. Theresa Burt de Perera of Oxford University, have now investigated how the unusual fish processes the information from the various sensory channels. Ms. Schumacher summarizes the results: "The animals normally use both senses. If necessary, for example because one of the two senses provides no information or the information of the two senses differs greatly, however, the fish can switch back and forth between their visual and electrical senses." The scientists were surprised by the manner in which the fish use these two senses to get the best perception of their environment: When the animals became familiar with an object in the aquarium, for example with the visual sense, they were also able to recognize it again using the electrical sense, although they had never perceived it electrically before.

Fish give precedence to the most reliable sensory information.

In addition, the fish demonstrated a previously unexpected ability: Their brain gave more weight to the information it thought was more reliable. When the two senses delivered different information in the close range of up to two centimeters, the fish trusted only the electrical information and were then "blind" to the visual stimuli. In contrast, for more distant objects, the animals relied above all on their eyes. They perceived the environment best by using their visual and electrical senses in combination. "A transfer between the different senses was previously known only for certain highly developed mammals, such as monkeys, dolphins, rats, and humans," says Professor von der Emde. An example: In a dark, unfamiliar apartment, people feel their way forward to avoid stumbling. When the light goes on, the obstacles felt are recognized by the eye without any problem. Mammals process such information with their cerebral cortex. The elephant nose fish, however, has just a relatively small brain and no cerebral cortex at all -- but nevertheless switches back and forth between the senses.

Clever experimental setup

The scientists came up with a very clever test setup: The elephant nose fish was in an aquarium. Separated from it were two different chambers, between which the animal could choose. Behind openings to the chambers there were differently shaped objects: a sphere or a cuboid. The fish learned to steer toward one of these objects by being rewarded with insect larvae. Subsequently, it searched for this object again, to obtain the reward again.

When does the fish use a particular sense? In order to answer this question, the researchers repeated the experiments in absolute darkness. Now the fish could rely only on its electrical sense. As shown by images taken with an infrared camera, it was able to recognize the object only at short distances. With the light on the fish was most successful, because it was able to use its eyes and the electrical sense for the different distances. In order to find out when the fish used its eyes alone, the researchers made the objects invisible to the electrical sense. Now, the sphere and cuboid to be discriminated had the same electrical characteristics as the water.

Many repetitions of the individual experiments were necessary in order to apply statistical analyses to reach conclusions about the sensory processing of the elephant nose fish. The scientists worked with a total of ten animals, working more or less in shifts. "The behavior of the different individuals was nearly identical," says Professor von der Emde. For that reason the scientists are certain that this enormous sensory performance is achieved not only by a particularly talented specimen but by all elephant nose fish.

Story Source:
The above post is reprinted from materials provided by University of Bonn.

Journal Reference:
Sarah Schumacher, Theresa Burt de Perera, Johanna Thenert, Gerhard von der Emde. Cross-modal object recognition and dynamic weighting of sensory inputs in a fish. Proceedings of the National Academy of Sciences, 2016; 201603120 DOI: 10.1073/pnas.1603120113.



Nano scientists develop the 'ultimate discovery tool'
Rapid discovery power is similar to what gene chips offer biology


Source: Northwestern University


Summary: The discovery power of the gene chip is coming to nanotechnology. Researchers have figured out how to make combinatorial libraries of nanoparticles in a very controlled way. Some of the nanoparticle compositions have never been observed before on Earth. The tool they are developing could be used to rapidly test millions to billions of different nanoparticles at one time to zero in on the best particle for a specific use. Applications include catalysts, light-harvesting materials, pharmaceuticals and optoelectronic devices.
 

A combinatorial library of polyelemental nanoparticles was developed using Dip-Pen Nanolithography. This novel nanoparticle library opens up a new field of nanocombinatorics for rapid screening of nanomaterials for a multitude of properties. Credit: Peng-Cheng Chen/James Hedrick

The discovery power of the gene chip is coming to nanotechnology. A Northwestern University research team is developing a tool to rapidly test millions and perhaps even billions or more different nanoparticles at one time to zero in on the best particle for a specific use.

