It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Saturday, April 08, 2023
Defects can be good and help combat climate change
IMAGE: “DEFECTS TUNE THE STRONG METAL–SUPPORT INTERACTIONS”, A UNIQUE APPROACH TO DESIGN CO2 REDUCTION NANOCATALYST WITH EXCELLENT EFFICIENCY AND STABILITY.view more
CREDIT: MR. RAJESH BELGAMWAR AND PROF. VIVEK POLSHETTIWAR
The heavy use of fossil fuels for driving industrial processes and human activities has resulted in increasingly excessive emissions of anthropogenic CO2 into our atmosphere, surpassing the 400 ppm level. This exceedingly high concentration of atmospheric CO2 has led to a series of negative consequences for our planet’s climate system. However, CO2 can be a strategic carbon resource for synthesizing valued chemicals and fuels. There have been numerous reports of noble metal catalysts, but their application was limited due to their moderate catalytic performance and high cost. In the non-noble metal catalyst family, Cu-based catalysts are among the most versatile, with good potential in many industrial processes. Unfortunately, the low Tammann temperature of copper and the resulting surface migration causes nanoparticles to sinter during the reaction, limiting their activity and long-term stability.
In this work, a Team of researchers led by Prof. Vivek Polshettiwar atTata Institute of Fundamental Research (TIFR), Mumbai, asked the question, how to improve the catalytic activity and stability of Cu-catalyst using the concept of strong metal support interactions (SMSI) and defect sites cooperativity?
They reported a catalyst with active copper sites loaded on titanium oxide-coated dendritic fibrous nanosilica (DFNS/TiO2-Cu) for CO2 to CO conversion. The fibrous morphology and high surface area of DFNS/TiO2 allowed better dispersion and high loading of Cu NPs active sites. This catalyst showed excellent catalytic performance for CO2 reduction with CO productivity of 5350 mmol g−1 h−1 (i.e., 53506 mmol gCu−1 h−1), superior to all copper-based thermal catalysts. Notably, DFNS/TiO2-Cu10 showed 99.8% selectivity towards CO and was stable for at least 200 hours. The defect-controlled strong metal-support interactions between Cu and TiO2 kept the copper nanoparticles firmly anchored on the surface of the support and imparted excellent catalyst stability.
The EELS studies, in-situ diffuse reflectance infrared Fourier transform spectroscopy, H2-temperature-programmed reduction, density functional theory calculations, and long-term stability indicated that there was a strong interaction between copper sites and the Ti3+ sites,which ensured good stability and dispersion of the active copper sites. In-situ studies provided insights into the role of defect sites (Ti3+ and O-vacancies) in tuning SMSI. In-situ time-resolved Fourier transform infrared indicated that CO2 did not directly dissociate to form CO, while the in-situ Raman and in-situ UV-DRS study demonstrated that the intensity of the oxygen vacancies and Ti3+ centers gradually decreased after introducing CO2 gas into the reactor chamber and progressively increased when exposed to hydrogen. This indicated that CO2 to CO conversion followed a redox pathway assisted by hydrogen.
Excellent catalytic performance of DFNS/TiO2-Cu and in-situ mechanistic studies indicated the potential of defects in tuning the strong metal-support interactions. This approach may lead to the design of catalytic systems using various active sites and defective supports.
Defects Tune the Strong Metal–Support Interactions in Copper Supported on Defected Titanium Dioxide Catalysts for CO2 Reduction
Can probiotics cure Florida’s ailing coral reefs? Tests show it works on devastating disease
Coral Reef and Tropical Fish (Shutterstock www.shutterstock.com)
2023/04/07 MIAMI — On a coral reef, white is the color of death.
So when researchers see a flash of bone white amid the riot of colorful corals, fish and sea creatures, they know something is wrong. If it’s all white, the coral likely bleached to death in the steamy hot seas. But if it’s a patch of white surrounded by the raggedy brown edges of living coral tissue, they know the most devastating coral disease in the Caribbean has likely struck.
