by CHRISTIAN COTRONEO

Peeling a banana doesn’t require the nimblest of fingers. It’s basically Nature’s version of a twist-off bottle cap. Anyone with any kind of digits can get to the tasty slip of sweetness inside. But what if even that was too much of a bother? Why not just chomp right through the skin and be done with it?

Well, some experts suggest you can do just that. As Australian dietitian Susie Burrell notes on her blog, eating the whole banana may go a long towards reducing food waste and upping your nutritional intake.

“You will increase your overall fibre content by at least 10 percent as a lot of dietary fibre can be found in the skin of the banana,” she writes. “You will get almost 20 percent more Vitamin B6 and almost 20 percent more Vitamin C and you will boost both your potassium and magnesium intake.”

But the real question is, would you like to bite into a whole banana? Or does the idea of eating a banana peel sound more like an insult you might sling at someone? Maybe you’re face is all puckered up right now at the very thought of it.

There’s an important caveat. Burrell, mercifully, doesn’t advise hunkering down on the whole banana. Instead, you’re going to want to remove that skin and cook it on its own — breaking down the tough cellular walls and making those nutrients more readily absorb-able (and the whole affair, perhaps a little less gag-able.)

Burrell is hardly alone in endorsing whole-banana consumption. As the site Treehugger points out, Americans devour 12 billion bananas per year. That’s 12 billion banana peels needless discarded — and maybe even 12 billion opportunities someone will slip and have a terrible accident.

It also represents a lot of nutrients and other potential benefits being chucked to the curb. According to a study published in the Journal of Immunology Research by scientists at Seoul National University, a typical yellow peel packs substantial amounts of potassium, dietary fiber, polyunsaturated fats and essential amino acids.

Those nutrients do a lot of good for a body — particularly all that potassium, which can regulate blood pressure and keep hearts and kidneys healthy.

Sure, there’s plenty of potassium already in nature’s sweetest candy — about 422 milligrams in the average serving. But with an added 78 milligrams of the stuff — along with so many other nutrients — why not eat the wrapper too?

Well, aside from a banana peel needing a little preparation to be fully digestible, there are also those agricultural ne’er-do-wells known as pesticides. The outer layers of fruits and vegetables tend to stockpile somewhat worrisome levels of pesticide residue, although federal bodies like the United States Department of Agriculture (USDA) and the Food and Drug Administration (FDA) were established to keep undue amounts of pesticides out of the food chain.

Still, as with just about anything you aim to put in your mouth, a banana peel needs careful washing. That’s likely to minimize any potential pesticide menace. Even better, if you’re going to try eating the skin, consider picking up the organic variety at your local farmers market.

https://www.mnn.com/food/healthy-eating/stories/can-you-eat-banana-peel-skin?utm_source=Weekly+Newsletter&utm_campaign=e194c0c1a7-RSS_EMAIL_CAMPAIGN_WED1204_2019&utm_medium=email&utm_term=0_fcbff2e256-e194c0c1a7-40844241


Case Western Reserve researchers use AI with routine CT scans to predict how well lung cancer patients will respond to expensive treatment based off changes in texture patterns inside and outside the tumor.

Scientists from the Case Western Reserve University digital imaging lab, already pioneering the use of artificial intelligence (AI) to predict whether chemotherapy will be successful, can now determine which lung-cancer patients will benefit from expensive immunotherapy.

And, once again, they’re doing it by teaching a computer to find previously unseen changes in patterns in CT scans taken when the lung cancer is first diagnosed compared to scans taken after the first two to three cycles of immunotherapy treatment. And, as with previous work, those changes have been discovered both inside—and outside—the tumor, a signature of the lab’s recent research.

“This is no flash in the pan—this research really seems to be reflecting something about the very biology of the disease, about which is the more aggressive phenotype, and that’s information oncologists do not currently have,” said Anant Madabhushi, whose Center for Computational Imaging and Personalized Diagnostics (CCIPD) has become a global leader in the detection, diagnosis and characterization of various cancers and other diseases by meshing medical imaging, machine learning and AI.