When materials are miniaturized, their properties -- optical, structural, electrical, mechanical and chemical -- change, offering new possibilities. But determining what nanoparticle size and composition are best for a given application, such as catalysts, biodiagnostic labels, pharmaceuticals and electronic devices, is a daunting task.

"As scientists, we've only just begun to investigate what materials can be made on the nanoscale," said Northwestern's Chad A. Mirkin, a world leader in nanotechnology research and its application, who led the study. "Screening a million potentially useful nanoparticles, for example, could take several lifetimes. Once optimized, our tool will enable researchers to pick the winner much faster than conventional methods. We have the ultimate discovery tool."

Using a Northwestern technique that deposits materials on a surface, Mirkin and his team figured out how to make combinatorial libraries of nanoparticles in a very controlled way. (A combinatorial library is a collection of systematically varied structures encoded at specific sites on a surface.) Their study will be published June 24 by the journal Science.

The nanoparticle libraries are much like a gene chip, Mirkin says, where thousands of different spots of DNA are used to identify the presence of a disease or toxin. Thousands of reactions can be done simultaneously, providing results in just a few hours. Similarly, Mirkin and his team's libraries will enable scientists to rapidly make and screen millions to billions of nanoparticles of different compositions and sizes for desirable physical and chemical properties.

"The ability to make libraries of nanoparticles will open a new field of nanocombinatorics, where size -- on a scale that matters -- and composition become tunable parameters," Mirkin said. "This is a powerful approach to discovery science."

Mirkin is the George B. Rathmann Professor of Chemistry in the Weinberg College of Arts and Sciences and founding director of Northwestern's International Institute for Nanotechnology.

"I liken our combinatorial nanopatterning approach to providing a broad palette of bold colors to an artist who previously had been working with a handful of dull and pale black, white and grey pastels," said co-author Vinayak P. Dravid, the Abraham Harris Professor of Materials Science and Engineering in the McCormick School of Engineering.

Using five metallic elements -- gold, silver, cobalt, copper and nickel -- Mirkin and his team developed an array of unique structures by varying every elemental combination. In previous work, the researchers had shown that particle diameter also can be varied deliberately on the 1- to 100-nanometer length scale.

Some of the compositions can be found in nature, but more than half of them have never existed before on Earth. And when pictured using high-powered imaging techniques, the nanoparticles appear like an array of colorful Easter eggs, each compositional element contributing to the palette.

To build the combinatorial libraries, Mirkin and his team used Dip-Pen Nanolithography, a technique developed at Northwestern in 1999, to deposit onto a surface individual polymer "dots," each loaded with different metal salts of interest. The researchers then heated the polymer dots, reducing the salts to metal atoms and forming a single nanoparticle. The size of the polymer dot can be varied to change the size of the final nanoparticle.

This control of both size and composition of nanoparticles is very important, Mirkin stressed. Having demonstrated control, the researchers used the tool to systematically generate a library of 31 nanostructures using the five different metals.

To help analyze the complex elemental compositions and size/shape of the nanoparticles down to the sub-nanometer scale, the team turned to Dravid, Mirkin's longtime friend and collaborator. Dravid, founding director of Northwestern's NUANCE Center, contributed his expertise and the advanced electron microscopes of NUANCE to spatially map the compositional trajectories of the combinatorial nanoparticles.

Now, scientists can begin to study these nanoparticles as well as build other useful combinatorial libraries consisting of billions of structures that subtly differ in size and composition. These structures may become the next materials that power fuel cells, efficiently harvest solar energy and convert it into useful fuels, and catalyze reactions that take low-value feedstocks from the petroleum industry and turn them into high-value products useful in the chemical and pharmaceutical industries.

Story Source:
The above post is reprinted from materials provided by Northwestern University. The original item was written by Megan Fellman.

Journal Reference:
Peng-Cheng Chen, Xiaolong Liu, James L. Hedrick, Zhuang Xie, Shunzhi Wang, Qing-Yuan Lin, Mark C. Hersam, Vinayak P. Dravid, Chad A. Mirkin. Polyelemental nanoparticle libraries. Science, 2016 DOI: 10.1126/science.aaf8402.



