Tag: Life Sciences

Can Bats Think Ahead of Time?

Written by Hilary on 25 July 2024. Posted in Newsroom.

TAU researchers discover that bats have episodic memory and plan ahead

Researchers at Tel Aviv University tracked free-ranging Egyptian fruit bats from a colony based in the TAU’s I. Meier Segals Garden for Zoological Research to answer a long-standing scientific question: Do animals have high and complex cognitive abilities, previously attributed only to humans? In particular, the study focused on the traits of episodic memory, mental time travel, planning ahead, and delayed gratification, arriving at highly thought-provoking conclusions.

The study was led by Prof. Yossi Yovel and Dr. Lee Harten from the School of Zoology and Sagol School of Neuroscience at Tel Aviv University. Other researchers included: Xing Chen, Adi Rachum, Michal Handel, and Aya Goldstein from the School of Zoology, Lior de Marcas from the Sagol School of Neuroscience, and Maya Fenigstein Levi and Shira Rosencwaig from the National Public Health Laboratory of Israel’s Ministry of Health. The paper was published in Current Biology.

Prof. Yossi Yovel.

Prof. Yovel: “For many years the cognitive abilities to recall personal experiences (episodic memory) and plan ahead were considered exclusive to humans. But more and more studies have suggested that various animals also possess such capabilities. Still, nearly all of these studies were conducted under laboratory conditions, since field studies on these issues are difficult to perform. Attempting to test these abilities in wild animals, we designed a unique experiment relying on the colony of free-ranging fruit bats based in TAU’s I. Meier Segals Garden for Zoological Research”.

How Bats Keep Track of Food Resources

The researchers assumed that bats depending on fruit trees for their survival would need to develop an ability to track the availability of food both spatially (where are the fruit trees?) and over time (when does each tree give fruit?). Navigating through landscapes with numerous fruit and nectar trees, they would need to mentally track the resources in order to revisit them at the appropriate time. To test this hypothesis, a tiny high-resolution GPS tracker was attached to each bat, enabling the documentation of flight routes and trees visited for many months. The vast data collected in this way were thoroughly analyzed, producing some amazing results.

The first research question was: Do bats form a time map in their minds? To explore this issue, the researchers prevented the bats from leaving the colony for varying periods of time, from one day to a week. Dr. Harten: “We wanted to see whether the bats could tell that time had elapsed and behave accordingly. We found that after one day of captivity, the bats would return to trees visited on the previous night. However, when a whole week had gone by, the older bats, based on past experience, avoided trees that had stopped bearing fruit in the interval. In other words: they were able to estimate how much time had passed since their last visit to each tree and knew which trees bore fruit for a short time and were no longer worth visiting. Young, inexperienced bats were unable to do this, indicating that this is an acquired skill that must be learned”.

While the first research question looked at past experiences, the second dealt with the future: Do the bats exhibit future-oriented behaviors? Are they capable of planning ahead? To address this issue the researchers observed each bat’s route to the first tree of the evening, possibly indicative of plans made before leaving the colony. Chen Xing: “We found that usually the bats fly directly to a specific tree they know, sometimes 20 or 30 minutes away. Being hungry, they fly faster when that tree is further away, suggesting they plan where they are heading.

Moreover, focused on their chosen target, they will pass by other trees, even good sources visited just yesterday – indicating a capacity for delayed gratification. We also found that the first bats to leave the colony choose trees bearing fruits rich in sugar, while the bats that leave later seek proteins.” All these findings suggest that the bats plan their foraging before they leave the colony, and know exactly where they are flying and what kind of nourishment they are looking for.

Rethinking Intelligence in Animals

Prof. Yovel: “The cognitive gap between humans and animals is one of the most fascinating issues in science. Our study demonstrates that fruit bats are capable of quite a complex decision-making process involving the three questions indicative of cognitive abilities: Where? (each tree’s location); When? (when the tree bears fruit); and What? (the nourishment it provides – sugar vs. proteins). Once again we find that the gap is not cleat-cut, and that humans are not as unique as some might think. Apparently, humans and animals are all located on a spectrum, with almost any human ability found in animals as well”.

Tel Aviv University Shatters Limits with Self-Repairing Glass

Written by Hilary on 26 June 2024. Posted in Newsroom.

TAU researchers create transparent, self-repairing adhesive glass that forms in contact with water.

Researchers from TAU have created a new type of glass with unique and even contradictory properties, such as being a strong adhesive (sticky) and incredibly transparent at the same time. The glass, which forms spontaneously when in contact with water at room temperature, could revolutionize in an array of diverse industries such as optics and electro-optics, satellite communication, remote sensing and biomedicine. The glass has been discovered by a team of researchers from Israel and the world, led by PhD student Gal Finkelstein-Zuta and Prof. Ehud Gazit from the Shmunis School of Biomedicine and Cancer Research at the Faculty of Life Sciences and the Department of Materials Science and Engineering at the Faculty of Engineering at TAU. The research results were published last week in the prestigious scientific journal Nature.

“In our laboratory, we study bio-convergence and specifically use the wonderful properties of biology to produce innovative materials”, explains Prof. Gazit. “Among other things, we study sequences of amino acids, which are the building blocks of proteins. Amino acids and peptides have a natural tendency to connect and form ordered structures with a defined periodic arrangement, but during the research, we discovered a unique peptide that behaves differently from anything we know: it didn’t form any ordered pattern but an amorphous, disordered one, that describes glass”.

(Left to right) Gal Finkelstein-Zuta and Prof. Ehud Gazit.