Stony coral tissue loss disease is a new and deadly disease affecting reefs throughout the Caribbean. Unlike other coral diseases, it affects more than 20 species, and it kills fast — sometimes within a matter of days.
But after nearly a decade of devastating losses, scientists finally have some good news. They have found at least one way to fight back, and they’re already testing it on Florida’s reefs.
A new paper published in the journal Communications Biology found that applying probiotic bacteria — yes, similar to the kind in your yogurt — to corals could prevent the disease, or even reverse some of its symptoms.
“We think about probiotics for our food, but this is probiotics for the reef,” said Julie Meyer, an assistant professor at the University of Florida’s department of soil, water and ecosystem sciences and one of the authors of the study, published Thursday. One healthy coral leads to more
Scientists first discovered the beneficial bacteria a few years back during an experiment where researchers tried to infect healthy corals with the disease to understand how it spread. But one coral just wouldn’t get sick.
Bacteria cultured off of that one coral eventually turned into whole tanks of bacteria, which scientists turned into a paste and started smearing on sick corals. It worked.
Next up were field trials in corals off the coast of Fort Lauderdale and Marathon, in the Keys. Scientists used two methods, sticking the paste on individual corals or dropping a big weighted bag over the colony, pumping in liquid bacterial cultures, and letting the whole thing marinate for a few hours.
Both methods worked, Meyer said, just not as well as they did in the lab.
“In the lab, it’s very effective. In the environment, it’s harder to say because there’s so many variables going on,” she said.
However, scaling up this solution may prove difficult. Florida has hundreds of miles of reef tract, spotted with tens of thousands of sick corals. Tending to each one with a tub of paste, or even the weighted bag, is slow work.
“It’s manpower limitation. It’s a lot of work to go out there and hand-apply this stuff,” she said.
Still, Meyer said her research team is excited at the possibilities shown in this research. For nearly a decade, researchers have been throwing everything they could at these corals — even, she said, essential oils.
So far, the most promising advance has come from antibiotics. Scientists have been successfully using amoxicillin (the same stuff humans get for bacterial infections) to treat sick corals for a few years.
But scientists are worried that using too many antibiotics could create an antibiotic-resistant strain of the disease, and they’re trying to move away from using medicines that humans rely on.
“We don’t want to build that resistance when we need to use it ourselves,” Meyer said. Born in Miami
While much about the disease is still a mystery, scientists are sure of a few things.
They know it was first spotted off Virginia Key in 2014 and quickly raced around the Caribbean. It was devastating. Research from Nova Southeastern University found that at least four species of coral in Florida lost 98% or more of their living tissue to the disease.
Die-off from this disease peaked in Florida around 2016, but it’s still on the move.
In 2021, stony coral tissue loss disease reached the final untouched pocket of Florida: the Dry Tortugas in the Keys. And just this week, scientists recorded a sighting of a sick coral all the way across the Caribbean, in Curacao.
While research hasn’t fingered a specific culprit for the spread of the disease, one of the leading theories is contaminated ballast water from cruise and cargo ships. Miami is the busiest cruise port in the world, and the spread of the disease throughout the Caribbean reflects popular cruising routes.
“When it arrives in a new location it’s around the port areas, and it doesn’t follow ocean currents or anything,” Meyer said.
But so far, no government has asked cruise or cargo ships to alter their behavior to potentially slow the spread of the disease.
And while this new research represents some success in the fight against the spread of stony coral tissue loss disease, researchers said that saving Florida’s beleaguered coral reefs requires hitting all of the problems they’re facing at once, like coral bleaching, ocean acidification and wastewater spills, which are all worsened by climate change.
That’s because each of those factors makes coral weaker and more stressed out, Meyer said, and more susceptible to disease.
“In general, we kind of have to diminish all the stresses on corals in Florida,” she said.