Probing giant planets' dark hydrogen

Source: Carnegie Institution for Science


Summary: Hydrogen is the most-abundant element in the universe, but there is still so much we have to learn about it. One of the biggest unknowns is its transformation under the extreme pressures and temperatures found in the interiors of giant planets, where it is squeezed until it becomes liquid metal, capable of conducting electricity. New work measures the conditions under which hydrogen undergoes this transition in the lab and finds an intermediate 'dark hydrogen' state.
 

An illustration of the layer of dark hydrogen the team's lab mimicry indicates would be found beneath the surface of gas giant planets like Jupiter, courtesy of Stewart McWilliams. Credit: University of Edinburgh (graphics) and NASA (photos)

Hydrogen is the most-abundant element in the universe. It's also the simplest--sporting only a single electron in each atom. But that simplicity is deceptive, because there is still so much we have to learn about hydrogen.

One of the biggest unknowns is its transformation under the extreme pressures and temperatures found in the interiors of giant planets, where it is squeezed until it becomes liquid metal, capable of conducting electricity. New work published in Physical Review Letters by Carnegie's Alexander Goncharov and University of Edinburgh's Stewart McWilliams measures the conditions under which hydrogen undergoes this transition in the lab and finds an intermediate state between gas and metal, which they're calling "dark hydrogen."

On the surface of giant planets like Jupiter, hydrogen is a gas. But between this gaseous surface and the liquid metal hydrogen in the planet's core lies a layer of dark hydrogen, according to findings gleaned from the team's lab mimicry.

Using a laser-heated diamond anvil cell to create the conditions likely to be found in gas giant planetary interiors, the team probed the physics of hydrogen under a range of pressures from 10,000 to 1.5 million times normal atmospheric pressure and up to 10,000 degrees Fahrenheit.

They discovered this unexpected intermediate phase, which does not reflect or transmit visible light, but does transmit infrared radiation, or heat.

"This observation would explain how heat can easily escape from gas giant planets like Saturn," explained Goncharov.

They also found that this intermediate dark hydrogen is somewhat metallic, meaning it can conduct an electric current, albeit poorly. This means that it could play a role in the process by which churning metallic hydrogen in gas giant planetary cores produces a magnetic field around these bodies, in the same way that the motion of liquid iron in Earth's core created and sustains our own magnetic field.

"This dark hydrogen layer was unexpected and inconsistent with what modeling research had led us to believe about the change from hydrogen gas to metallic hydrogen inside of celestial objects," Goncharov added.

Story Source:
The above post is reprinted from materials provided by Carnegie Institution for Science.

Journal Reference:
R. Stewart McWilliams, D. Allen Dalton, Mohammad F. Mahmood, Alexander F. Goncharov. Optical Properties of Fluid Hydrogen at the Transition to a Conducting State. Physical Review Letters, 2016; 116 (25) DOI: 10.1103/PhysRevLett.116.255501.



Fix for 3-billion-year-old genetic error could dramatically improve genetic sequencing

Source: University of Texas at Austin


Summary: Researchers found a fix for a 3-billion-year-old glitch in one of the major carriers of information needed for life, RNA, which until now produced errors when making copies of genetic information. The discovery will increase precision in genetic research and could dramatically improve medicine based on a person's genetic makeup.
 

Molecular bioscientist Jared Ellefson of the University of Texas at Austin has created a way for RNA to "proofread" copies of genetic information for the first time. This artist's interpretation of the process shows RNA making DNA copies in a droplet of water. Credit: Jared Ellefson, University of Texas at Austin

For 3 billion years, one of the major carriers of information needed for life, RNA, has had a glitch that creates errors when making copies of genetic information. Researchers at The University of Texas at Austin have developed a fix that allows RNA to accurately proofread for the first time. The new discovery, published June 23 in the journal Science, will increase precision in genetic research and could dramatically improve medicine based on a person's genetic makeup.

