Researchers develop a detector for continuously monitoring toxic gases

The material could be made as a thin coating to analyze air quality in industrial or home settings over time.

MASSACHUSETTS INSTITUTE OF TECHNOLOGY

 

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RESEARCHERS AT MIT HAVE DEVELOPED A DETECTOR THAT COULD PROVIDE CONTINUOUS MONITORING FOR THE PRESENCE OF TOXIC GASES, AT LOW COST. THE TEAM USED A MATERIAL CALLED A METAL-ORGANIC FRAMEWORK, OR MOF (PICTURED AS THE BLACK LATTICE), WHICH IS HIGHLY SENSITIVE TO TINY TRACES OF GAS BUT WHOSE PERFORMANCE QUICKLY DEGRADES. 

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CREDIT: ARISTIDE GUMYUSENGE ET AL

Most systems used to detect toxic gases in industrial or domestic settings can be used only once, or at best a few times. Now, researchers at MIT have developed a detector that could provide continuous monitoring for the presence of these gases, at low cost.

The new system combines two existing technologies, bringing them together in a way that preserves the advantages of each while avoiding their limitations. The team used a material called a metal-organic framework, or MOF, which is highly sensitive to tiny traces of gas but whose performance quickly degrades, and combined it with a polymer material that is highly durable and easier to process, but much less sensitive. 

The results are reported today in the journal Advanced Materials, in a paper by MIT professors Aristide Gumyusenge, Mircea Dinca, Heather Kulik, and Jesus del Alamo, graduate student Heejung Roh, and postdocs Dong-Ha Kim, Yeongsu Cho, and Young-Moo Jo.

Highly porous and with large surface areas, MOFs come in a variety of compositions. Some can be insulators, but the ones used for this work are highly electrically conductive. With their sponge-like form, they are effective at capturing molecules of various gases, and the sizes of their pores can be tailored to make them selective for particular kinds of gases. “If you are using them as a sensor, you can recognize if the gas is there if it has an effect on the resistivity of the MOF,” says Gumyusenge, the paper’s senior author and the Merton C. Flemings Career Development Assistant Professor of Materials Science and Engineering.

The drawback for these materials’ use as detectors for gases is that they readily become saturated, and then can no longer detect and quantify new inputs. “That’s not what you want. You want to be able to detect and reuse,” Gumyusenge says. “So, we decided to use a polymer composite to achieve this reversibility.”

The team used a class of conductive polymers that Gumyusenge and his co-workers had previously showncan respond to gases without permanently binding to them. “The polymer, even though it doesn’t have the high surface area that the MOFs do, will at least provide this recognize-and-release type of phenomenon,” he says.

The team combined the polymers in a liquid solution along with the MOF material in powdered form, and deposited the mixture on a substrate, where they dry into a uniform, thin coating. By combining the polymer, with its quick detection capability, and the more sensitive MOFs, in a one-to-one ratio, he says, “suddenly we get a sensor that has both the high sensitivity we get from the MOF and the reversibility that is enabled by the presence of the polymer.”

The material changes its electrical resistance when molecules of the gas are temporarily trapped in the material. These changes in resistance can be continuously monitored by simply attaching an ohmmeter to track the resistance over time. Gumyusenge and his students demonstrated the composite material’s ability to detect nitrogen dioxide, a toxic gas produced by many kinds of combustion, in a small lab-scale device. After 100 cycles of detection, the material was still maintaining its baseline performance within a margin of about 5 to 10 percent, demonstrating its long-term use potential.

In addition, this material has far greater sensitivity than most presently used detectors for nitrogen dioxide, the team reports. This gas is often detected after the use of stove ovens. And, with this gas recently linked to many asthma cases in the U.S., reliable detection in low concentrations is important. The team demonstrated that this new composite could detect, reversibly, the gas at concentrations as low as 2 parts per million. 

While their demonstration was specifically aimed at nitrogen dioxide, Gumyusenge says, “we can definitely tailor the chemistry to target other volatile molecules,” as long as they are small polar analytes, “which tend to be most of the toxic gases.”

Besides being compatible with a simple hand-held detector or a smoke-alarm type of device, one advantage of the material is that the polymer allows it to be deposited as an extremely thin uniform film, unlike regular MOFs, which are generally in an inefficient powder form. Because the films are so thin, there is little material needed and production material costs could be low; the processing methods could be typical of those used for industrial coating processes. “So, maybe the limiting factor will be scaling up the synthesis of the polymers, which we’ve been synthesizing in small amounts,” Gumyusenge says.