IMAGE: A CLOSE-UP OF EXTENDED POLYPS OF AN APPARENTLY HEALTHY GREAT STAR CORAL COLONY (MONTASTRAEA CAVERNOSA) ON A REEF NEAR FORT LAUDERDALE, FLORIDA. THE TENTACLES SURROUNDING THE MOUTH OF EACH POLYP HELP TRAP FOOD PARTICLES FOR THE CORAL TO EAT. THE BROWN COLORATION IS FROM THE SYMBIOTIC MICROALGAE (SYMBIODINIACEAE) THAT LIVE IN THE CORAL TISSUES. RESEARCHERS WITH THE SMITHSONIAN’S NATIONAL MUSEUM OF NATURAL HISTORY HAVE DISCOVERED THE FIRST EFFECTIVE BACTERIAL PROBIOTIC FOR TREATING AND PREVENTING STONY CORAL TISSUE LOSS DISEASE (SCTLD), A MYSTERIOUS AILMENT THAT HAS DEVASTATED FLORIDA’S CORAL REEFS SINCE 2014 AND IS RAPIDLY SPREADING THROUGHOUT THE CARIBBEAN. THE PROBIOTIC TREATMENT, DESCRIBED IN A PAPER PUBLISHED TODAY IN COMMUNICATIONS BIOLOGY, PROVIDES AN ALTERNATIVE TO THE USE OF THE BROAD-SPECTRUM ANTIBIOTIC AMOXICILLIN, WHICH HAS SO FAR BEEN THE ONLY PROVEN TREATMENT FOR THE DISEASE BUT WHICH RUNS THE RISK OF PROMOTING ANTIBIOTIC-RESISTANT BACTERIA.view more
CREDIT: VALERIE PAUL
Researchers with the Smithsonian’s National Museum of Natural History have discovered the first effective bacterial probiotic for treating and preventing stony coral tissue loss disease (SCTLD), a mysterious ailment that has devastated Florida’s coral reefs since 2014 and is rapidly spreading throughout the Caribbean.
The probiotic treatment, described in a paper published today in Communications Biology, provides an alternative to the use of the broad-spectrum antibiotic amoxicillin, which has so far been the only proven treatment for the disease but which runs the risk of promoting antibiotic-resistant bacteria.
“It just eats the coral tissue away,” said Valerie Paul, head scientist at the Smithsonian Marine Station at Fort Pierce, Florida, and senior author of the study. “The living tissue sloughs off and what is left behind is just a white calcium carbonate skeleton.”
Paul has been studying coral reefs for decades, but she said she decided to go “all in” on SCTLD in 2017 because it was so deadly, so poorly understood and spreading so fast.
While probing how the disease is spread, Paul and a team including researchers from the University of Florida discovered that some fragments of great star coral (Montastraea cavernosa) swiftly developed SCTLD’s characteristic lesions and died, but other pieces never got sick at all.
Though the precise cause of SCTLD is unknown, the efficacy of antibiotics as a treatment suggested pathogenic bacteria were somehow involved in the progression of the disease.
For this reason, the researchers collected samples of the naturally occurring, non-pathogenic bacteria present on a pair of disease-resistant great star coral fragments for further testing. With these samples, the research team aimed to identify what, if any, naturally occurring microorganisms were protecting some great star corals from SCTLD.
First, the team tested the 222 bacterial strains from the disease-resistant corals for antibacterial properties using three strains of harmful bacteria previously isolated from corals infected with SCTLD. Paul and Blake Ushijima, lead author of the study and an assistant professor at the University of North Carolina Wilmington who was formerly a George Burch Fellow at Smithsonian Marine Station, found 83 strains with some antimicrobial activity, but one in particular, McH1-7, stood out.
The team then conducted chemical and genetic analyses to discover the compounds behind McH1-7’s antibiotic properties and the genes behind those compounds’ production. Finally, the researchers tested McH1-7 with live pieces of great star coral. These lab trials provided the final bit of decisive proof: McH1-7 stopped or slowed the progression of the disease in 68.2% of 22 infected coral fragments and even more notably prevented the sickness from spreading in all 12 transmission experiments, something antibiotics are unable to do.