Certain viruses called retroviruses can cause RNA to make copies of DNA, a process called reverse transcription. This process is notoriously prone to errors because an evolutionary ancestor of all viruses never had the ability to accurately copy genetic material.

The new innovation engineered at UT Austin is an enzyme that performs reverse transcription but can also "proofread," or check its work while copying genetic code. The enzyme allows, for the first time, for large amounts of RNA information to be copied with near perfect accuracy.

"We created a new group of enzymes that can read the genetic information inside living cells with unprecedented accuracy," says Jared Ellefson, a postdoctoral fellow in UT Austin's Center for Systems and Synthetic Biology. "Overlooked by evolution, our enzyme can correct errors while copying RNA."

Reverse transcription is mainly associated with retroviruses such as HIV. In nature, these viruses' inability to copy DNA accurately may have helped create variety in species over time, contributing to the complexity of life as we know it.

Since discovering reverse transcription, scientists have used it to better understand genetic information related to inheritable diseases and other aspects of human health. Still, the error-prone nature of existing RNA sequencing is a problem for scientists.

"With proofreading, our new enzyme increases precision and fidelity of RNA sequencing," says Ellefson. "Without the ability to faithfully read RNA, we cannot accurately determine the inner workings of cells. These errors can lead to misleading data in the research lab and potential misdiagnosis in the clinical lab."

Ellefson and the team of researchers engineered the new enzyme using directed evolution to train a high-fidelity (proofreading) DNA polymerase to use RNA templates. The new enzyme, called RTX, retains the highly accurate and efficient proofreading function, while copying RNA. Accuracy is improved at least threefold, and it may be up to 10 times as accurate. This new enzyme could enhance the methods used to read RNA from cells.

"As we move towards an age of personalized medicine where everyone's transcripts will be read out almost as easily as taking a pulse, the accuracy of the sequence information will become increasingly important," said Andy Ellington, a professor of molecular biosciences. "The significance of this is that we can now also copy large amounts of RNA information found in modern genomes, in the form of the RNA transcripts that encode almost every aspect of our physiology. This means that diagnoses made based on genomic information are far more likely to be accurate. "

In addition to Ellefson and Ellington, authors include Jimmy Gollihar, Raghav Shroff, Haridha Shivram and Vishwanath Iyer. All are affiliated with the Department of Molecular Biosciences at The University of Texas at Austin.

This research was supported by grants from the Defense Advanced Research Projects Agency, National Security Science and Engineering Faculty Fellows, NASA and the Welch Foundation. A provisional patent was filed on the new sequence of the enzyme.

Story Source:
The above post is reprinted from materials provided by University of Texas at Austin.

Journal Reference:
Jared W. Ellefson, Jimmy Gollihar, Raghav Shroff, Haridha Shivram, Vishwanath R. Iyer, Andrew D. Ellington. Synthetic evolutionary origin of a proofreading reverse transcriptase. Science, 2016; 352 (6293): 1590-1593 DOI: 10.1126/science.aaf5409.



Human brain houses diverse populations of neurons, new research shows

Source: University of California - San Diego


Summary: A team of researchers has developed the first scalable method to identify different subtypes of neurons in the human brain. The research lays the groundwork for 'mapping' the gene activity in the human brain and could help provide a better understanding of brain functions and disorders, including Alzheimer's, Parkinson's, schizophrenia and depression.
 

Researchers identified 16 neuronal subtypes by analyzing thousands of individual neurons in six Brodmann areas of a post mortem human brain. (Stock image) Credit: © BillionPhotos.com / Fotolia

A team of researchers has developed the first scalable method to identify different subtypes of neurons in the human brain. The research lays the groundwork for "mapping" the gene activity in the human brain and could help provide a better understanding of brain functions and disorders, including Alzheimer's, Parkinson's, schizophrenia and depression.

By isolating and analyzing the nuclei of individual human brain cells, researchers identified 16 neuronal subtypes in the cerebral cortex -- the brain's outer layer of neural tissue responsible for cognitive functions including memory, attention and decision making. The team, led by researchers at the University of California San Diego, The Scripps Research Institute (TSRI) and Illumina, published their findings in the June 24 online issue of the journal Science.