Just Add Water

At the molecular level, glass is a liquid-like substance that lacks order in its molecular structure. Still, its mechanical properties are solid-like. Glass is usually manufactured by rapidly cooling molten materials and “freezing” them in this state before they are allowed to crystallize, resulting in an amorphous state that allows unique optical, chemical and mechanical properties – alongside durability, versatility, and sustainability. The researchers from TAU discovered that the aromatic peptide, which consists of a three-tyrosine sequence (YYY), forms a molecular glass spontaneously, upon evaporation of an aqueous solution, under room-temperature conditions.

“The commercial glass we all know is created by the rapid cooling of molten materials, a process called vitrification”, says Gal Finkelstein-Zuta. “The amorphous liquid-like organization should be fixed before it arranges in a more energy-efficient way as in crystals, and for that energy is required – it should be heated to high temperatures and cooled down immediately. On the other hand, the glass we discovered made of biological building blocks, forms spontaneously at room temperature, without the need for energy such as high heat or pressure. Just dissolve a powder in water – just like making Kool-Aid, and the glass will form. For example, we made lenses from our new glass. Instead of undergoing a lengthy process of grinding and polishing, we simply dripped a drop onto a surface, where we control its curvature – and hence its focus – by adjusting the solution volume alone”.

Solid peptide glass after preparation.

The properties of the innovative glass from TAU are unique in the world – and even contradict each other: it is very hard, but it can repair itself at room temperature; It is a strong adhesive, and at the same time, it is transparent in a wide spectral range, ranging from the visible light to the mid-infrared range.

An Unbreakable Marvel

“This is the first time anyone has succeeded in creating molecular glass under simple conditions”, says Prof. Gazit, “but not less important than that are the properties of the glass we created. It is a very special glass. On the one hand, it is very strong and on the other hand, very transparent – much more transparent than ordinary glass. The normal silicate glass we all know is transparent in the visible light range, the molecular glass we created is transparent deep into the infrared range. This has many uses in fields such as satellites, remote sensing, communications and optics. It is also a strong adhesive, it can glue different glasses together, and at the same time, can repair cracks that are formed in it. It is a set of properties that do not exist in any glass in the world, which has great potential in science and engineering, and we got all this from a single peptide – one little piece of protein”.

Global Coral Crisis: Deadly Sea Urchin Disease Discovered

Written by Hilary on 22 May 2024. Posted in Newsroom.

TAU Researchers Found the Cause of Sea Urchin Deaths in the Red Sea, Potentially Threatening Coral Reefs Worldwide.

Sea urchin mortalities on Reunion Island. Photo credit: Jean-Pascal Quod.

The researchers estimate that since it broke out in December 2022, the epidemic has annihilated most of the sea urchin populations (of the species affected by the disease) in the Red Sea, as well as an unknown number of sea urchins, estimated at hundreds of thousands, worldwide. Sea urchins are considered the ‘gardeners’ of coral reefs, feeding on the algae that compete with the corals for sunshine – and their disappearance can severely impact the delicate balance on coral reefs globally. The researchers note that since the discovery of the epidemic in Eilat’s coral reefs, the two species of sea urchins previously most dominant in the Gulf of Eilat have vanished completely.

The Research Team. Photo credit: Tel Aviv University.

The study was led by Dr. Omri Bronstein from the School of Zoology and the Steinhardt Museum of Natural History (SMNH), together with research students Lachan Roth, Gal Eviatar, Lisa Schmidt, and May Bonomo, as well as Dr. Tamar Feldstein-Farkash from the SMNH. Research partners throughout the region and Europe also took part in the study, which encompassed thousands of kilometers of coral reefs. The alarming results were published in the leading scientific journal Current Biology.

Deadly Urchin Pathogen Found

By using molecular-genetic tools, the research group at TAU was able to identify the pathogen responsible for the mass mortality of sea urchins of the species Diadema setosum in the Red Sea: a scuticociliate parasite most similar to Philaster apodigitiformis. The researchers explain that this unicellular organism was also responsible for the reoccurring mass mortality of Diadema antillarum in the Caribbeans about two years ago, following the notorious 1983 sea urchin population collapse there which led to a catastrophic phase shift of the coral reef.

Infected sea urchin on Reunion Island. Photo credit: Jean-Pascal Quod.

As noted, in December 2022, Dr. Bronstein was the first researcher to identify mass mortality of sea urchins of the species Diadema setosum – the long-spined black sea urchins that were very common in the northern Gulf of Eilat, Jordan, and Sinai. Dr. Bronstein and his team also found that the epidemic was lethal for other, closely related sea urchins from the genus Echinothrix. These results suggest that the once most abundant and significant seabed herbivores in the region are now practically gone. Thousands of sea urchins died a quick and violent death – within two days a healthy sea urchin turned into a bear skeleton with no tissues or spines, and most were devoured by predators as they were dying, unable to defend themselves. According to estimates, today only a few individuals of the affected sea urchin species remain throughout the coral reefs of the Gulf of Aqaba.

The sea urchin Diadema setosum before (left) and after (right) mortality. The white skeleton is exposed following tissue disintegration and loss of spines. Photo credit: Tel Aviv University.

Dr. Bronstein explains that sea urchins in general, and specifically diadematoids (the sea urchin family affected by the disease), are considered key species essential for the healthy functioning of coral reefs. Acting as the reef’s ‘gardeners’, the sea urchins feed on the algae that compete with the corals for sunshine, and prevent them from taking over and suffocating the corals.

According to Dr. Bronstein, the most significant and widely studied mass mortality of sea urchins to date occurred in 1983, when a mysterious disease spread through the Caribbeans, killing most sea urchins of the species Diadema antillarum – relatives of Eilat’s sea urchins. Consequently, the algae spread uncontrollably, blocking the sunlight from the corals, and the entire reef was transformed from a coral reef into an algae field. Moreover, even though the mass mortality event in the Caribbeans occurred 40 years ago, both the corals and the sea urchin populations never fully recovered, with repeated mortality events observed through the years.