Going forward, Paul said there is a need to work on improved delivery mechanisms if this probiotic is going to be used at scale in the field. Currently, the primary method of applying this coral probiotic is to essentially wrap the coral in a plastic bag to create a mini aquarium and then inject the helpful bacteria. Perhaps even more importantly, Paul said it remains to be seen whether the bacterial strain isolated from the great star coral will have the same curative and prophylactic effects for other species of coral.
The potential of this newly identified probiotic to help Florida’s embattled corals without the danger of inadvertently spawning antibiotic resistant bacteria represents some urgently needed good news, Paul said.
“Between ocean acidification, coral bleaching, pollution and disease there are a lot of ways to kill coral,” Paul said. “We need to do everything we can to help them so they don’t disappear.”
This interdisciplinary research is part of the museum’s new Ocean Science Center, which aims to consolidate museum’s marine research expertise and vast collections into a collaborative center to expand understanding of the world’s oceans and enhance their conservation.
This research was supported by funding from the Smithsonian, the Florida Department of Environmental Protection, the National Science Foundation, the National Oceanic and Atmospheric Administration and the National Institutes of Health.
The remaining live tissue on this great star coral colony (Montastraea cavernosa) in Florida is being destroyed by stony coral tissue loss disease (SCTLD). The bright white margin surrounding the dark brown, living coral tissue is where the coral is bleaching and dying due to the disease. SCTLD afflicts at least two dozen species of so-called hard corals, which provide essential habitat for innumerable fishes and marine animals of economic and intrinsic value while also helping to defend coastlines from storm damage. Since its discovery in Florida in 2014, cases of SCTLD have been confirmed in at least 20 countries. The precise cause of the malady remains unknown but once a coral is infected, its colony of polyps can die within weeks. Researchers with the Smithsonian’s National Museum of Natural History have discovered the first effective bacterial probiotic for treating and preventing SCTLD, a mysterious ailment that has devastated Florida’s coral reefs since 2014 and is rapidly spreading throughout the Caribbean.
A close look at a piece of diseased great star coral (Montastraea cavernosa) that is cut and ready for testing and treatment in an aquarium. The white coral skeleton on the left shows where two coral polyps have already died from stony coral tissue loss disease (SCLTD). Researchers with the Smithsonian’s National Museum of Natural History have discovered the first effective bacterial probiotic for treating and preventing SCTLD, a mysterious ailment that has devastated Florida’s coral reefs since 2014 and is rapidly spreading throughout the Caribbean. While probing how the disease is spread, the research team discovered that some fragments of great star coral swiftly developed SCTLD’s characteristic lesions and died, but other pieces never got sick at all. Though the precise cause of SCTLD is unknown, the efficacy of antibiotics as a treatment suggested pathogenic bacteria were somehow involved in the progression of the disease. For this reason, the researchers collected samples of the naturally occurring, non-pathogenic bacteria present on a pair of disease-resistant great star coral fragments for testing. With these samples, the research team aimed to identify what, if any, naturally occurring microorganisms were protecting some great star corals from SCTLD.
A toolkit for environmentally friendly and cost-effective coral restoration could accelerate the recovery of degraded reefs along the coast of Saudi Arabia and beyond.
Coral reefs support around 30 percent of marine wildlife and provide invaluable ecosystem services, such as fishing, tourism and coastal protection. But these vital habitats are rapidly disappearing.
Despite international climate agreements to reduce carbon emissions and limit global warming, scientists fear that coral reefs have passed a tipping point and will continue declining even under the most optimistic climate scenarios. “We have lost roughly one-third of global coral cover in the last 50 years,” says marine scientist Sebastian Schmidt-Roach, “and we urgently need active measures to mitigate further decline.”
Coral restoration could now be the best line of defense, but progress has been limited by the cost and labor intensity of working in marine environments. Current restoration and coral gardening, or “reefscaping,” projects tend to be small, covering just 500 square meters on average. “We need to target areas of thousands of square kilometers,” says evolutionary biologist Manuel Aranda. “One way to do this is through selective breeding of more resilient corals so that we do not have to restore every reef ourselves, but rather leave some resilient colonies to do the job for us.”