Currently, only about 20% of all cancer patients will actually benefit from immunotherapy, a treatment that differs from chemotherapy in that it uses drugs to help your immune system fight cancer, while chemotherapy uses drugs to directly kill cancer cells, according to the National Cancer Institute.

Madabhushi said the recent work by his lab would help oncologists know which patients would actually benefit from the therapy, and who would not.

“Even though immunotherapy has changed the entire ecosystem of cancer, it also remains extremely expensive—about $200,000 per patient, per year,” Madabhushi said. “That’s part of the financial toxicity that comes along with cancer and results in about 42% of all new diagnosed cancer patients losing their life savings within a year of diagnosis.”

Having a tool based on the research being done now by his lab would go a long way toward “doing a better job of matching up which patients will respond to immunotherapy instead of throwing $800,000 down the drain,” he added, referencing the four patients out of five who will not benefit, multiplied by annual estimated cost.

Case Western Reserve researchers use AI with routine CT scans to predict how well lung cancer patients will respond to expensive treatment based off changes in texture patterns inside and outside the tumor
Scientists from the Case Western Reserve University digital imaging lab, already pioneering the use of artificial intelligence (AI) to predict whether chemotherapy will be successful, can now determine which lung-cancer patients will benefit from expensive immunotherapy.

And, once again, they’re doing it by teaching a computer to find previously unseen changes in patterns in CT scans taken when the lung cancer is first diagnosed compared to scans taken after the first two to three cycles of immunotherapy treatment. And, as with previous work, those changes have been discovered both inside—and outside—the tumor, a signature of the lab’s recent research.

“This is no flash in the pan—this research really seems to be reflecting something about the very biology of the disease, about which is the more aggressive phenotype, and that’s information oncologists do not currently have,” said Anant Madabhushi, whose Center for Computational Imaging and Personalized Diagnostics (CCIPD) has become a global leader in the detection, diagnosis and characterization of various cancers and other diseases by meshing medical imaging, machine learning and AI.

Currently, only about 20% of all cancer patients will actually benefit from immunotherapy, a treatment that differs from chemotherapy in that it uses drugs to help your immune system fight cancer, while chemotherapy uses drugs to directly kill cancer cells, according to the National Cancer Institute.

Madabhushi said the recent work by his lab would help oncologists know which patients would actually benefit from the therapy, and who would not.

“Even though immunotherapy has changed the entire ecosystem of cancer, it also remains extremely expensive—about $200,000 per patient, per year,” Madabhushi said. “That’s part of the financial toxicity that comes along with cancer and results in about 42% of all new diagnosed cancer patients losing their life savings within a year of diagnosis.”

Having a tool based on the research being done now by his lab would go a long way toward “doing a better job of matching up which patients will respond to immunotherapy instead of throwing $800,000 down the drain,” he added, referencing the four patients out of five who will not benefit, multiplied by annual estimated cost.

New research published
The figure above shows differences in CT radiomic patterns before and after initiation of checkpoint inhibitor therapy.

The new research, led by co-authors Mohammadhadi Khorrami and Prateek Prasanna, along with Madabhushi and 10 other collaborators from six different institutions was published in November in the journal Cancer Immunology Research.

Khorrami, a graduate student working at the CCIPD, said one of the more significant advances in the research was the ability of the computer program to note the changes in texture, volume and shape of a given lesion, not just its size.

“This is important because when a doctor decides based on CT images alone whether a patient has responded to therapy, it is often based on the size of the lesion,” Khorrami said. “We have found that textural change is a better predictor of whether the therapy is working.

“Sometimes, for example, the nodule may appear larger after therapy because of another reason, say a broken vessel inside the tumor—but the therapy is actually working. Now, we have a way of knowing that.”

Prasanna, a postdoctoral research associate in Madabhushi’s lab, said the study also showed that the results were consistent across scans of patients treated at two different sites and with three different types of immunotherapy agents.

“This is a demonstration of the fundamental value of the program, that our machine-learning model could predict response in patients treated with different immune checkpoint inhibitors,” he said. “We are dealing with a fundamental biological principal.”