The latest Caribbean outbreak in 2022 killed surviving populations and individuals from the former mortality events. This time, however, researchers had the scientific and technological tools to decipher the forensic evidence. A research group from Cornell University was able to identify the responsible pathogen, a scuticociliate parasite.

‘A Growing Ecological Crisis’

Dr. Bronstein emphasizes: “This is a growing ecological crisis, threatening the stability of coral reefs on an unprecedented scale. Apparently, the mass mortality we identified in Eilat back in 2023 has spread along the Red Sea and beyond – to Oman, and even as far as Reunion Island in the Indian Ocean.

The deadly pathogen is carried by water and can affect vast areas in a very short time. Even sea urchins raised in seawater systems at the Interuniversity Institute for Marine Sciences in Eilat, or at the Underwater Observatory, were infected and died, after the pathogen got in through the recirculating seawater system. As noted, death is quick and violent. For the first time, our research team was able to document all stages of the disease – from infection to the inevitable death – with a unique video system installed at the Interuniversity Institute for Marine Sciences in Eilat.

Moreover, until recently, only one species of sea urchins was known to be impacted by this pathogen – the Caribbean species. Today we know that additional species are susceptible to the disease – all belonging to the same family of the most significant sea urchin herbivores on coral reefs”.

Four healthy sea urchin species on Reunion Island. Photo credit: Jean-Pascal Quod.

Dr. Bronstein adds: “In our study we also demonstrated that the epidemic is spreading along routes of human transportation in the Red Sea. The best example is the wharf in Nueiba in Sinai, where the ferry from the Jordanian city of Aqaba docks. When we published our report last year, we already knew of sea urchin mortalities in Aqaba but had not yet identified signs of it in Sinai. The first spot in which we ultimately did identify mortality in Sinai was next to this wharf in Nueiba. Two weeks later the epidemic had already reached Dahab, about 70km further south. The scene underwater is almost surreal: seeing a species that was so dominant in a certain environment simply erased in a matter of days. Thousands of skeletons rolling on the sea bottom, crumbling and vanishing in a very short time so that even evidence for what has occurred is hard to find”.

Can We Stop the Sea Urchin Plague?

According to Dr. Bronstein, there is currently no way to help infected sea urchins or vaccinate them against the disease. We must, however, quickly establish broodstock populations of endangered species in cultivation systems disconnected from the sea – so that in the future we will be able to reintroduce them into the natural environment.

“Unfortunately, we cannot repair nature, but we can certainly change our own behavior. First of all, we must understand what caused this outbreak at this time. Is the pathogen transported unknowingly by seacraft? Or has it always been here, erupting now due to a change in environmental conditions? These are precisely the questions we are working on now”.

Wake-Up Call: Global Warming and Deforestation Threaten Wildlife

Written by Hilary on 21 May 2024. Posted in Newsroom.

A New TAU Study Shows that Global Warming and Deforestation Could Cause Mass Animal Extinctions.

A joint study by TAU and the University of Colorado (CU) states that the combination of global warming and extreme heat events, alongside the continued expansion of deforestation in the world, may be devastating for many species of animals, especially those that know how to climb trees. As part of the study, the researchers focused on lizards and showed that following the effects of climate change, they will seek refuge from the hot ground by spending a lot of time on trees. However, due to human-related activities, such as deforestation, urbanization and the expansion of agricultural lands at the expense of natural lands, the availability of trees in the areas where the lizards live will decrease, and this may lead to the collapse of many populations.

The research was conducted under the leadership of doctoral student Omer Zlotnick from the laboratory of Dr. Ofir Levy at the School of Zoology, the Wise Faculty of Life Sciences and the Steinhardt Museum of Natural History at TAU and in collaboration with Dr. Keith Musselman from CU. The study was published in the journal Nature Climate Change.

Climate Crisis: Animals Seeking Comfort in Trees

The researchers explain that the climate crisis and global warming force animals to search for more comfortable places to stay to escape the extreme heat, just as we look for a shady area on a hot day. For climbing animals, trees can serve as a comfortable and pleasant refuge. One of the reasons for this is that the farther you get from the ground, the lower the air temperature gets, and the stronger the wind becomes. Therefore, on hot days, for example, animals can climb up trees to escape from the hot ground.

The importance of trees, then, is expected to increase as the climate warms. The problem is that in many places in the world, the density of trees is decreasing, mainly due to phenomena such as deforestation and the expansion of the use of trees for various purposes such as construction, etc. This phenomenon creates a situation where, on the one hand, due to climate change, animals will depend more on trees for their survival, while on the other hand, the destruction of habitats will lead to a decrease in the availability of trees.

Lizards’ Habitat Loss

Doctoral student Omer Zlotnik: “As part of the research, we wanted to examine how the combined effect of these two processes would be on animals. Specifically, we focused on lizards because they are very dependent on their environment to maintain a normal body temperature, and a lack of comfortable places to stay can affect them dramatically. In the study, we used a computer simulation to simulate where the lizard should be, in the sun, in the shade, or on the tree, every minute for 20 years, under the climate conditions that existed in the past and under those expected in the future. Using the simulation, we examined how populations of lizards would be affected by climate change when trees are available and how their situation would change following the felling of trees in their habitat”.

Left to right – Dr. Ofir Levy & Omer Zlotnick

The results showed that, in general terms, climate change is going to benefit many lizard populations. In most places, the expected warming will allow lizards to be active longer throughout the day and the year, as there will be fewer times when it is too cold to come out of their burrows. However, when climate change occurs at the same time as the felling of trees, the trend is likely to reverse, so that many lizard populations may collapse. In areas with a warm climate, climate change, even if no trees are cut down, is expected to harm lizard populations, and cutting down trees will make the situation even worse.