“The next steps will be to evaluate these in real-life settings,” he says. For example, the material could be applied as a coating on chimneys or exhaust pipes to continuously monitor gases through readings from an attached resistance monitoring device. In such settings, he says, “we need tests to check if we truly differentiate it from other potential contaminants that we might have overlooked in the lab setting. Let’s put the sensors out in real-world scenarios and see how they do.”

The work was supported by the MIT Climate and Sustainability Consortium (MCSC), the Abdul Latif Jameel Water and Food Systems Lab (J-WAFS) at MIT, and the U.S. Department of Energy.

 

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Written by David L. Chandler, MIT News

Paper: “Robust chemiresistive behavior in conductive polymer/MOF composites”

https://doi.org/10.1002/adma.202312382

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JOURNAL

Advanced Materials

DOI

10.1002/adma.202312382 

ARTICLE TITLE

Robust Chemiresistive Behavior in Conductive Polymer/MOF Composites

 UK

WORD OF THE DAY

SIR Keir Starmer’s reputation as “Mr Rules” reflects the growing “juridifcation” of politics, study shows

UNIVERSITY OF EXETER

Keir Starmer’s efforts to be “Mr Rules” and his focus on calling for inquiries reflects the growing “juridification” of politics, experts have said.

    

Though the Labour leader’s consistent      calls for probes into the conduct of government, often culminating in demands for resignations, could be seen as a mere      tactic of opposition politics, the study argues that it is      symptomatic of the “juridification” of politics - the ceding of the terrain of politics to the seemingly superior and separate domains of law and administration.

 

This  marks the abandonment of values-based politics in favour of a reliance upon rules, norms, conventions and procedures to address substantive matters of public policy.

 

The study, by Dr Jamie Johnson, from the University of Leicester, Dr Owen Thomas, from the University of Exeter and Professor Victoria Basham, from Cardiff University, is published in the journal British Politics.

    

Dr Thomas said: “Through this rules-based, rather than values-based approach to politics, the task of government is reduced to the dual imperatives of maintaining standards of probity and competency in public office. Such an approach to politics tends to focus more on restoring established forms of conduct rather than seeking forms of political renewal or reimagination.

 

“As the contours of an incoming Labour government begin to emerge, it is unclear whether such an approach to politics can meaningfully respond to the series of reinforcing crises it will be tasked with tackling: from the climate emergency to the cost of living. The challenge for Labour is to make sense of a political moment in which problems arise as much from the following of established rules as their transgression.”

 

The study says a persistent feature of Labour’s opposition to policies such as immigration and asylum is that it appears more comfortable talking about efficacy than ethics, processes not principles.

 

At times, Labour is keen to appear as the reluctant inheritor and administrator of Conservative policy. At other times, however, Labour appears keen to emphasise elements of continuity as a sign of their seriousness, pragmatism, and readiness for government.

 

Professor           Basham      commented: “Our argument is that Starmer’s ‘forensic’ style, with its associated emphasis on probity and competency, should be read as a continuation of a global trend in the juridification of politics, that signifies a reliance on judicial and quasi-judicial means to address substantive ethical and political matters of public policy.

 

“It is an approach to politics which stands back and lets the law, the rule, the procedure decide. It is unpolitical in that it seeks to stand above the political sphere and to seek political outcomes by means other than politics. It does so through the conspicuous abandonment of the terrain of politics and the reification of the seemingly superior and separate spheres of law and administration.”

 

“This rise of juridification has not gone unnoticed. The Conservative government clearly understands that the most concerted and effective opposition to their policies in recent years has come through law, not politics. In response, Conservative rhetoric has been defined by attacks against the institutions that administer ‘the rules’: human rights lawyers, supreme court and European judges, civil servants, Treasury orthodoxy, and the so-called ‘left-wing economic establishment’.”

 

Dr Johnson said: “The juridification of politics extends well beyond Starmer’s Labour Party, capturing a broader trend within centre and centre-left politics in which progressive political outcomes are increasingly sought with recourse to the law. The juridification of politics is not simply to pursue good politics through good law, it is to reduce and equate good politics to good law.

    

“If politics is to be nothing more than ensuring adherence to the rules and policing their transgression, then what are we left with in an age in which the rules themselves appear to be the problem?”