Prasanna said the initial study used CT scans from 50 patients to train the computer and create a mathematical algorithm to identify the changes in the lesion. He said the next step will be to test the program on cases obtained from other sites and across different immunotherapy agents. This research recently won an ASCO 2019 Conquer Cancer Foundation Merit Award.

Additionally, Madabhushi said, researchers were able show that the patterns on the CT scans which were most associated with a positive response to treatment and with overall patient survival were also later found to be closely associated with the arrangement of immune cells on the original diagnostic biopsies of those patients.

This suggests that those CT scans actually appear to capturing the immune response elicited by the tumors against the invasion of the cancer—and that the ones with the strongest immune response were showing the most significant textural change and most importantly, would best respond to the immunotherapy, he said.

Madabhushi established the CCIPD at Case Western Reserve in 2012. The lab now includes nearly 60 researchers.

Some of the lab’s most recent work, in collaboration with New York University and Yale University, has used AI to predict which lung cancer patients would benefit from adjuvant chemotherapy based on tissue-slide images. That advancement was named by Prevention Magazine as one of the top 10 medical breakthroughs of 2018.

Other authors on the paper were: Germán Corredor, Mehdi Alilou and Kaustav Bera from biomedical engineering, Case Western Reserve University; Pingfu Fu from population and quantitative health sciences, Case Western Reserve University; Amit Gupta of University Hospitals Cleveland Medical Center; Pradnya Patil of Cleveland Clinic; Priya D. Velu of Weill Cornell Medicine; Rajat Thawani of Maimonides Medical Center; Michael Feldman from Perelman School of Medicine of the University of Pennsylvania; and Vamsidhar Velcheti from NYU-Langone Medical Center.

For more information, contact Mike Scott at mike.scott@case.edu.

Using artificial intelligence to determine whether immunotherapy is working

by Joe Gramigna

More than half of people who are homeless or dwell in unstable housing may have experienced a traumatic brain injury, according to results of a systematic review and meta-analysis published in The Lancet Public Health.

“Health care providers should be aware of the burden of TBI in this population,” Jacob L. Stubbs, BKin, a PhD student in the department of psychiatry at the University of British Columbia, Vancouver, told Healio Psychiatry. “Identifying a history of serious injury or new TBIs may allow for more targeted care. However, more research is urgently needed to better understand this issue.”

According to Stubbs and colleagues, a previous systematic review and previous studies have suggested that the lifetime incidence and prevalence of TBI in homeless and marginally housed individuals might be significantly higher than the general population. However, they noted that the present study is the first meta-analysis to their knowledge to evaluate TBI prevalence and incidence in these specific populations.

The researchers searched for original research studies that reported data on the association between TBI and one or more health- or function-related outcome measures, or on the prevalence or incidence of TBI. They included studies with clearly identifiable groups or subgroups of individuals who were homeless, seeking services for homeless people or marginally housed.

Among 21 studies with data from 11,417 individuals, the lifetime prevalence of any severity of TBI in homeless and marginally housed individuals was 53.4% (95% CI, 47.6-59.1). Among 12 studies with data from 6,302 individuals, the lifetime prevalence of moderate or severe TBI was 24.9% (95% CI, 16.3-35.9). Several factors significantly moderated estimated lifetime prevalence of any severity of TBI — the definition of TBI, the method used to determine TBI history and the age of the sample. The researchers noted that TBI was consistently associated with poorer self-reported mental and physical health, higher suicide risk and suicidality, memory concerns and increased criminal justice system involvement and health service use.

“Confirmation of structural brain damage caused by TBI might facilitate triage and referral to specialized services, such as cognitive rehabilitation, which could improve functional outcomes,” the researchers wrote. “Furthermore, imaging findings might positively inform the patient-caregiver relationship (eg, by increasing understanding of challenging behaviors that might be attributable to damage visible on neuroimaging).”

In a related editorial, Jesse T. Young, PhD, MPH, BSc, and Nathan Hughes, PhD, of Murdoch Children’s Research Institute in Melbourne, Australia, offered potential solutions to ameliorate the burden of TBIs among this population.