To help achieve industrial-scale coral restoration, the Coral Hub team, including Carlos Duarte and Charlotte Hauser, have created MaritechtureTM – a suite of tools for transporting selectively bred corals from the lab to the reef[1].
The patented system includes tiles that act as a substrate for growing corals: stackable crates to which the tiles can be attached, and MaritechtureTM Reef Nails that will not enable quick attachment of the tiles to natural reef substrates. For reef surfaces where nails won’t work, they created MaritechtureTM Coral Pods – freestanding limestone structures consisting of two plates that interlink to create a four-legged “pod” with a large surface area for attaching tiles or coral fragments.
The researchers calculate that a team of six divers could deploy 90 pods, creating up to 250 square meters of reefscape in half a day. The coral tiles are microchipped so researchers can see what works where and what does not. “Interestingly, our structures have already attracted a lot of natural coral settlement,” adds Schmidt-Roach, a promising sign that these artificial reefs could self-colonize.
Designed in collaboration with artist Julian Charrière, the objects are inspired by the 20th century German Bauhaus style of simple yet functional shapes and rational materials. “Their simple design enables flexibility and low-cost and easy application across different habitats, including in developing nations” says Schmidt-Roach.
“We have tried to minimize the use of plastics and metals. Limestone is a natural reef-like material with significantly less carbon emissions than conventional steel- or cement-based solutions,” Schmidt-Roach explains. Where necessary, the team uses acrylonitrile butadiene styrene, a nontoxic and recyclable plastic that does not degrade in water.
KAUST has announced that MaritechtureTM technologies will provide the backbone of their ambitious Reefscape Restoration Project at Shushah, which Schmidt-Roach’s team initially planned and won funding for. At 100 hectares, this is the world’s largest restoration project to date. MaritechtureTM will soon be commercialized by the team’s start-up Ocean Revive. “We are continually exploring new sustainable materials and nature-based solutions at the interface between science, art and technology,” adds Schmidt-Roach.
Novel infrastructure for coral gardening and reefscaping
Sebastian Schmidt-Roach (left) and Professor Manuel Aranda (right) inspect the health of their sample coralspecimens growing on their patented Maritechture structure.
The different components needed for building the Maritechture structure, including acrylonitrile butadiene styrene, a nontoxic and recyclable plastic that does not degrade in water.
IMAGE: A WHISTLER MALE WITH RADIO TAG ATTACHEDview more
CREDIT: KASTURI SAHA
Just like humans, animals move about to find food, shelter, and mates. Movement in the wild, however, comes with increased risk, as it can be tracked by predators.
To understand how katydids (bushcrickets) are hunted by their predator – the lesser false vampire bat – a group of researchers led by Rohini Balakrishnan, Professor at the Centre for Ecological Sciences (CES), Indian Institute of Science (IISc), fitted tiny radio tags onto these insects and tracked their movement in the canopy. They found that female katydids are at greater risk than males, likely because the former are frequent fliers who cover longer distances.
Published in Behavioral Ecology and Sociobiology, this is the first insect radio tracking study in India, explains Harish Prakash, postdoc at CES and an author of the paper. He says that in addition to field observation, they carried out experiments in a controlled environment to answer key research questions on predator-prey interactions.
Lesser false vampire bats – native to South and Southeast Asia – bring their prey back to their roost to eat. A large proportion of the bat diet consists of insects like katydids. In earlier studies, Balakrishnan and others found that there were a lot more remnants of female wings than males, suggesting that the bats preferred to prey on female katydids. This was unexpected, because katydid females are usually silent, unlike the males that make themselves conspicuous by calling out to attract the females. This led the researchers to ask the question: What about katydid females made them more attractive to the bats?