“What’s really interesting about lizards is that they just need to be able to move a short distance around the tree trunk to get to a very different climate and habitat environment”, said Keith Musselman, an assistant professor in the Department of Geography and CU Boulder’s Institute of Arctic and Alpine Research.

Musselman: “These microhabitats are particularly important when we think about how we modify our natural environment and make conservation decisions”.

Dr. Ofir Levy concludes: “Our research focused on lizards, but it actually demonstrates a broader problem that is relevant to many species of animals. Our results demonstrate that trees are crucially important to the ability of animals to cope with climate change, and in many cases, their availability can be, for the animals, the difference between crawling and collapsing. Our research proves how important it is to preserve forested areas and trees in general, especially in light of the changing climate. As part of the research, we also provide more practical tools for decision-makers, such as the height or density of trees required in different areas. We hope that this research will be used to build more effective programs for the conservation and restoration of natural areas so that we can provide the animals with what they need to survive”.

Go Fish: Decline in Poleward-Moving Fish

Written by AUFTAU on 4 April 2024. Posted in Newsroom.

An extensive international study led by researchers from Tel Aviv University found a decline in the abundance of marine fish species that rapidly move toward the poles to escape rising sea temperatures. The researchers explain that many animal species are currently moving toward cooler regions as a result of global warming, but the velocity of such range shifts varies immensely for different species. Examining thousands of populations from almost 150 fish species, the researchers show that contrary to the prevailing view, rapid range shifts coincide with widescale population declines. According to the study, on average, a poleward shift of 17km per year may result in a decline of 50% in the abundance of populations. The international study was led by Ph.D. student Shahar Chaikin and Prof. Jonathan Belmaker from the School of Zoology in the Wise Faculty of Life Sciences and the Steinhardt Museum of Natural History at Tel Aviv University. The paper was published in the leading scientific journal Nature Ecology & Evolution. For the first time, the new study correlated two global databases: (1) a database that tracks fish population size over time, and (2) a database that compiles range shift velocities among marine fishes. Altogether, 2,572 fish populations belonging to 146 species were studied, mostly from the Atlantic and Pacific Oceans in the Northern Hemisphere.

Left to right - Prof. Jonathan Belmaker Shahar Chaikin

Left to right – Prof. Jonathan Belmaker and Shahar Chaikin

Off the Hook

Prof. Belmaker explains: “We know that climate change causes animal species to move – northward, southward, upwards, or downwards – according to their location relative to cooler regions. In the mountains they climb upwards, in the oceans they dive deeper, in the Southern Hemisphere they move south toward Antarctica, and in the Northern Hemisphere, they move north toward the North Pole. In the present study we wanted to see what happens to species that move from one place to another: do they benefit by increased survivability, or are they in fact harmed by the shift – which was initially caused by greater vulnerability to climate change? We found that the faster fish shift toward the poles, the faster their abundance declines. Apparently, it is difficult for these populations to adapt to their new surroundings”.

PhD student Chaikin: “We found that species shifting their geographical range more rapidly towards the poles, are in fact more likely to lose their abundance (e.g. European seabass). Additional findings show differences between populations that are closer to or further from the poles – within the geographical range of a particular species. While it might have been assumed that populations closer to the cooler polar margins of the species range would be less affected by climate change, we found that the opposite is true: fast poleward range shifts of populations from higher latitudes resulted in a more rapid decline in abundance compared to equatorial populations of the same species”.

The researchers highlight that the new findings can and should guide environmental decisionmakers, by enabling a reevaluation of the conservation status of various species and populations. The study’s results suggest that populations exhibiting rapid poleward range shifts require close monitoring and careful management. Thus, for example, pressures that threaten their survival can be mitigated through measures like fishing limits. Prof. Belmaker: “The common belief is that rapid range shifts safeguard a species against local population decline. But in this study, we found that the opposite is true. Apparently, species rapidly shifting their range in search of cooler temperatures do so because they are more vulnerable to climate change, and consequently require special attention. Last year we published another study that focused on local fish species along Israel’s coastline, which resulted in similar findings: species that move towards deeper and cooler habitats in the face of rising water temperatures exhibit declining populations. In the next stage of our research, we intend to investigate this causal relationship in additional marine species, other than fish”.

Do Viruses Have Consciousness?

Written by AUFTAU on 17 March 2024. Posted in Newsroom.

Bacteria-Targeting Viruses Adapt, Improving their Decision-Making.

Researchers from the Shmunis School of Biomedicine and Cancer Research at Tel Aviv University have deciphered a novel complex decision-making process that helps viruses choose to turn nasty or stay friendly to their bacterial host. In a new paper, they describe how viruses co-opt a bacterial immune system, intended to combat viruses like themselves, in this decision-making process. The study was led by Polina Guler, a PhD student in Prof. Avigdor Eldar’s lab, in addition to other lab members, at the Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences. The paper was published in Nature Microbiology.

All-You-Can-Eat Bacteriophage

Bacteriophages, also known as phages, are types of viruses that infect bacteria and use the infected bacteria to replicate and spread. Even though the word ‘bacteriophage,’ meaning ‘bacteria devouring’ in ancient Greek, suggests destruction, many phages can adopt a “sleeping” mode, in which the virus incorporates itself into the bacterial genome. In fact, in this mode of action, the virus can even have a symbiotic relationship with the bacteria, and its genes can help its host prosper. In general, Eldar explains that phages usually prefer to stay in the “sleeping”, dormant mode, in which the bacteria “cares” for their needs and helps them safely replicate. Previous research published by the Eldar lab has shown that the phages’ decision-making uses two kinds of information to decide whether to stay dormant or turn violent: the “health status” of their host and signals from outside indicating the presence of other phages around.

