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Comment by Dr. Krishna Kumari Challa on April 21, 2023 at 10:50am

Chandra X-ray Observatory identifies new stellar danger to planets

Astronomers using data from NASA's Chandra X-ray Observatory and other telescopes have identified a new threat to life on planets like Earth: a phase during which intense X-rays from exploded stars can affect planets over 100 light-years away. This result has implication for the study of exoplanets and their habitability.

This newly found threat comes from a supernova's blast wave striking dense gas surrounding the exploded star. When this impact occurs it can produce a large dose of X-rays that reaches an Earth-like planet months to years after the explosion and may last for decades. Such intense exposure may trigger an extinction event on the planet.

A new study reporting this threat is based on X-ray observations of 31 supernovae and their aftermath—mostly from NASA's Chandra X-ray Observatory, Swift and NuSTAR missions, and ESA's XMM-Newton—show that planets can be subjected to lethal doses of radiation located as much as about 160 light-years away. Four of the supernovae in the study (SN 1979C, SN 1987A, SN 2010jl, and SN 1994I) are shown in composite images containing Chandra data in the supplemental image.

If a torrent of X-rays sweeps over a nearby planet, the radiation could severely alter the planet's atmospheric chemistry. For an Earth-like planet, this process could wipe out a significant portion of ozone, which ultimately protects life from the dangerous ultraviolet radiation of its host star. It could also lead to the demise of a wide range of organisms, especially marine ones at the foundation of the food chain, leading to an extinction event.

 Ian R. Brunton et al, X-Ray-luminous Supernovae: Threats to Terrestrial Biospheres, The Astrophysical Journal (2023). DOI: 10.3847/1538-4357/acc728

Comment by Dr. Krishna Kumari Challa on April 21, 2023 at 10:32am

How Do Greenhouse Gases Actually Work?

Comment by Dr. Krishna Kumari Challa on April 21, 2023 at 10:16am

Eighteen international experts contributed to the study. Just published in the journal Science, it is the outcome of a virtual scientific workshop held in December 2020, which 62 researchers from 35 countries attended. 

In their study, the experts describe the rapidly worsening loss of species with the aid of sobering figures: they estimate that human activities have altered roughly 75% of the land surface and 66% of the marine waters on our planet. This has occurred to such an extent that today, approximately 80% of the biomass from mammals and 50% of plant biomass has been lost, while more species are in danger of extinction than at any time in human history. In this regard, global warming and the destruction of natural habitats not only lead to biodiversity loss, but also reduce the capacity of organisms, soils and sediments to store carbon, which in turn exacerbates the climate crisis.

Because each organism has a certain tolerance range for changes to its environmental conditions (e.g., temperature), global warming is also causing species' habitats to shift. Mobile species follow their temperature range and migrate toward the poles, to higher elevations (on land, mountain ranges) or to greater depths (in the ocean). Sessile organisms like corals can only shift their habitats very gradually, in the course of generations: as such, they are caught in a temperature trap, which means that large coral reefs could, in the long term, disappear entirely. And mobile species, too, could run into climatic dead ends in the form of mountain summits, the coasts of landmasses and islands, at the poles and in the ocean's depths, if they can no longer find any habitat with suitable temperatures to colonize. In order to address these multiple crises, the researchers propose an ambitious combination of emissions reduction, restoration and protection measures, intelligent land-use management, and promoting cross-institutional competencies among political actors. Needless to say, a massive reduction of greenhouse-gas emissions and reaching the 1.5-degree target continue to be at the top of the priorities list.

 H.-O. Pörtner, Overcoming the coupled climate and biodiversity crises and their societal impacts, Science (2023). DOI: 10.1126/science.abl4881. www.science.org/doi/10.1126/science.abl4881

Part 2

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Comment by Dr. Krishna Kumari Challa on April 21, 2023 at 10:14am

The climate crisis and biodiversity crisis can't be approached separately, says study

Human beings have massively changed the Earth system. Greenhouse-gas emissions produced by human activities have caused the global mean temperature to rise by more than 1.1°C compared to the preindustrial era. And every year, there are additional emissions of carbon dioxide, methane and other greenhouse gases, currently amounting to more than 55 gigatons of carbon dioxide equivalent.