 

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JOURNAL

British Politics

DOI

10.1057/s41293-024-00258-1 

METHOD OF RESEARCH

Meta-analysis

SUBJECT OF RESEARCH

People

ARTICLE TITLE

‘Mr Rules’: Keir Starmer and the juridification of politics.

ARTICLE PUBLICATION DATE

16-May-2024

Natural toxins in food: Many people are not aware of the health risks

German Federal Institute for Risk Assessment publishes special edition of the BfR Consumer Monitor

BFR FEDERAL INSTITUTE FOR RISK ASSESSMENT

Many people are concerned about residues of chemicals, contaminants or microplastics in their food. However, it is less well known that many foods also contain toxins of completely natural origin. These are often chemical compounds that plants use to ward off predators such as insects or microorganisms. These substances are found in beans and potatoes, for example, and can pose potential health risks. However, according to a recent representative survey by the German Federal Institute for Risk Assessment (BfR), only just under half of the respondents (47 per cent) were even aware of plant toxic substances. The BfR Consumer Monitor Special on naturally occurring plant toxins also revealed that this risk worries 27 per cent. In contrast, residues in food (e.g. from plant protection products) and contaminants, i.e. substances that are not intentionally added to food (e.g. heavy metals), cause concern for 63 and 62 per cent of respondents respectively. "The survey results make it clear that risks of natural origin tend to be underestimated, while risks of synthetic origin tend to be overestimated," says BfR President Professor Andreas Hensel."

Link to the consumer monitor

https://www.bfr.bund.de/cm/364/bfr-consumer-monitor-2024-special-naturally-occurring-plant-based-toxins.pdf

Raw plant-based foods are consumed frequently by 34 per cent, occasionally or rarely by 45 per cent and very rarely or not at all by 19 per cent.

Which foods with naturally occurring plant toxins do you already know? If this question is asked openly and without pre-selection, potatoes are named first (15 per cent), followed by tomatoes, raw beans (nine per cent each) and mushrooms (five per cent).

Naturally occurring toxic substances worry 27 per cent in the survey. More than half of the respondents (53 per cent) feel poorly informed about plant toxins in food, while only eight per cent feel well informed.

At 63 per cent and 62 per cent respectively, significantly more consumers are concerned about residues or contaminants.

Residues are residual amounts of substances that are used in the production of food. For example, residues can remain in fruit, vegetables or cereals even if plant protection products are used correctly.

Contaminants, on the other hand, are undesirable substances that unintentionally end up in food. They can occur naturally in the environment, arise during the processing of raw materials into food or be released into the environment as a result of human activities. Contaminants are undesirable because they can be harmful to health under certain circumstances.

The study also shed light on the related topic of "mouldy food". Here, too, there is a clear need for education. Even small amounts of mould toxins can be harmful to the health of humans and animals. Mouldy jam, for example, should therefore always be disposed of completely. Nevertheless, 25 per cent of respondents stated that they only remove the mouldy part. Even in the case of mouldy berries, affected and surrounding fruit should no longer be eaten. Only 60 per cent adhere to this rule.

 

About the BfR

The German Federal Institute for Risk Assessment (BfR) is a scientifically independent institution within the portfolio of the Federal Ministry of Food and Agriculture (BMEL) in Germany. The BfR advises the Federal Government and the States (‘Laender’) on questions of food, chemicals and product safety. The BfR conducts independent research on topics that are closely linked to its assessment tasks.

This text version is a translation of the original German text which is the only legally binding version.

Fast track to food safety: new test spots seafood pathogen in 30 minutes

ZHEJIANG UNIVERSITY

 

IMAGE: 

SCHEMATIC SHOWING THE USE OF A CRISPR/CAS12A SYSTEM COMBINED WITH ISOTHERMAL AMPLIFICATION AND ICS FOR RAPID AND VISUAL NUCLEIC ACID DETECTION.

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CREDIT: FOOD QUALITY AND SAFETY

Researchers have developed a groundbreaking point-of-care detection method for Vibrio parahaemolyticus, a bacterium responsible for a significant number of foodborne illnesses. The new platform, leveraging recombinant polymerase amplification (RPA) and the CRISPR/Cas12a system combined with an immunochromatographic test strip (ICS), offers a low-cost, simple, and visually intuitive solution for the rapid detection of this pathogen in seafood.