“Given the increasing evidence for a potential causal relationship, a randomized controlled trial investigating the effect of a housing intervention on TBI incidence is both feasible and warranted,” they wrote. “The Housing First model, in which homeless people are provided immediate access to permanent, noncontingent housing, has been found to reduce hospital contact for injury. Establishing the effectiveness of a Housing First approach in preventing TBI among people at risk of housing instability should be a public health priority for researchers and policy makers.”

Stubbs JL, et al. Lancet Public Health. 2019;doi:10.1016/S2468-2667(19)30188-4.
Young JT, Hughes N. Lancet Public Health. 2019;doi:10.1016/S2468-2667(19)30225-7.

https://www.healio.com/psychiatry/violence-trauma/news/online/%7B3684f5f6-57bc-4a44-92f2-1739e4a3f85e%7D/one-in-two-homeless-people-has-a-tbi?utm_source=selligent&utm_medium=email&utm_campaign=psychiatry%20news&m_bt=1162769038120

By Bryan Nelson

Many people like the idea of planting a tree next to the grave of a loved one so their bodies can live on, in a sense, by providing nutrients that get absorbed by the tree. But would you ever want to forgo the casket and the grave, and have your remains directly transformed into compost?

Washington, which earlier this year became the first state to legalize human composting, is giving residents options beyond burial or cremation.

“People from all over the state who wrote to me are very excited about the prospect of becoming a tree or having a different alternative for themselves,” state Sen. Jamie Pedersen, who sponsored the bill, told NBC News when the bill was passed.

As a result of that legislation, the first human composting site is on a path to open its doors in spring 2021 in Seattle.

The law allows for the “recomposition” of human remains, a process that speeds up decomposition and turns the remains into nutrient-packed soil, which can be used as the family sees fit. That’s where Seattle’s Recompose gets its name and its mission: “Recompose takes guidance from nature. At the heart of our model is a system that will gently return us to the earth after we die.”

The facility, which looks nothing like a traditional funeral home, will house 75 hexagonal-shaped vessels where bodies will be stored for decomposition. The breakdown takes about 30 days using wood chips, alfalfa and straw.

Cycle of life?

While some people might think there’s something eerily cannibalistic about eating crops that were planted in grandma’s remains, it’s also a way of perpetuating the cycle of life that all of our food grows from. This is the mental hurdle that has likely prevented human composting from being legalized until recently.

Recomposition does have some practical benefits that are worth considering as well. For one, it’s more economical. A traditional burial costs an average of $7,000, according to the National Funeral Directors Association. Recomposition will cost around $5,500. Moreover, composting is far healthier for the environment. No toxic embalming fluids are used, and the resultant nutrient-rich soil has a green thumb use.

There are safeguards in place to ensure that no harmful pathogens survive the recomposition process, which has been another sticking point in previous attempts to legalize human composting. A study led by researcher Lynne Carpenter-Boggs at Washington State University, which recomposed six donor bodies in a carefully controlled environment, has demonstrated that the process is safe.

https://www.mnn.com/lifestyle/responsible-living/stories/would-you-want-your-body-turned-compost-when-you-die?utm_source=Weekly+Newsletter&utm_campaign=e194c0c1a7-RSS_EMAIL_CAMPAIGN_WED1204_2019&utm_medium=email&utm_term=0_fcbff2e256-e194c0c1a7-40844241

by Gege Li

Dogs pay much closer attention to what humans say than we realised, even to words that are probably meaningless to them.

Holly Root-Gutteridge at the University of Sussex, UK, and her colleagues played audio recordings of people saying six words to 70 pet dogs of various breeds. The dogs had never heard these voices before and the words only differed by their vowels, such as “had”, “hid” and “who’d”.

Each recording was altered so the voices were at the same pitch, ensuring that the only cue the dogs had was the difference between vowels, rather than how people said the words.

After hearing the recordings just once, 48 of the dogs reacted when either the same speaker said a new word or the same word was said by a different speaker. The remainder either didn’t visibly respond or got distracted.