"We're providing a unified framework to look at and compare individual neurons, which can help us find out how many unique types of neurons exist," said Kun Zhang, bioengineering professor at the University of California, San Diego and a corresponding author of the study.

Researchers can use these different neuronal subtypes to build what Zhang calls a "reference map" of the human brain -- a foundation to understand the differences between a healthy brain and a diseased brain.

"In the future, patients with brain disorders or abnormalities could be diagnosed and treated based on how they differ from the reference map. This is analogous to what's being done with the reference human genome map," Zhang said.

The new study reflects a growing understanding that individual brain cells are unique: they express different types of genes and perform different functions. To better understand this diversity, researchers analyzed more than 3,200 single human neurons in six Brodmann areas, which are regions of the cerebral cortex classified by their functions and arrangements of neurons.

Through an interdisciplinary collaborative effort, the team developed a new method to isolate and sequence individual cell nuclei. TSRI researchers led by neuroscience professor Jerold Chun obtained the samples from a post mortem brain and focused on isolating the neuronal nuclei. Zhang's lab worked with Fluidigm, a manufacturer of microfluidic chips for single-cell studies, to develop a protocol to identify and quantify RNA molecules in individual neuronal nuclei. Scientists at San Diego-based Illumina sequenced the resulting RNA libraries. Researchers led by biochemistry professor Wei Wang at UC San Diego developed algorithms to cluster and identify 16 neuronal subtypes from the sequenced datasets.

Researchers deciphered what types of genes were "turned on" within each nucleus and revealed that various combinations of the 16 subtypes tended to cluster in cortical layers and Brodmann areas, helping explain why these regions look and function differently.

Neurons exhibited many differences in their transcriptomic profiles -- the patterns of genes that are being actively expressed by these cells -- revealing single neurons with shared, as well as unique, characteristics that likely lead to difference in cellular function.

"We're finding new ways to understand the basic building blocks of the brain," said Blue Lake, a postdoctoral researcher in Zhang's lab and a co-first author of the study. "Our study opens the door to look at global gene expression patterns and how that defines cell types within a normal tissue, which can also be used to see what's abnormal in terms of disease or disorders."

In future studies, researchers aim to analyze neurons in other Brodmann areas of the brain and investigate what subtypes exist in other brain regions. They also plan to study neurons from multiple post mortem human brains (this study only involved one) to investigate neuronal diversity among individuals.

Story Source:
The above post is reprinted from materials provided by University of California - San Diego. Note: Materials may be edited for content and length.

Journal Reference:
Kun Zhang et al. Neuronal subtypes and diversity revealed by single-nucleus RNA sequencing of the human brain. Science, June 2016 DOI: 10.1126/science.aaf1204.



'Flower Power': Photovoltaic cells replicate rose petals

Source: (Karlsruhe Institute of Technology


Summary: With a surface resembling that of plants, solar cells improve light-harvesting and thus generate more power. Scientists reproduced the epidermal cells of rose petals that have particularly good antireflection properties and integrated the transparent replicas into an organic solar cell. This resulted in a relative efficiency gain of twelve percent.
 

Biomimetics: the epidermis of a rose petal is replicated in a transparent layer which is then integrated into the front of a solar cell. Credit: Illustration: Guillaume Gomard, KIT

With a surface resembling that of plants, solar cells improve light-harvesting and thus generate more power. Scientists of KIT (Karlsruhe Institute of Technology) reproduced the epidermal cells of rose petals that have particularly good antireflection properties and integrated the transparent replicas into an organic solar cell. This resulted in a relative efficiency gain of twelve percent. An article on this subject has been published recently in the Advanced Optical Materials journal.

Photovoltaics works in a similar way as the photosynthesis of plants. Light energy is absorbed and converted into a different form of energy. In this process, it is important to use a possibly large portion of the sun's light spectrum and to trap the light from various incidence angles as the angle changes with the sun's position. Plants have this capability as a result of a long evolution process -- reason enough for photovoltaics researchers to look closely at nature when developing solar cells with a broad absorption spectrum and a high incidence angle tolerance.