This unprecedented climate crisis has consequences for the entire planet—the distribution of precipitation is shifting, global sea level is rising, extreme weather events are becoming more frequent, the ocean is becoming more acidic, and anoxic zones continue to expand.

The climate crisis they themselves caused is likely the greatest challenge that homo sapiens have faced in their 300,000-year history. 

Yet at the same time another, equally dangerous crisis is unfolding, one that is often overlooked—the dramatic loss of plant and animal species across the planet. The two catastrophes—the climate crisis and biodiversity crisis—are interdependent and mutually amplifying, which is why they should never be seen as two separate things. Consequently, a new review study shows in detail the connections between the climate crisis and biodiversity crisis and presents solutions for addressing both catastrophes and mitigating their social impacts, which are already dramatic.

Part 1

Comment by Dr. Krishna Kumari Challa on April 21, 2023 at 10:01am

In this study, Prof. Ishikawa and his colleagues took a stool sample and multiple blood samples from 96 healthy participants living in Okinawa, starting before the first dose of the vaccine, and ending a month after the second dose.

They then did a broad analysis, looking at all the genes from immune cells in the blood and bacteria in the gut to see if there was any association with an individual's T-cell and antibody levels.

The researchers did not find a significant link to antibody levels, but they did find that individuals that had a lower T-cell response also had a gut microbiome with a high activity of fucose digestion.

The team also found that individuals with a reduced T-cell response had higher expression of two genes, FOS and ATF3, prior to vaccination. These genes are expressed by blood immune cells, and code for proteins that are part of a larger group, called AP-1 transcription factors. Previous research has shown that different AP-1 transcription factors control T-cell survival and activity, but the exact role and function of these two proteins remains unknown.

Individuals with higher expression of FOS and ATF3 prior to vaccination also had microbiomes with high activity of fucose digestion, suggesting that the gut's impact on the immune system is through a pathway that involves FOS and ATF3.

"The mechanism is not yet proven, but we propose that fucose digestion leads to increased baseline expression of FOS and ATF3 in blood immune cells, which in turn weakens the response to the COVID-19 vaccine," said Masato Hirota, first author and Ph.D. student in the Immune Signal Unit. "It's clear that the gut bacteria have an important impact on the overall health of the immune system."

Part 2

Comment by Dr. Krishna Kumari Challa on April 21, 2023 at 10:01am

Gut bacteria could be behind weaker immune responses to COVID-19 vaccine

Gut bacteria that break down a sugar called fucose could be dampening our immune response to the COVID-19 mRNA vaccine, according to a study  by researchers.

The scientists report that increased fucose digestion by bacteria in the gut before vaccination was associated with lower numbers of T-cells activated by vaccination. T-cells are an important type of blood immune cell that are activated by a specific strain of bacteria or virus, and then multiply to fight the infection.

The findings, published April 20 in Communications Biology, illustrate the important impact that the trillions of bacteria in our gut—collectively called our 'gut microbiome'— have on our immune health and adds a missing piece to the puzzle of why vaccination varies in effectiveness from person to person.

While this research focused on the response to the COVID-19 Pfizer mRNA vaccine, the researchers think their results could also be relevant for other mRNA vaccines in development that protect against other infectious diseases, and even cancer.

The researchers now plans to experimentally manipulate the gut bacteria in mice and investigate the exact mechanism of FOS and ATF3, to further understand the link between the microbiome, blood immune cells and the overall immune response.

Human immune and gut microbial parameters associated with inter-individual variations in COVID-19 mRNA vaccine-induced immunity, Communications Biology (2023). DOI: 10.1038/s42003-023-04755-9

Part 1

Comment by Dr. Krishna Kumari Challa on April 21, 2023 at 9:55am

The researchers used charged polymethylmethacrylate particles with different diameters (large and small) to carry out the experiment. A low-polar solvent, cyclohexyl bromide, was used as a dispersing agent.

As the researchers point out, although in both granular (e.g., nut) and colloidal mixtures the "Brazil nut effect" occurs, the mechanisms for its formation are completely different. In the case of a nut mixture, as a result of shaking, smaller nuts fill in the gaps created at the bottom, pushing the larger nuts to the top.