One possibility is that bats can detect females more easily, since they are usually larger than males. Second, female katydids might be more nutritious than males and therefore preferred by bats. To test these possibilities, the researchers focused on a group of katydids called “whistlers”, in which females are almost double the size and weight of the males. They presented free-flying whistler females as well as males to bats in a large, outdoor cage. Surprisingly, the bats approached both males and females with equal frequency. In fact, in this experimental setup, females escaped capture more often than males. So, it was not the size or nutritive value of the females that increased the risk of their predation.
Then the researchers hit on a third possibility: perhaps the females were flying out more often. To test this, the team glued tiny radio transmitters onto the backs of male and female katydids and tracked them as they flew across trees. What they found was that females tend to move 1.5 times more frequently and 1.8 times farther than males. This led them to conclude that flying more frequently and traveling longer distances across trees may put females at a higher risk of being hunted by bats than males. Kasturi Saha, PhD student at CES and corresponding author on the paper, suggests a possible reason for these frequent long flights: “The females may move around in search of mates, as well as suitable egg-laying sites.”
“In systems where males produce conspicuous acoustic signals and females move silently, it has been assumed that males rather than females perform the higher-risk behaviours,” says Balakrishnan. However, contrary to this view of risk-taking males and risk-averse females, the current study shows that female katydids might be at greater risk of predation.
There are still many unanswered questions about the predator-prey interactions. For example, Saha explains that the bats seem to hunt more female katydids during non-breeding seasons. “This is another mystery we are trying to solve.”
Is flying riskier for female katydids than for males?
How much cadmium is contained in cocoa beans?
A team has developed highly sensitive imaging methods at BESSY II to detect heavy metals such as cadmium in cocoa beans. Improved processing steps could reduce the burden
HELMHOLTZ-ZENTRUM BERLIN FÜR MATERIALIEN UND ENERGIE
IMAGE: COCOA BEANS ARE THE MAIN INGREDIENTS OF CHOCOLATE, A FAMOUS "SOUL FOOD". HOWEVER, COCOA PLANTS ALSO ABSORB TOXIC HEAVY METALS IF THE SOILS ARE POLLUTED. AT BESSY II, A TEAM HAS NOW MAPPED THE LOCAL DISTRIBUTION OF HEAVY METALS INSIDE THE BEANS.view more
CREDIT: HZB
People have been harvesting the beans of the cocoa bush for at least 5000 years. They have learned to ferment, roast, grind and process the beans with sugar and fat to make delicious chocolates. Today, around five million tonnes of beans are on the market every year, coming from only a few growing areas in tropical regions.
Soul food chocolate
Chocolate is considered a soul food: amino acids such as tryptophan brighten the mood. Cocoa beans also contain anti-inflammatory compounds and valuable trace elements. However, cocoa plants also absorb toxic heavy metals if the soils are polluted, for example by mining, which can gradually poison groundwater and soils.
Where do the toxic elements accumulate?
An important question is, where exactly the heavy metals accumulate in the bean, whether rather in the shell or rather in the endosperm inside the bean. From the harvest to the raw material for chocolate, the beans undergo many steps of different treatments, which could possibly reduce the contamination. And ideally the treatment could be optimised in order to make sure that the heavy metals are reduced but the desirable trace elements are retained.
Mapping the beans at BESSY II
A team led by Dr. Ioanna Mantouvalou (HZB) and Dr. Claudia Keil (TU Berlin/Toxicology) has now combined various imaging methods at the BAMline of BESSY II to precisely map the heavy metal concentrations in cocoa beans. They examined cocoa samples from a cultivation region in Colombia, which were contaminated with an average of 4.2 mg/kg cadmium. This is well above the European limits of 0.1-0.8 mg cadmium/kg in cocoa products.
The team worked with three different X-ray fluorescence techniques to examine the cocoa beans. Among other things, they developed a new analytical method for absorption correction when imaging with an X-ray colour camera. "There has been little understanding of how cadmium migrates from the soil through roots into the plant and where the element accumulates in the beans. Especially because it was not possible to precisely localise the cadmium content non-invasively," says Mantouvalou. PhD students Frank Förste (TU Berlin) and Leona Bauer (TU Berlin and HZB) carried out the experiments.