Scientists at the KIT and the ZSW (Center for Solar Energy and Hydrogen Research Baden-Württemberg) now suggest in their article published in the Advanced Optical Materials journal to replicate the outermost tissue of the petals of higher plants, the so-called epidermis, in a transparent layer and integrate that layer into the front of solar cells in order to increase their efficiency.

First, the researchers at the Light Technology Institute (LTI), the Institute of Microstructure Technology (IMT), the Institute of Applied Physics (APH), and the Zoological Institute (ZOO) of KIT as well as their colleagues from the ZSW investigated the optical properties, and above all, the antireflection effect of the epidermal cells of different plant species. These properties are particularly pronounced in rose petals where they provide stronger color contrasts and thus increase the chance of pollination. As the scientists found out under the electron microscope, the epidermis of rose petals consists of a disorganized arrangement of densely packed microstructures, with additional ribs formed by randomly positioned nanostructures.

In order to exactly replicate the structure of these epidermal cells over a larger area, the scientists transferred it to a mold made of polydimethylsiloxane, a silicon-based polymer, pressed the resulting negative structure into optical glue which was finally left to cure under UV light. "This easy and cost-effective method creates microstructures of a depth and density that are hardly achievable with artificial techniques," says Dr. Guillaume Gomard, Group Leader "Nanopothonics" at KIT's LTI.

The scientists then integrated the transparent replica of the rose petal epidermis into an organic solar cell. This resulted in power conversion efficiency gains of twelve percent for vertically incident light. At very shallow incidence angles, the efficiency gain was even higher. The scientists attribute this gain primarily to the excellent omnidirectional antireflection properties of the replicated epidermis that is able to reduce surface reflection to a value below five percent, even for a light incidence angle of nearly 80 degrees. In addition, as examinations using a confocal laser microscope showed, every single replicated epidermal cell works as a microlense. The microlense effect extends the optical path within the solar cell, enhances the light-matter-interaction, and increases the probability that the photons will be absorbed.

"Our method is applicable to both other plant species and other PV technologies," Guillaume Gomard explains. "Since the surfaces of plants have multifunctional properties, it might be possible in the future to apply multiple of these properties in a single step." The results of this research lead to another basic question: What is the role of disorganization in complex photonic structures? Further studies are now examining this issue with the perspective that the next generation of solar cells might benefit from their results.

Story Source:
The above post is reprinted from materials provided by (Karlsruhe Institute of Technology.

Journal Reference:
Ruben Hünig, Adrian Mertens, Moritz Stephan, Alexander Schulz, Benjamin Richter, Michael Hetterich, Michael Powalla, Uli Lemmer, Alexander Colsmann, Guillaume Gomard. Flower Power: Exploiting Plants' Epidermal Structures for Enhanced Light Harvesting in Thin-Film Solar Cells. Advanced Optical Materials, 2016; DOI: 10.1002/adom.201600046.



Eating air, making fuel
Scientists engineer bacteria to create sugar from the greenhouse gas carbon dioxide

Source: Weizmann Institute of Science


Summary: Is it possible to "reprogram" an organism that is found higher in the food chain, which consumes sugar and releases carbon dioxide, so that it will consume carbon dioxide from the environment and produce the sugars it needs to build its body mass? Scientists now report that they have engineered bacteria to create sugar from the greenhouse gas carbon dioxide.
 

Weizmann Institute scientists engineer bacteria to create sugar from the greenhouse gas carbon dioxide. Credit: Weizmann Institute of Science

All life on the planet relies, in one way or another, on a process called carbon fixation: the ability of plants, algae and certain bacteria to "pump" carbon dioxide (CO2) from the environment, add solar or other energy and turn it into the sugars that are the required starting point needed for life processes. At the top of the food chain are different organisms (some of which think, mistakenly, that they are "more advanced") that use the opposite means of survival: they eat sugars (made by photosynthetic plants and microorganisms) and then release carbon dioxide into the atmosphere. This means of growth is called "heterotrophism." Humans are, of course, heterotrophs in the biological sense because the food they consume originates from the carbon fixation processes of nonhuman producers.