Vibrio parahaemolyticus is a Gram-negative, halophilic bacterium prevalent in marine environments and is the primary cause of acute hepatopancreatic necrosis, also known as early death syndrome, in aquaculture. It represents a considerable public health hazard, especially through the consumption of raw or undercooked seafood. The bacterium can contaminate seafood surfaces, leading to foodborne outbreaks. Current detection methods, which rely on microbial isolation, culturing, and biochemical identification, are too slow for effective point-of-care testing (POCT).

In a notable advancement for food safety, scientists from the Shanghai Academy of Agricultural Sciences have unveiled a novel detection platform that identifies Vibrio parahaemolyticus within 30 minutes. This innovation could significantly reduce the risk of foodborne illness from seafood. Published in Food Quality and Safety, (DOI:10.1093/fqsafe/fyae008) , February 2024, this method marks a substantial improvement in food safety and public health measures.

The research team developed an innovative platform that swiftly detects the presence of Vibrio parahaemolyticus in seafood. This rapid-response system is transformative for food safety, where early detection of pathogens is crucial for preventing illness. The platform utilizes a combined approach involving recombinant polymerase amplification (RPA), the CRISPR/Cas12a system, and an immunochromatographic test strip (ICS). It specifically targets the tlh gene of V. parahaemolyticus, facilitating highly sensitive detection. The procedure starts with extracting bacterial DNA from the seafood sample, followed by RPA for amplification. The CRISPR/Cas12a system then accurately identifies and cleaves the target gene, with the ICS providing a visual confirmation of the bacterium's presence. This method achieves a detection limit of 2.5×102 fg/µL for plasmid DNA and 1.4×102 CFU/mL for the bacteria. Remarkably, it can detect V. parahaemolyticus in salmon sashimi at concentrations as low as 154 CFU/g without sample enrichment. This breakthrough overcomes the drawbacks of traditional culture-based methods, offering a faster, more accessible approach for monitoring seafood safety.

Dr. Haijuan Zeng, the corresponding author and leader of the Biotechnology Research Institute at the Shanghai Academy of Agricultural Sciences, stated, "Our innovative detection platform represents a significant advancement in the rapid and sensitive detection of Vibrio parahaemolyticus, proving especially valuable for ensuring seafood safety and preventing public health crises."

This new method could revolutionize how food safety is monitored in the seafood industry, offering a rapid, cost-effective solution that can be implemented directly at points of sale or during food handling, significantly shortening the detection timeframe and potentially averting foodborne outbreaks before contaminated products reach consumers.

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References

DOI

10.1093/fqsafe/fyae008

Original Source URL

https://doi.org/10.1093/fqsafe/fyae008

Funding information

This study was supported by the Scientific and Innovative Action Plan of Shanghai (No.21N31900800), the Shanghai Rising-Star Program (No.23QB1403500), the Shanghai Science and Technology Commission, the Belt and Road Project (No.20310750500), the Talent Project of SAAS (No.2023–2025), and the SAAS Program for Excellent Research Team (No.2022 (B-16)), China.

About Food Quality and Safety

Food Quality and Safety (FQS) is an open access, international, peer-reviewed journal providing a platform to highlight emerging and innovative science and technology in the agro-food field, publishing up-to-date research in the areas of food quality, food safety, food nutrition and human health. It is covered by SCI-E and the 2022 Impact Factor (IF)=5.6, 5-yr IF=6.2.

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JOURNAL

Food Quality and Safety

DOI

10.1093/fqsafe/fyae008 

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

A visual, rapid, and sensitive detection platform for Vibrio parahaemolyticus based on RPA-CRISPR/Cas12a and an immunochromatographic test strip

 

Charred stable remains from the Punic War period provide a glimpse into life in the Pyrenees in the Iron Age

UNIVERSITAT AUTONOMA DE BARCELONA

A research led by the UAB discovers the remains of six dead animals burned inside a stable in the Pyrenean village of Bellver de Cerdanya 2,200 years ago. Victims of a violent fire that may have been related to the passage of the Carthaginian army, the animals appeared along with some of the inhabitants’ valuables, such as a gold earring. The finding has made it possible to reconstruct the economic patterns of these inhabitants, with an important livestock breeding in which transhumance was practiced.

 

A research at the Tossal de Baltarga archaeological site, in Bellver de Cerdanya (Lleida Pyrenees), has brought to light the charred remains of a building, called Building G by archaeologists, burned by a fire 2,200 years ago, in the Iron Age. The building had two floors and the fire caused the roof, the support beams and the upper wooden floor to collapse.