Detecting Cadmium
Cadmium is particularly difficult to detect, explains Mantouvalou. This is because the cadmium signal, which produces the excitation of the outer electrons, lies exactly below the much stronger fluorescence signal of the element potassium, which occurs in higher concentrations in cocoa. "We therefore excite a deeper electron shell of the cadmium atom, which is only possible with hard X-rays at the BAMLine," says Frank Förste. "This enabled us to map the cross-sections of cocoa beans with high resolution, and show that cadmium predominantly accumulates in the outer shell," says Leona Bauer.
Differences before and after roasting
They also discovered interesting differences between beans before and after the roasting process: "We were able to prove that roasting changes the element distribution in the beans," says Mantouvalou. The combination of the different experimental methods allows for the first time to precisely measure the accumulation of cadmium. Further investigations could systematically explore how to improve the processing steps in order to minimise the exposure.
Researchers at the University of Turku, Finland, found that even very low levels of glyphosate-based herbicide residues have a negative effect on endophytic microbes associated with garden strawberry.
In a field study, researchers at the University of Turku, Finland, followed the standard agricultural practices of herbicide application and investigated the impact of glyphosate residues in soil on the endophytic microbial communities of garden strawberry.
Samples collected from strawberry plants that had been growing in the experimental field showed that even though the overall composition of a microbial community and the growth of garden strawberries were unaffected, certain endophytic microbes known for their plant-beneficial functions were relatively less abundant in the strawberry plants that had been exposed to herbicide residues in soil.
“These plant-beneficial microbes are endophytic meaning that they live within leaves and roots of plants. They include bacteria, and fungi, and they form microbial communities within plants. These microbial communities promote nutrition, disease resistance and stress tolerance of their host plants. So, these endophytic microbes are essential partners of plants, as plants depend on them for health and survival,” explains Dr Suni Mathew from the University of Turku Department of Biology.
Glyphosate-based herbicides are used to kill weeds in agricultural fields before sowing and are claimed to degrade quickly in the soil, so that agricultural crops planted after the two-week safety period are not exposed to the chemical. However, other studies have shown that this is not the case and low residues of glyphosate are found in the soil even after two weeks.
In this study, the herbicide plots of experimental field were sprayed with the standard dose of glyphosate-based herbicide (glyphosate concentration: 450 g L–1, CAS: 3864-194-0, application rate: 6.4 L ha−1) and control plots with tap water. After spraying, the researchers observed the two-week long safety period before planting the strawberry plantlets.
Researchers are only starting to understand the importance of endophytic microbes to plant health
The effect of glyphosate is based on inhibition of the ‘shikimate pathway’, a metabolic pathway for the synthesis of amino acids that is found in plants but not in animals. However, this pathway is present also in many microbes.
“It is often overlooked that the shikimate pathway is present in microbes as well. We know already that glyphosate-based herbicides and their residues can affect some free-living microbes in soil. Altogether, we are only starting to understand the importance of endophytic microbes to plant health. Thus, it is important to study whether these microbes are affected by glyphosate residues. The next question is whether the glyphosate residues that imposed changes in endophytic microbes are also affecting plant nutrition, health and disease-resistance, among other things,” says Dr Mathew.
The study also utilised a new bioinformatics approach for finding whether the changes in microbial communities are linked to their sensitivity to glyphosate. The results showed that the microbial community in the roots of the plants in the herbicide plots had more potentially glyphosate-resistant bacteria than the roots of the plants in the control plots. This shift in bacterial community favouring potentially glyphosate-resistant bacteria could cause a decline in microbial diversity.
“Our study shows how even very low residues of agrochemicals can affect plant-associated microbes. Changes in the abundance of certain plant-beneficial endophytic microbes and the dominance of potentially glyphosate resistant bacteria can be concerning if they have consequences on plant health in the long run”, emphasises Dr Mathew.