Is it possible to "reprogram" an organism that is found higher in the food chain, which consumes sugar and releases carbon dioxide, so that it will consume carbon dioxide from the environment and produce the sugars it needs to build its body mass? That is just what a group of Weizmann Institute of Science researchers recently did. Dr. Niv Antonovsky, who led this research in Prof. Ron Milo's lab at the Institute's Plant and Environmental Sciences Department, says that the ability to improve carbon fixation is crucial for our ability to cope with future challenges, such as the need to supply food to a growing population on shrinking land resources while using less fossil fuel.

The Institute scientists rose to this challenge by inserting the metabolic pathway for carbon fixation and sugar production (the so called Calvin cycle) into the bacterium E. coli, a known "consumer" organism that eats sugar and releases carbon dioxide.

The metabolic pathway for carbon fixation is well known, and Milo and his group reckoned that, with proper planning, they would be able to attach the genes containing the information for building it into the bacterium's genome. Yet the main enzyme used in plants to fix carbon, RuBisCO, utilizes as a substrate for the CO2 fixation reaction a metabolite which is toxic for the bacterial cells. Thus the design had to include precisely regulating the expression levels of the various genes across this multistep pathway.

In one way the team's well-thought-out plan was a resounding success: The bacteria did indeed produce the carbon fixation enzymes, and these were functional. But the machinery, as a whole, did not "deliver the goods." Even though the carbon fixation machinery was expressed, the bacteria failed to use CO2 for sugar synthesis, relying instead on an external supply of sugar. "Of course, we were dealing with an organism that has evolved over millions of years to eat sugar, not CO2," says Antonovsky. "So we turned to evolution to help us create the system we intended."

Antonovsky, Milo and the team, including Shmuel Gleizer, Arren Bar-Even, Yehudit Zohar, Elad Herz and others, next designed tanks called "chemostats," in which they grew the bacteria, gradually nudging them into developing an appetite for CO2. Initially, along with ample bubbles of CO2, the bacteria in the tanks were offered a large amount of pyruvate, which is an energy source, as well as barely enough sugar to survive. Thus, by changing the conditions of their environment and stressing them, the scientists forced the bacteria to learn, by adaptation and development, to use the more abundant material in their environment. A month went by, and things remained fairly static. The bacteria seemed to not "get the hint." But at around a month and a half, some bacteria showed signs of doing more than "just surviving." By the third month the scientists were able to wean the evolved bacteria from the sugar and raise them on CO2 and pyruvate alone. Isotope labeling of the carbon dioxide molecules revealed that the bacteria were indeed using CO2 to create a significant portion of their body mass, including all the sugars needed to make the cell.

When the scientists sequenced the genomes of the evolved bacteria, they found many changes scattered throughout the bacterial chromosomes. "They were completely different from what we had predicted," says Milo. "It took us two years of hard work to understand which of these are essential and to unravel the 'logic' involved in their evolution." Repeating the experiment (and again waiting months) gave the scientists essential clues for identifying the mutations necessary for changing the E. coli diet from one based on sugar to one using carbon dioxide.

Milo said, "The ability to program or reengineer E. coli to fix carbon could give researchers a new toolbox for studying and improving this basic process." Although currently the bacteria release CO2 back into the atmosphere, the team envisions that in the future their insights might be applied to creating microorganisms that soak up atmospheric CO2 and convert it into stored energy or to achieving crops with carbon fixing pathways, resulting in higher yields and better adaption to feeding humanity.

Story Source:
The above post is reprinted from materials provided by Weizmann Institute of Science.

Journal Reference:
Niv Antonovsky et al. Sugar Synthesis from CO2 in Escherichia coli. Cell, June 2016 DOI: 10.1016/j.cell.2016.05.064.



Researchers offer new theory on how climate affects violence.

Climate impacts life strategies, time orientation, self-control

Source: Ohio State University


Summary: Researchers have long struggled to explain why some violent crime rates are higher near the equator than other parts of the world. Now, a team of researchers has developed a model that could help explain why.
 