The team based its assessment of the dogs’ reactions on how long they paid attention when the voice or word changed – if the dogs moved their ears or shifted eye contact, for example, it showed that they noticed the change. In contrast, when the dogs heard the same word repeated several times, their attention waned.

Until now, it was thought that only humans could detect vowels in words and realise that these sounds stay the same across different speakers. But the dogs could do both spontaneously without any previous training.

“I was surprised by how well some of the dogs responded to unfamiliar voices,” says Root-Gutteridge. “It might mean that they comprehend more than we give them credit for.”

This ability may be the result of domestication, says Root-Guttridge, as dogs that pay closer attention to human sounds are more likely to have been chosen for breeding.

The work highlights the strength of social interactions between humans and dogs, says Britta Osthaus at Canterbury Christ Church University, UK. “It would be interesting to see whether a well-trained dog would react differently to the command of ‘sat’ instead of ‘sit’,” she says.

Journal reference: Biology Letters, DOI: 10.1098/rsbl.2019.0555

Read more: https://www.newscientist.com/article/2225746-dogs-have-a-better-ear-for-language-than-we-thought/#ixzz679cb3PFN


Ann Hodges (center) poses with her meteorite, underneath the point where it crashed through her house, with Sylacauga, Alabama mayor Ed Howard (left) and the town’s police chief W.D. Ashcraft. Hodges was struck by the meteorite while on her couch on Nov. 30, 1954. She donated it to the University of Alabama’s Museum of Natural History in 1956.

By Chelsea Gohd

Sixty-five years ago, a few days after Thanksgiving, Ann Hodges was snuggled up on the sofa in her Alabama home when a 4.5-billion-year-old meteorite crashed through the ceiling and struck the left side of her body. Not the best interruption to the holiday season.

The cosmic event, which took place on Nov. 30, 1954, was the first known reported instance of a human being struck by a meteorite and suffering an injury. The softball-size space rock, weighing about 8.5 lbs. (3.8 kilograms), burst through the roof of Hodges’ house in Sylacauga at 2:46 p.m. local time, bouncing off a large radio console before striking her and leaving a large, dark bruise.

The meteorite that struck Hodges, who was 31 at the time, turned out to be one-half of a larger rock that split in two as it fell toward Earth. The piece that didn’t hit Hodges landed a few miles away and is now in the collections of the Smithsonian’s National Museum of Natural History. In 2017, a 10.3-gram piece of the space rock that hit Hodges sold at auction for $7,500.

Before it ended up leaving a serious welt on Hodges’ side, people across eastern Alabama say they saw a bright light in the sky. Reports poured in of a reddish light, and some observers even described a fireball that trailed smoke and left an arc of light in the afternoon sky. After Hodges was struck and the meteorite landed, she and her mother, who was home at the time, tried to figure out what had happened.

Dust filled the house after the crash, but as it settled and they spotted the rock and the enormous bruise on Hodges, the two women called the police and fire department.

Now, as a local geologist was called to the scene to verify what the object was, word quickly spread about what happened. However, the event occurred in 1954, and not everyone was convinced that this strange rock was a meteorite. Some thought it could’ve been debris from a plane crash, and some thought it could have even come from what was then the Soviet Union.

Still, despite a few skeptics, people from all over flocked to Hodges’ home to see the woman hit by a space rock, a crowd that Hodges’ husband found as he returned from work that night. “We had a little excitement around here today,” Ann Hodges told the Associated Press. “I haven’t been able to sleep since I was hit,” she said. With all of this commotion around her, Hodges was soon hospitalized, though, despite the massive mark on her side, was not too seriously injured.

“Think of how many people have lived throughout human history,” Michael Reynolds, who wrote the book “Falling Stars: A Guide to Meteors and Meteorites,” said to National Geographic. “You have a better chance of getting hit by a tornado and a bolt of lightning and a hurricane all at the same time.”

Shockingly, Hodges is not the only person to have been hit by a meteorite, but it is still exceptionally rare.