“A phage can’t infect a cell already occupied by another phage. If the phage identifies that its host is compromised but also receives signals indicating the presence of other phages in the area, it opts to remain with its current host, hoping for recovery. If there is no outside signal, the phage ‘understands’ that there might be room for it in another host nearby and it’ll turn violent, replicate quickly, kill the host, and move on to the next target”, Eldar explains.

Death by Phage

The new study deciphers the mechanism that enables the virus to make these decisions. “We discovered that in this process the phage actually uses a system that the bacteria developed to kill phages”, says Guler. If it does not sense a signal from other phages—indicating that it has a good chance of finding new hosts—the phage activates a mechanism that disables the defense system. “The phage switches to its violent mode, and with the defense system neutralized, it is able to replicate and kill its host”, describes Guler. “If the phage senses high concentrations of the signal, instead of disabling the defense system, it utilizes its defense activity in order to turn on its dormant mode”. “The research revealed a new level of sophistication in this arms race between bacteria and viruses,” adds Eldar. Most bacterial defense systems against phages were studied in the context of viruses that are always violent. Far less is known about the mechanisms of attacks and interaction with viruses that have a dormant mode. “The bacteria also have an interest in keeping the virus in the dormant mode, first and foremost to prevent their own death, and also because the genes of the dormant phage might even contribute to bacterial functions,” says Eldar. “This finding is important for several reasons. One reason is that some bacteria, such as those causing the cholera disease in humans, become more violent if they carry dormant phages inside them – the main toxins that harm us are actually encoded by the phage genome,” explains Eldar. “Another reason is that phages can potentially serve as replacements to antibiotics against pathogenic bacteria. Finally, phage research may lead to better understanding of viruses in general and many human-infecting viruses can also alternate between dormant and violent modes”.

Unlocking Quantum Mysteries with Pendula

Written by AUFTAU on 17 March 2024. Posted in Newsroom.

A recent study conducted at Tel Aviv University has devised a large mechanical system that operates under dynamical rules akin to those found in quantum systems. The dynamics of quantum systems, composed of microscopic particles like atoms or electrons, are notoriously difficult, if not impossible, to observe directly. However, this new system allows researchers to visualize phenomena occurring in specialized “topological” materials through the movement of a system of coupled pendula. The research is a collaboration between Dr. Izhar Neder of the Soreq Nuclear Research Center, Chaviva Sirote-Katz of the Department of Biomedical Engineering, Dr. Meital Geva and Prof. Yair Shokef of the School of Mechanical Engineering, and Prof. Yoav Lahini and Prof. Roni Ilan of the School of Physics and Astronomy at Tel Aviv University and was recently published in the Proceedings of the National Academy of Sciences of the USA (PNAS).

Exploring Quantum Wave Phenomena Quantum mechanics governs the microscopic world of electrons, atoms and molecules. An electron, which is a particle that moves in an atom or in a solid, may have properties that give rise to wave-like phenomena. For instance, it may demonstrate a probability of dispersing in space similar to waves spreading out in a pool after a stone is thrown in, or the capability to exist simultaneously in more than one place. Such wave-like properties lead to a unique phenomenon that appears in some solid isolators, where even though there is no electric current through them, and the electrons do not move due to an external electric voltage, the internal arrangement of the material shows up in a state referred to as “topological”. This means that the wave of electrons possesses a quantity that can “close on itself” in different ways, somewhat like the difference between a cylinder and a Möbius strip. This “topological” state of the electrons, for which the 2016 Nobel Prize in Physics was awarded, is considered a new state of matter and attracts much current research.

Chaviva Sirote-Katz Despite the theoretical interest, there is a limitation in measuring these phenomena in quantum systems. Due to the nature of quantum mechanics, one cannot directly measure the electron’s wave function and its dynamical evolution. Instead, researchers indirectly measure the wave-like and topological properties of electrons in materials, for instance by measuring the electrical conductivity at the edges of solids. In the current study, the researchers considered the possibility of constructing a sufficiently large mechanical system that would adhere to dynamical rules akin to those found in quantum systems, and in which they could directly measure everything. To this end, they built an array of 50 pendula, with string lengths that slightly varied from one pendulum to the other. The strings of each neighboring pair of pendula were connected at a controlled height, such that each one’s motion would affect its neighbors’ motion. Quantum Pendulum Insights On one hand, the system obeyed Newton’s laws of motion, which govern the physics of our everyday lives, but the precise lengths of the pendula and the connections between them created a magical phenomenon: Newton’s laws caused the wave of the pendulum’s motion to approximately obey Schrödinger’s equation – the fundamental equation of quantum mechanics, which governs the motion of electrons in atoms and in solids. Therefore, the motion of the pendula, which is visible in the macroscopic world, reproduced the behaviors of electrons in periodic systems such as crystals. The researchers pushed a few pendula and then released them. This generated a wave that propagated freely along the chain of pendula, and the researchers could directly measure the evolution of this wave – an impossible mission for the motion of electrons. This enabled the direct measurement of three phenomena. The first phenomenon, known as Bloch oscillations, occurs when electrons within a crystal are influenced by an electric voltage, pulling them in a specific direction. In contrast to what one would expect, the electrons do not simply move along the direction of the field, but they oscillate back and forth due to the periodic structure of the crystal. This phenomenon is predicted to appear in ultra-clean solids, which are very hard to find in nature. In the pendula system, the wave periodically moved back and forth, exactly according to Bloch’s prediction. The second phenomenon that was directly measured in the pendula system is called Zener tunneling. Tunneling is a unique quantum phenomenon, which allows particles to pass through barriers, in contrast to classical intuition. For Zener tunneling, this appears as the splitting of a wave, the two parts of which then move in opposite directions. One part of the wave returns as in Bloch oscillations, while the other part “tunnels” through a forbidden state and proceeds in its propagation. This splitting, and specifically its connection to the motion of the wave in either direction, is a clear characteristic of the Schrödinger equation. In fact, such a phenomenon is what disturbed Schrödinger, and is the main reason for the suggestion of his famous paradox; according to Schrödinger’s equation, the wave of an entire cat can split between a live-cat state and a dead-cat state. The researchers analyzed the pendula motion and extracted the parameters of the dynamics, for instance, the ratio between the amplitudes of the two parts of the split wave, which is equivalent to the quantum Zener tunneling probability. The experimental results showed fantastic agreement with the predictions of Schrödinger’s equation. The pendula system is governed by classical physics. Therefore, it cannot mimic the full richness of quantum systems. For instance, in quantum systems, the measurement can influence the system’s behavior (and cause Schrödinger’s cat to eventually be dead or alive when it is viewed). In the classical system of macroscopic pendulum, there is no counterpart to this phenomenon. However, even with these limitations, the pendula array allows the observation of interesting and non-trivial properties of quantum systems, which may not be directly measured in the latter.