 

The researchers, led by Oriol Olesti, lecturer of the Department of Antiquity and Middle Age Studies at the UAB, found the charred remains of a horse, four sheep and a goat, along with valuables such as an iron pickaxe and a gold earring concealed in a pot. From what researchers inferred, the upper floor appeared to have been divided into storage and textile production spaces. Numerous tools were found that could have been used for spinning and weaving the wool of the sheep and goats that lived on the lower floor, such as spindle whorls and loom weights. Archaeologists also found cereals such as oats and barley, and cooking vessels, with residues showing that the people using the building had been consuming milk and cheese and eating pork and lamb stews.

 

Findings show a complex economy

 

 

"The discovery has allowed us to reconstruct the economic patterns of these inhabitants, probably dedicated to transhumance", explains Oriol Olesti. The isotope analysis indicates that some sheep had previously grazed in the lowland pastures, possibly by agreement with other communities.

 

"These mountain communities were not closed in the highlands, but connected with neighboring areas, exchanging products and, likely, cultural backgrounds," said Olesti. The complex economy of these settlers, with farming, agriculture, forest management and mining activities, indicates "an Iron Age society adapted to their environment and taking advantage of their resources in the highlands. But it also shows their contact with other communities," he adds.

 

 

The passing of Hannibal's troops

 

The destruction of Tossal de Baltarga, which occupied a strategic position in the Pyrenees, could have been related to the passage of Hannibal's army through this region to fight against the Romans during the Second Punic War. "The chronological precision in archaeology to speak of the Punic War is not enough to affirm this for sure," says Oriol Olesti, "but we are very clear that it happened at that time in history." He goes on to add that: "It is likely that the violent destruction of the site is related to this war. The general fire points to an anthropic destruction, intentional and very effective, since all the buildings on the site were destroyed. In an adjacent building we also found a burned dog."

 

Tossal de Baltarga was a place of residence and lookout point for the Cerretani community with an important fortified settlement nearby, the Castellot de Bolvir. It seems to have lacked defensive walls, but had an excellent view over the river and the main travel routes. "These valleys were an important territory economically and strategically," Olesti remarks. "We know that Hannibal crossed the Pyrenees fighting against local tribes, also probably against the Cerretani. Not many archaeological remains are preserved from this expedition, but Tossal de Baltarga is probably one of the best examples."

 

A hidden gold earring

 

According to Olesti, "our reconstruction implies a sudden destruction, with no time to open the stall and save the animals". "This could just be an unexpected local fire. But the presence of a hidden gold earring indicates the anticipation by the local people of some kind of threat, likely the arrival of an enemy. Also, the keeping of such a high number of animals in a little stall suggests the anticipation of a danger."

 

Archaeologists do not know what became of the inhabitants of Tossal de Baltarga, but it was eventually reoccupied and used by the Romans. A part of the community likely survived the conflagration, and later lived alongside the Romans at the site. The most significant element of this new occupation is the impressive watchtower that remains at the site.

 

The research, published today in Frontiers in Environmental Archaeology, was led by Oriol Olesti, researcher of the UAB Department of Antiquity and Middle Age Studies, with the participation of Jordi Morera, Joan Oller and Jose M. Carrasco, researchers of the same department, as well as by researchers of the UAB Department of Prehistory Anna Berrocal, Oriol López Bultó, Laura Obea, Nadia Tarifa and Joaquim Sisa López de Pablo; Lídia Colominas, from the Catalan Institute of Classical Archaeology (ICAC-CERCA); Marta Portillo, from the Institució Milà i Fontanals of the CSIC; Paula Tàrrega, from the University of Heidelberg; and Chiara Messana, from the Catalan Institute of Human Palaeoecology and Social Evolution (IPHES-CERCA).

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JOURNAL

Frontiers in Environmental Archaeology

DOI

10.3389/fearc.2024.1347394 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

The exploitation of mountain natural resources during the Iron Age in the Eastern Pyrenees: the case study of production unit G at Tossal de Baltarga (Bellver de Cerdanya, Lleida, Spain)

ARTICLE PUBLICATION DATE

17-May-2024

A devastating fire 2,200 years ago preserved a moment of life and war in Iron Age Spain — right down to a single gold earring

A violent blaze, possibly linked to the Carthaginian army crossing the Pyrenees to fight the Romans, flared up so quickly people couldn’t save their animals or their valuables

Peer-Reviewed Publication

FRONTIERS

 

IMAGE: 

BUILDING G AS IT MIGHT HAVE LOOKED BEFORE THE FIRE, INTERPRETED BY FRANCESC RIART, ILLUSTRATOR. 