In 2009, a 14-year-old German boy, Gerrit Blank, was hit in the hand by a pea-size meteorite. While he wasn’t seriously injured, the rock did leave a scar and gave the boy quite a fright. “When it hit me it knocked me flying and then was still going fast enough to bury itself into the road,” said Blank.

https://www.space.com/meteorite-hit-alabama-woman-65-years-ago.html?utm_source=notification

Researchers have engineered Escherichia coli bacteria to make energy exclusively from carbon dioxide, according to a paper published November 27 in Cell.

E. coli are normally heterotrophs—organisms that get their energy sources from ingesting organic compounds, such as glucose—but the new study shows that they can be turned into autotrophs, making their own energy by turning carbon dioxide from the atmosphere into biomass.

“I find it fundamentally amazing that an organism which evolved over billions of years to live a heterotrophic lifestyle can so quickly and completely change into an autotroph,” Dave Savage, a biochemist at University of California, Berkeley, who was not involved with the study, tells The Scientist in an email. “It suggests that metabolism is extremely malleable.”

This process of using inorganic carbon to make biomass, called carbon fixation, could be used to solve “some of the biggest challenges of humanity today,” Ron Milo, a systems biologist at the Weizmann Institute of Science in Israel and the lead author of the paper, tells The Scientist. For example, increasing carbon fixation in plants generates more biomass, which could increase the world’s food supply.

The team set out to make E. coli—a “very genetically malleable model organism,” says Milo—fix carbon as a step toward sustainable industrial processes such as creating biofuel.

E. coli doesn’t normally have molecular mechanisms in place to use CO2, so the researchers gave it genes for the ability to fix carbon that were based on the gene sequence of carbon-fixing Pseudomonas bacteria. These changes weren’t enough to force the bacteria to switch to being autotrophic, so the team also disabled three genes involved in heterotrophic metabolism and put the bacteria into growth chambers with limited amounts of sugar, which starved them. In this environment, there was an advantage for bacteria that used CO2 instead of the finite sugar supply, and the researchers wanted to see if the bacteria could evolve to only use CO2.

The E. coli were grown on sodium formate, a carbon molecule that donates the necessary electrons during the process of making energy, but doesn’t contribute to biomass. The air in the growth chambers was also enriched with carbon dioxide.

After approximately 200 days, the bacteria relied completely on carbon dioxide from the air to generate biomass while taking in formate as a necessary ingredient for the chemical reactions. When the scientists analyzed the bacterial genome, they found that the bacteria evolved to use carbon dioxide as their energy source after as few as 11 mutations. Some of the changes occurred in genes related to carbon fixation, while others were in genes that are known to mutate in other lab evolution experiments or have no known role in energy production from CO2.


Heterotrophic E. coli (left) produce biomass from sugar, but lab-evolved autotrophic E. coli from the new study (center) use CO2 instead. The authors envision autotrophic E. coli that use renewable energy and have no net carbon emissions in the future (right).

“It’s a proof of concept for the field, that you can really rewire . . . the metabolic features of living organisms from scratch. It’s an exciting step forward,” Tobias Erb, a synthetic biologist at the Max Planck Institute for Terrestrial Microbiology in Germany who wrote a commentary on the study, tells The Scientist. However, “if the strain that they created [is] of biotechnological relevance in the future . . . I think is still up to debate,” he says.

For instance, the autotrophic E. coli currently produce more carbon dioxide as a byproduct than they take in. This could be solved by producing formate from carbon dioxide in the future, so that there are no net carbon dioxide emissions.

In addition, the researchers used high carbon dioxide levels in the bacteria’s growth chambers—around 10 percent of the air—but it’s only 0.04 percent of Earth’s atmosphere. “We’re interested to see if we could move it towards ambient carbon dioxide levels, meaning that one could use the ambient atmosphere that has much less [carbon dioxide], 400 parts per million,” says Milo.

“It’s an interesting concept now. Whether it actually is something that becomes useful in terms of application, that’s another question,” Patrik Jones, who studies microbial metabolic engineering at Imperial College London and was not involved with the study, tells The Scientist. “It’s definitely a step towards that direction . . . But then I think it’s important to realize that there are more steps needed in order to utilize this.”