The third phenomenon that was directly observed in the pendula experiment was the wave evolution in a topological medium. Here, the researchers found a way to directly measure the topological characteristic from the wave dynamics in the system – a task that is almost impossible in quantum materials. To this end, the pendula array was tuned twice, so that they would mimic Schrödinger’s equation of the electrons, once in a topological state and once in a trivial (i.e. standard) state. By comparing small differences in the pendulum motion between the two experiments, the researchers could classify the two states. The classification required a very delicate measurement of a difference between the two experiments of exactly half a period of oscillation of a single pendulum after 400 full oscillations that lasted 12 minutes. This small difference was found to be consistent with the theoretical prediction. The experiment opens the door to realizing further situations that are even more interesting and complex, like the effects of noise and impurities, or how energy leakage affects wave dynamics in Schrödinger’s equation. These are effects that can be easily realized and seen in this system, by deliberately perturbing the pendula motion in a controlled manner.

Bye Bye Birdie: How Will Crows Survive Without Us?

Written by AUFTAU on 10 March 2024. Posted in Newsroom.

When the Humans Are Away, Do the Crows Still Play?

A new study from Tel Aviv University examined what happens to birds that are accustomed to living around humans, when their habitat is suddenly emptied of the presence of humans. The study found that when humans are suddenly absent from the urban environment, the activity of the crows and ringneck parakeets that “live” in the area reduces significantly. Conversely, the graceful prinias, who are generally considered shy, increased their activity.

Bird’s Eye View

Among other birds, the researchers tested crows, ringneck parakeets (also known as rose-ringed parakeets) and graceful prinias – and the findings are surprising: while the crows and ringneck parakeets, who are characterized by their tendency to “follow” humans, are already accustomed to the noises they make and feed on their food scraps, decreased their activity, the graceful prinias, which are considered shy, actually increased their activity in the same area. A prinia bird leaninn on a branch. The research was conducted under the leadership of research student Congnan Sun, Dr. Arjan Boonman and Prof. Yossi Yovel, head of The Sagol School of Neuroscience and a member of The School of Zoology at TAU, in collaboration with Prof. Assaf Shwartz from the Landscape Architecture Department at the Technion. The study’s results were published in ELIFE magazine.

Birdemic: A Lockdown Story

As part of the current study, the researchers took advantage of the first COVID-19 lockdown to test the interrelationship between man and nature, and placed 17 recording wide-band sensitive microphones in the Yarkon Park and the streets adjacent to it in northern Tel Aviv. With the help of artificial intelligence, an analysis of the recordings from the first days of the lockdown until 10 days after its end (March 25 to May 28) showed that the activity of the crows and ringneck parakeets was significantly lower (the calls from the crows in the park decreased by about 50% during the lockdowns and the chirping of ringneck parakeets in the park dropped by about 90%). In contrast, the graceful prinias actually benefited from the absence of people and increased their presence by about 12%. Prof. Yossi Yovel explains: “When the first COVID-19 lockdown began, we, like many researchers, in many fields, identified a rare opportunity to conduct field experiments that would examine how animals behave in the absence of humans. In general, many studies indicated the return of species to habitats that humans had ‘abandoned’ because of the coronavirus, but most of these studies were carried out through human observation, which obviously requires humans, who are, as mentioned, the factor whose effect we want to examine. We decided to use microphones to allow us to monitor the activity of birds while humans aren’t present, and to disperse them densely throughout parks and residential neighborhoods. We chose the Yarkon Park area, heading south until Arlozorov Street, and we placed 17 microphones at a distance of about 500 meters away from each other. We chose the ‘old north’ neighborhood of Tel Aviv because it is an urban area adjacent to a park, to enable a comparison between the activity of the birds in a park and the activity of the birds in a city”. Cry of the Crow The researchers examined the changes in the presence of three particularly common and particularly loud bird species, which differ from each other in the extent to which they exploit humans: hooded crow, ringneck parakeet and graceful prinia. The hooded crow is classified as a “human-following species,” that is, it stays near humans and feeds on their food scraps. The ringneck parakeet is an invasive species, it also follows humans. The graceful prinia is classified as “adaptive” – it adapts itself to humans, and knows how to get along in an urban environment, but does not feed on humans’ food scraps and prefers to avoid their company.