The General Aggression Model suggests hot temperatures make people uncomfortable and irritated, which makes them more aggressive.Credit: © malven / Fotolia

Researchers have long struggled to explain why some violent crime rates are higher near the equator than other parts of the world. Now, a team of researchers have developed a model that could help explain why.

This new model goes beyond the simple fact that hotter temperatures seem to be linked to more aggressive behavior.

The researchers believe that hot climates and less variation in seasonal temperatures leads to a faster life strategy, less focus on the future, and less self-control -- all of which contribute to more aggression and violence.

"Climate shapes how people live, it affects the culture in ways that we don't think about in our daily lives," said Brad Bushman, co-author of the study and professor of communication and psychology at The Ohio State University.

Paul van Lange, lead author of the study and a professor of psychology at the Vrije Universiteit Amsterdam (VU) added, "We believe our model can help explain the impact of climate on rates of violence in different parts of the world."

The researchers, which included Maria I. Rinderu of VU, call the new model CLASH (CLimate Aggression, and Self-control in Humans). They describe the CLASH model in an online article in the journal Behavioral and Brain Sciences.

Many studies have shown that levels of violence and aggression are higher in hot climates, according to the researchers.

"But the two leading explanations of why that is so aren't satisfactory," Bushman said.

The General Aggression Model (which Bushman helped develop) suggests hot temperatures make people uncomfortable and irritated, which makes them more aggressive. "But that doesn't explain more extreme acts, such as murder," he said.

Another explanation (Routine Activity Theory) is that people are outdoors and interacting more with others when the weather is warm, which leads to more opportunities for conflict. But that doesn't explain why there's more violence when the temperature is 95 degrees F (35 °C) than when it is 75 degrees F (24 °C) -- even though people might be outside under both circumstances.

The CLASH model states that it is not just hotter temperatures that lead to more violence -- it is also climates that have less seasonal variation in temperature.

"Less variation in temperature, combined with heat, brings some measure of consistency to daily life," Rinderu said.

That means there is less need to plan for large swings between warm and cold weather. The result is a faster life strategy that isn't as concerned about the future and leads to less need for self-control.

"Strong seasonal variation in temperature affects culture in powerful ways. Planning in agriculture, hoarding, or simply preparing for cold winters shapes the culture in many ways, often with people not even noticing it. But it does shape how much a culture values time and self-control," Van Lange said.

"If there is less variation, you're freer to do what you want now, because you're not preparing foods or chopping firewood or making winter clothes to get you through the winter. You also may be more concerned with the immediate stress that comes along with parasites and other risks of hot climates, such as venomous animals."

People living in these climates are oriented to the present rather than the future and have a fast life strategy -- they do things now.

"We see evidence of a faster life strategy in hotter climates with less temperature variation -- they are less strict about time, they have less use of birth control, they have children earlier and more often," Bushman said.

With a faster life strategy and an orientation toward the present, people have to practice less self-control, he said. That can lead people to react more quickly with aggression and sometimes violence.

The theory is not deterministic and isn't meant to suggest that people in hotter, consistent climates can't help themselves when it comes to violence and aggression.

"How people approach life is a part of culture and culture is strongly affected by climate," Van Lange said. "Climate doesn't make a person, but it is one part of what influences each of us. We believe it shapes the culture in important ways," he said.

Since CLASH is a new theory, studies have to be done to prove it is correct. But Bushman said a lot of evidence already suggests that the theory may be on to something.

"We believe CLASH can help account for differences in aggression and violence both within and between countries around the world," he said. "We think it provides a strong framework for understanding the violence differences we see around the world."

Story Source:
The above post is reprinted from materials provided by Ohio State University. The original item was written by Jeff Grabmeier.

Journal Reference:
Paul A. M. Van Lange, Maria I. Rinderu, and Brad J. Bushman. Aggression and Violence Around the World: A Model of CLimate, Aggression, and Self-control in Humans (CLASH). Behavioral and Brain Sciences, June 2016.
 

Source: S.D.Tech

 

Courtesy: Researcher