ABOVE: FLICKR.COM, NIAID
Researchers have engineered Escherichia coli bacteria to make energy exclusively from carbon dioxide, according to a paper published today (November 27) in Cell.

E. coli are normally heterotrophs—organisms that get their energy sources from ingesting organic compounds, such as glucose—but the new study shows that they can be turned into autotrophs, making their own energy by turning carbon dioxide from the atmosphere into biomass.

“I find it fundamentally amazing that an organism which evolved over billions of years to live a heterotrophic lifestyle can so quickly and completely change into an autotroph,” Dave Savage, a biochemist at University of California, Berkeley, who was not involved with the study, tells The Scientist in an email. “It suggests that metabolism is extremely malleable.”

This process of using inorganic carbon to make biomass, called carbon fixation, could be used to solve “some of the biggest challenges of humanity today,” Ron Milo, a systems biologist at the Weizmann Institute of Science in Israel and the lead author of the paper, tells The Scientist. For example, increasing carbon fixation in plants generates more biomass, which could increase the world’s food supply.

The team set out to make E. coli—a “very genetically malleable model organism,” says Milo—fix carbon as a step toward sustainable industrial processes such as creating biofuel.

E. coli doesn’t normally have molecular mechanisms in place to use CO2, so the researchers gave it genes for the ability to fix carbon that were based on the gene sequence of carbon-fixing Pseudomonas bacteria. These changes weren’t enough to force the bacteria to switch to being autotrophic, so the team also disabled three genes involved in heterotrophic metabolism and put the bacteria into growth chambers with limited amounts of sugar, which starved them. In this environment, there was an advantage for bacteria that used CO2 instead of the finite sugar supply, and the researchers wanted to see if the bacteria could evolve to only use CO2.

The E. coli were grown on sodium formate, a carbon molecule that donates the necessary electrons during the process of making energy, but doesn’t contribute to biomass. The air in the growth chambers was also enriched with carbon dioxide.

After approximately 200 days, the bacteria relied completely on carbon dioxide from the air to generate biomass while taking in formate as a necessary ingredient for the chemical reactions. When the scientists analyzed the bacterial genome, they found that the bacteria evolved to use carbon dioxide as their energy source after as few as 11 mutations. Some of the changes occurred in genes related to carbon fixation, while others were in genes that are known to mutate in other lab evolution experiments or have no known role in energy production from CO2.

Heterotrophic E. coli (left) produce biomass from sugar, but lab-evolved autotrophic E. coli from the new study (center) use CO2 instead. The authors envision autotrophic E. coli that use renewable energy and have no net carbon emissions in the future (right).
GLEIZER ET AL.
“It’s a proof of concept for the field, that you can really rewire . . . the metabolic features of living organisms from scratch. It’s an exciting step forward,” Tobias Erb, a synthetic biologist at the Max Planck Institute for Terrestrial Microbiology in Germany who wrote a commentary on the study, tells The Scientist. However, “if the strain that they created [is] of biotechnological relevance in the future . . . I think is still up to debate,” he says.

For instance, the autotrophic E. coli currently produce more carbon dioxide as a byproduct than they take in. This could be solved by producing formate from carbon dioxide in the future, so that there are no net carbon dioxide emissions.

In addition, the researchers used high carbon dioxide levels in the bacteria’s growth chambers—around 10 percent of the air—but it’s only 0.04 percent of Earth’s atmosphere. “We’re interested to see if we could move it towards ambient carbon dioxide levels, meaning that one could use the ambient atmosphere that has much less [carbon dioxide], 400 parts per million,” says Milo.

“It’s an interesting concept now. Whether it actually is something that becomes useful in terms of application, that’s another question,” Patrik Jones, who studies microbial metabolic engineering at Imperial College London and was not involved with the study, tells The Scientist. “It’s definitely a step towards that direction . . . But then I think it’s important to realize that there are more steps needed in order to utilize this.”

Emily Makowski is an intern at The Scientist. Email her at emakowski@the-scientist.com.

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