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CREDIT: RECONSTRUCTION BY FRANCESC RIART, ILLUSTRATOR. SHARED BY KIND PERMISSION OF THE AUTHORS.

A ruined building in the middle of the Pyrenees records a tragedy for the people who lived there — a devastating fire which burned a settlement to the ground, destroying everything down to a hidden gold earring. Now archaeologists’ excavation of Building G, in the strategically placed Iron Age site of Tossal de Baltarga, reveals a way of life derailed by violence: potentially, a forgotten episode of the war between Carthage and Rome.

“The destruction was dated around the end of the third century BCE, the moment where the Pyrenees were involved in the Second Punic War and the passage of Hannibal’s troops,” said Dr Oriol Olesti Vila of the Autonomous University of Barcelona, lead author of the article in Frontiers in Environmental Archaeology. “It is likely that the violent destruction of the site was connected to this war. The general fire points to anthropic destruction, intentional and very effective — not only Building G, but all the buildings of the site, were destroyed. In Building D we found a complete dog, burned…”

Buried treasure

Tossal de Baltarga was a hillfort of the Cerretani community, who had a major settlement at nearby Castellot de Bolvir. It seems to have lacked defensive walls, but commanded an excellent view over the river and critical travel routes. Its sudden destruction preserved organic remains, which allowed archaeologists to paint a detailed picture of the life that its occupants lived until it was set alight. 

“These valleys were an important territory economically and strategically,” said Olesti Vila. “We know that Hannibal passed the Pyrenees fighting against the local tribes, likely the Cerretani. Not many archaeological remains of this expedition are preserved. Tossal de Baltarga is likely one of the best examples.”

Building G had two floors. The fire burned so fiercely that the roof, support beams, and wooden upper floor fell in, but some of the valuables survived the fall: the archaeologists found an iron pickaxe and the gold earring, concealed in a little pot. 

This upper floor seems to have been divided into spaces for cooking and textile production. Numerous spindle whorls and loom weights were found, which could have been used to spin and weave wool from the sheep and goat that lived on the lower floor. Archaeologists also found edible grains like oats and barley, and some cooking vessels, with residues that showed the people who used Building G had been drinking milk and eating pork stews. 

A memory of conflict

While no human remains were found in Building G, six animals did not escape. The four sheep, goat, and horse — which may have been ridden by the owners of Building G; it was old enough and a metal horse bit was found — were penned up in their wooden enclosures with their feed. They could even have been trapped by a closed door, which would explain burned wood found in the entrance. This penning might have been a departure from usual practices, caused by the fear of conflict: isotope analysis indicates some sheep had previously grazed in lowland pastures, possibly by arrangement with other communities. 

“These mountain communities were not closed in the highlands, but connected with neighboring areas, exchanging products and, likely, cultural backgrounds,” said Olesti Vila. “The complex economy indicates an Iron Age society adapted to their environment and taking advantage of their resources in the highlands. But it also shows their contact with other communities.” 

“Our reconstruction implies a sudden destruction, with no time to open the door of the stall and save the animals,” added Olesti Vila. “This could be just an unexpected local fire.  But the presence of a hidden gold earring indicates the anticipation by the local people of some kind of threat, likely the arrival of an enemy. Also, the keeping of such a high number of animals in a little stall suggests the anticipation of a danger.”

Archaeologists don’t know what became of the people who were living at Tossal de Baltarga, but it was eventually reoccupied, and garrisoned by the Romans. Some part of the community likely survived the conflagration. Perhaps remembering the burning of Building G and its neighbors, these later occupants of Tossal de Baltarga constructed defenses — including an impressive watchtower. 

The gold earring found by the scientists, photographed against a dark background, in front of the jar it was found in.

CREDIT

Marco Ansalon

JOURNAL

Frontiers in Environmental Archaeology

DOI

10.3389/fearc.2024.1347394 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

The exploitation of mountain natural resources during the Iron Age in the Eastern Pyrenees: the case study of production unit G at Tossal de Baltarga (Bellver de Cerdanya, Lleida, Spain)

ARTICLE PUBLICATION DATE

17-May-2024

 

Zombie cells in the sea: Viruses keep the most common marine bacteria in check

MAX PLANCK INSTITUTE FOR MARINE MICROBIOLOGY

 

IMAGE: 

SUNSET OVER THE ISLAND OF HELGOLAND IN THE GERMAN BIGHT, WHERE THE RESEARCHERS FROM THE MAX PLANCK INSTITUTE FOR MARINE MICROBIOLOGY OBTAINED THEIR SAMPLES.