In total, the researchers recorded 3,234 hours containing around 250,000 bird calls, using artificial intelligence to identify the calls and the birds that made them. During the lockdown, human activity in the residential areas increased by 49% and human activity in the Yarkon Park – while leaving homes to go to parks was still prohibited – decreased by 31%. “First, we found that the overall activity of the birds, regardless of COVID-19, is 53% higher in the parks than in the streets adjacent to them”, explains Prof. Yuval. “The parks are a center of activity for birds, and that is always true. On the other hand, a complex picture emerges from the lockdown period. The crows and ringneck parakeets, which usually subsist on leftover food from people in the park, searched for other avenues. The calls from the crows in the park decreased by about 50%, and the chirping of the ringneck parakeets in the park dropped by around 90%. Conversely, the shy graceful prinia, an outstanding adaptor, increased its activity by about 12%. These findings highlight the fact that there are animals that depend on us in the city, as well as the flexibility of these animals and the complexity and diversity of the urban ecosystem”.

Revolutionizing Plant Cloning: Boosting Global Agriculture?

Written by AUFTAU on 20 February 2024. Posted in Newsroom.

In an extensive and multi-phased international study that lasted for eight years, led by researchers from the School of Plant Sciences and Food Security at TAU and the Volcani Institute, there were new compounds developed that significantly increased the rooting efficiency of cuttings (typically small branches) taken from mature trees. The researchers explain that getting cuttings to root is a critical component in modern agriculture: “A significant number of fruit trees, as well as forest trees and ornamental plants, are today based on cutting propagation: the creation of plants that are genetic clones of an individual with desirable characteristics. Improving the rooting process can contribute to global agriculture in various aspects: developing new, high-quality varieties, lowering prices for farmers and consumers, increasing the economic viability of new cultivars of crops, and adapting crops to the changing climate conditions”.

Enhancing Nature

The research was led by Dr. Roy Weinstain, research student Ohad Roth from the School of Plant Sciences and Food Security at TAU and Dr. Einat Sadot from the Institute of Plant Sciences at the Volcani Institute. Also participating in the research were Dr. Inna Vints from the TAU School of Plant Sciences and Food Security, Prof. Nir Ben-Tal and Dr. Amit Kessel from the Department of Biochemistry and Molecular Biology at TAU, Sela Yechezkel, Ori Serero, Avi Eliyahu, Pan Tzeela, Dr. Vikas Dwivedi, Dr. Mira Carmeli-Weissberg, Felix Shaya, and Dr. Adi Faigenboim-Doron from the Volcani Institute and Prof. Joseph Riov from the Faculty of Agriculture of the Hebrew University of Jerusalem. The study was in collaboration with researchers from the USA, Germany, Denmark and England and published in the prestigious journal Nature Biotechnology.

Left to right: Dr. Einat Sadot, Dr. Roy Weinstain, Ohad Roth & Sela Yechezkel. Photo credit: The Volcani Institute.

Dr. Sadot explains: “vegetative propagation through cuttings is a method used to propagate plants asexually – not through seeds. In this method, a branch is selected from a plant with desirable properties (e.g. fruit taste, drought resistance, disease resistance, etc.), and parts of that branch, called cuttings or propagules, are exposed to conditions that cause them to grow roots and become independent plants. The new individuals created this way were actually clones with the same genetics as the mother plant. For a crop to be economically viable, rooting percentages of at least 50-60% are necessary, and this figure is a significant consideration for farmers. Rooting percentages vary between different genuses of the same family, between different species of the same genus, and even between different cultivars of the same species, and there are important agricultural plants that are particularly difficult to root”.

Cutting-Edge, Literally

To improve the percentage of plants developing roots, it is necessary to expose cuttings to the plant hormone auxin – a procedure that was discovered more than 70 years ago and has hardly changed since. Dr. Weinstain: “The effectiveness of the existing auxin treatment varies from plant to plant. Numerous agriculturally important plants hardly respond to the standard auxin treatment in terms of root formation that couldn’t be commercialized. In our study, we sought to increase the effect of auxin on the cuttings. Evidence in the scientific literature and observations by experts in the field led us to address the question: will a slow release of the auxin in the plant increase the rooting success of the cuttings?” To do this, the researchers first created a ‘library’ of materials based on synthetic auxin conjugates – molecules in which a synthetic auxin attaches to another chemical group that neutralizes its activity but can be released slowly in plant cells. The library was examined using cuttings from a mature Eucalyptus grandis tree, in which the standard auxin treatment reached low rooting percentages of only 10-15%.

Research student Ohad Roth explains: “The initial examination identified several compounds that have a positive effect on the rooting process, and further research focused on the most effective one. We discovered that this compound enables a combination of high permeability to the plant with a prolonged release of the active substance, the synthetic auxin, so that the auxin stays in the plant much longer, up to a week and a half”. Indeed, the upgraded treatment increased the rooting percentage of the Eucalyptus grandis cuttings to 60% – up to 6 times higher than the rooting percentages found using the standard method.

Later, to more deeply understand the new compound’s mode of action, the researchers used the model plant Arabidopsis thaliana. They discovered that the synthetic auxin used in the new material is more stable (breaks down more slowly) in the plant cells compared to the auxin used in the standard treatment. In addition, the researchers identified a family of enzymes in the plant that are responsible for the release of the synthetic auxin. By modeling these enzymes’ structure and biochemical properties, they have identified important characteristics of their activity.

In the next step, the researchers wanted to see if similar enzymes are also present in other plants – assumingly their presence will allow the new material to be used as well as in other crops. They discovered that this family of enzymes is very ancient and preserved throughout evolution in every tree tested. In light of the encouraging findings, they began to test the effectiveness of the materials they developed on various crops.