Meanwhile, the charged particles in the colloid make Brownian motion as a result of collisions with the surrounding solvent molecules. "Each particle is positively charged. Heavier but larger particles have a greater charge, so they repel each other more strongly, making them move upward more easily than smaller but lighter particles

The discovery of the "Brazil nut effect" in mixtures of colloidal particles can be used in many fields from geology to soft matter physics. It can also find application in industry such as in the stability of paint and ink.

 Marjolein N. van der Linden et al, Realization of the Brazil-nut effect in charged colloids without external driving, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2213044120

Part 2

Comment by Dr. Krishna Kumari Challa on April 21, 2023 at 9:54am

Defying gravity with the Brazil nut effect

Physicists  have observed—for the first time experimentally—the Brazil nut effect in a mixture of charged colloidal particles.

Until now, it was thought that an influx of external energy was required to create this effect—but the researchers were able to confirm that the process can occur spontaneously. 

Shake an open bag of mixed nuts. Have you noticed that after such a procedure, the largest nuts in the mixture—Brazil nuts—float to the top? The phenomenon of large objects rising to the surface of a mixture of small objects, bearing the professional name of granular convection, is popularly referred to "the Brazil nut effect" and occurs commonly in nature. It can also be observed by shaking, for example, a bucket of sand and pebbles.

This unusual effect contradicts the intuition that heavier objects should sink to the bottom due to gravity and inertia force. This is the case with the phenomenon of sedimentation, common in nature, a process involving the sinking of solid particles dispersed in a liquid, under the influence of gravity or inertia forces. Sedimentation plays a role in processes such as the formation of sedimentary rocks, and is also used to purify water and wastewater or isolate cells from blood.

Until now, it was thought that an influx of external energy, such as shaking the bag, was necessary to create the Brazil nut effect. However, theoretical models being developed suggested that the phenomenon could occur spontaneously, without the supply of external energy. The theoretical calculations were confirmed experimentally for the first time by a group of experimental and theoretical physicists.

They  have shown that the Brazil nut effect can take place in a mixture of charged colloidal particles driven solely by Brownian motions and repulsion of electric charges. 

Part 1

Comment by Dr. Krishna Kumari Challa on April 21, 2023 at 8:29am

Scientists uncover the structure of a bacterial toxin which injects itself into human cells and kills them

researchers have revealed the molecular structure of a cell-killing toxin produced by the bacterium Serratia marcescens.

S. marcescens is commonly involved in hospital-acquired infections – including respiratory diseases, bloodstream and urinary tract infections – and has developed resistance to many commonly used antibiotics.

Researchers discovered the toxin is able to inject itself into and kill a wide range of living cells, including in humans and livestock, insects, and plants.

The team determined the three-dimensional structure of Ssp using X-ray crystallography and identified a specific domain that promotes cell entry. It might also break down protein targets within the cell to cause its death – though more research is needed to confirm this.

The finding, published in Nature Communications, could lead to the development of new antimicrobial treatments and circumvent the use of antibiotics.

By understanding what Ssp looks like scientists can now develop targeted inhibitors.

These inhibitors or antimicrobials may be developed to bind to the part of Ssp responsible for injecting itself into cells.

https://www.nature.com/articles/s41467-023-36719-2

New inhibitors of the Ssp toxin, could be used to ‘disarm’ S. marcescens and reduce the sickness during infections. This would circumvent the use of antibiotics.

https://www.latrobe.edu.au/news/articles/2023/release/new-cell-kill...

Comment by Dr. Krishna Kumari Challa on April 20, 2023 at 1:03pm

Yeast gains power to harness light

The first light-powered brewer’s yeast (Saccharomyces cerevisiae) has been engineered. “It is extraordinary,” says biologist Felipe Santiago-Tirado. “To some extent, it’s like turning an animal into a plant.” A protein called rhodopsin was artificially inserted into yeast cells, giving the fungus the ability to use light as an energy source for some of its cellular functions. Under green light, light-powered yeast cells reproduce fast enough to outgrow normal yeast.

https://www.biorxiv.org/content/10.1101/2022.12.06.519405v2

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