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CREDIT: JAN BRÜWER/MAX PLANCK INSTITUTE FOR MARINE MICROBIOLOGY

The ocean waters surrounding the German island of Helgoland provide an ideal setting to study spring algae blooms, a focus of research at the Max Planck Institute for Marine Microbiology since 2009. In a previous study, the Max Planck scientists observed a group of bacteria called SAR11 to grow particularly fast during these blooms. However, despite their high growth rates, the abundance of SAR11 decreased by roughly 90% over five days. This suggested that the cells were quickly decimated by predators and/or viral infections. Now, the Max Planck researchers investigated what exactly lies behind this phenomenon.

Finding the phages infecting SAR11

“We wanted to find out if the low numbers of SAR11 were caused by phages, that is viruses that specifically infect bacteria”, explains Jan Brüwer, who conducted the study as part of his doctoral thesis. “Answering this seemingly simple question was methodologically very challenging”.

How does phage infection work? Phages infect bacteria by introducing their genetic material into them. Once there, it replicates, and utilizes the bacterial ribosomes to produce the proteins it needs. Researchers from Bremen used a technology that enabled them to “follow” the phage’s genetic material inside the cell. “We can stain the specific phage genes and then see them under the microscope. Since we can also stain the genetic material of SAR11, we can simultaneously detect phage-infected SAR11 cells”, explains Jan Brüwer.

While this might seem straightforward, the low brightness and small size of the phage genes made it challenging for researches to detect them. Nonetheless, thousands of microscope images were successfully analyzed, bringing some exciting news.  

“We saw that SAR11 bacteria are under massive attack by phages”, says Jan Brüwer. “During periods of rapid growth, such as those associated with spring algae blooms, nearly 20% of the cells were infected, which explains the low cell numbers. So, phages are the missing link explaining this mystery.”

Zombie cells: A global phenomenon

To the surprise of the scientists, the images revealed even more. "We discovered that some of the phage-infected SAR11 cells no longer contained ribosomes. These cells are probably in a transitional state between life and death, thus we called them 'zombie' cells”, Brüwer explains.

Zombie cells represent a novel phenomenon observed not only in pure SAR11 cultures but also in samples collected off Helgoland. Furthermore, analysis of samples from the Atlantic, Southern Ocean, and Pacific Ocean revealed the presence of zombie cells, indicating this phenomenon occurs worldwide.

“In our study, zombie cells make up to 10% of all cells in the sea. The global occurrence of zombie cells broadens our understanding of the viral infection cycle”, Brüwer emphasizes. “We suspect that in zombie cells, the nucleic acids contained in the ribosomes are being broken down and recycled to make new phage DNA.”

Brüwer and his colleagues hypothesize that not only SAR11 bacteria, but also other bacteria, can be turned into zombies. Thus, they want to further investigate the distribution of zombie cells and their role in the viral infection cycle.

“This new finding proves that the SAR11 population, despite dividing so fast, is massively controlled and regulated by phages”, stresses Brüwer. “SAR11 is very important for global biogeochemical cycles, including the carbon cycle, therefore their role in the ocean must be redefined. Our work highlights the role of phages in the marine ecosystem and the importance of microbial interactions in the ocean”.

Infected cells and zombie cells 

Under the microscope, scientists identified SAR11 zombie cells by their distinct lack of ribosomes. In an example comparing a live, infected SAR11 cell to an infected zombie cell: blue indicates bacterial DNA, yellow shows ribosomes, and purple highlights phage genes. The live cell (upper pictures) displays all three colors, while the zombie cell (lower pictures) lacks the yellow ribosome signal. The final column of images on the right merges these colors, clearly distinguishing the two cell types.

CREDIT

Jan Brüwer/Max Planck Institute for Marine Microbiology

JOURNAL

Nature Communications

DOI

10.1038/s41467-024-48172-w 

ARTICLE TITLE

Globally occurring pelagiphage infections create ribosome-deprived cells

LA REVUE GAUCHE - Left Comment: Search results for BACTERIOPHAGE