Transforming Argan Trees to Agricultural Crops

One of the most meaningful crops examined in the study is the argan – the Moroccan oil tree. The researchers: “The global demand for argan oil is increasing by the years because of its incorporation to a large variety of food, health and skincare products. But to date, the almost exclusive source of this oil is the fruits of argan trees that grow endemically in Morocco and multiply by sexual reproduction, i.e. through seeds. All efforts to turn argan into an agricultural crop, which can be propagated by rooting cuttings, have failed – including attempts here in Israel. In our research, we took cuttings from several argan trees growing in Israel, exposed them to the material we developed, and, this way, succeeded in producing large seedlings from elite selections. In collaboration with the Kibbutzim of Ketura, Beit Kama, Hatzerim and Samar, we planted argan plots based on cuttings from individual specimens, which were rooted using the new rooting material, and we are now examining the possibility of turning them into an agricultural crop”.

The Beautiful Argan Tree

Encouraging results were also observed in experiments with cuttings from apple trees rootstocks, poplar and other varieties of eucalyptus. Higher rooting percentages were achieved in all of them – twice as high or more when compared to the standard auxin treatment. The researchers conclude: “During the research, we developed a material that significantly improves the rooting percentages of cuttings from mature trees. The development could be significant for global agriculture in three aspects:

● Cost reduction: improving the efficacy of the rooting procedure may significantly reduce the cost of procuring seedlings for farmers and, ultimately, the agricultural produce for consumers.

● Improved produce quality: Thanks to the new method, more high-quality cultivars could developed and traded, negating the need to ‘compromise’ on lower-quality varieties simply because they have high rooting rates.

● Environmental compatibility: developing new crop cultivars that adapt to climate change conditions is imperative to sustain agricultural output. The new method can expedite this process and make it more efficient.

In follow-up studies, we plan to deepen the understanding of the new substances’ mechanisms of action and look for additional compounds, perhaps even more effective ones, that can be used as conjugates to slow down the release of auxin in the plant.”

A Scientific Breakthrough That Will Help Increase Plant Yields in Dry Conditions

Written by AUFTAU on 31 January 2024. Posted in Newsroom.

A new discovery by Tel Aviv University has succeeded in cultivating and characterizing tomato varieties with higher water use efficiency without compromising yield. The researchers, employing CRISPR genetic editing technology, were able to grow tomatoes that consume less water while preserving yield, quality, and taste.

The research was conducted in the laboratories of Prof. Shaul Yalovsky and Dr. Nir Sade, and was led by a team of researchers from the School of Plant Sciences and Food Security at Tel Aviv University’s Wise Faculty of Life Sciences. The team included Dr. Mallikarjuna Rao Puli, a former postdoctoral fellow supervised by Prof. Yalovsky, and Purity Muchoki, a doctoral student jointly supervised by Prof. Yalovsky and Dr. Sade. Additional students and postdoctoral fellows from TAU’s School of Plant Sciences and Food Security, along with researchers from Ben Gurion University and the University of Oregon, also contributed to the research. The study’s findings were published in the academic journal PNAS.

The researchers explain that in light of global warming and the diminishing of freshwater resources, there is a growing demand for agricultural crops that consume less water without compromising yield. Naturally, at the same time, because agricultural crops rely on water to grow and develop, it is particularly challenging to identify suitable plant varieties.

In a process called transpiration, plants evaporate water from their leaves. Concurrently, carbon dioxide enters into the leaves, and is assimilated into sugar by photosynthesis, which also takes place in the leaves. These two processes — transpiration and carbon dioxide uptake — occur simultaneously through special openings in the surface of leaves called stomata. The stomata can open and close, serving as a mechanism through which plants regulate their water status.

The researchers highlight that under drought conditions, plants respond by closing their stomata, thereby reducing water loss by transpiration. The problem is that due to the inextricable coupling between the transpiration of the water and the uptake of carbon dioxide, the closing of the stomata leads to a reduction in the uptake of carbon dioxide by the plant. This decrease in carbon dioxide uptake leads to a decline in the production of sugar by photosynthesis. Since plants rely on the sugar generated in photosynthesis as a vital energy source, a reduction in this process adversely affects plant growth.

In crop plants, the decline in photosynthetic sugar production manifests as a decline in both the quantity and quality of the harvest. In tomatoes, for example, the damage to the crop is reflected in a decrease in the number of fruits, their weight, and the amount of sugar in each fruit. Fruits with lower sugar content are less tasty and less nutritious.

In the present study, the researchers induced a modification in the tomato through genetic editing using the CRISPR method, targeting a gene known as ROP9. The ROP proteins function as switches, toggling between an active or inactive state.

Prof. Yalovsky: “We discovered that eliminating ROP9 by the CRISPR technology cause a partial closure of the stomata. This effect is particularly pronounced during midday, when the rate of water loss from the plants in the transpiration process is at its highest. Conversely, in the morning and afternoon, when the transpiration rate is lower, there was no significant difference in the rate of water loss between the control plants and ROP9-modified plants. Because the stomata remained open in the morning and afternoon, the plants were able to uptake enough carbon dioxide, preventing any decline in sugar production by photosynthesis even during the afternoon hours, when the stomata were more closed in the ROP9-modified plants.”

To assess the impact of the impaired ROP9 on the crop, the researchers conducted an extensive field experiment involving hundreds of plants. The results revealed that although the ROP9-modified plants lose less water during the transpiration process, there is no adverse effect on photosynthesis, crop quantity, or quality (the amount of sugar in the fruits). Furthermore, the study identified a new and unexpected mechanism for regulating the opening and closing of the stomata, related to the level of oxidizing substances, known as reactive oxygen species, in the stomata. This discovery holds significant implications for basic scientific knowledge as well.

Dr. Sade: “There is great similarity between the ROP9 in tomatoes and ROP proteins found in other crop plants such as pepper, eggplant and wheat. Therefore, the discoveries detailed in our article could form the basis for the development of additional crop plants with enhanced water use efficiency, and for a deeper understanding of the mechanisms behind stomatal opening and closing.”