Swedish freshwater bacteria give new insights into bacterial evolution

Stockholm University

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Unlike most bacteria, Caulobacterales bacteria divide asymmetrically when they reproduce, which creates two cells that look different from each other (top part of the illustration). However, the researchers at Stockholm University discovered that several species have lost this complexity during their evolution (bottom part of the illustration), and that these species are missing around 100 specific genes. This gives the researchers a unique window into which genes are needed to create complex lifecycles in bacteria.

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Credit: Joel Hallgren

Bacteria are among the most diverse and ancient forms of life on Earth. Yet, much of what we know about them comes from a small group of species, mostly studied for their roles in human health.

“The vast majority of bacterial species remain unexplored, and this really limits our understanding of how bacteria shape ecosystems and have evolved to thrive in different environments,” says Joel Hallgren, lead author of the study.

Most bacteria reproduce through simple, symmetrical cell division. However, members of one distinctive group, the Caulobacterales, known for their “stalked” appearance, deviate from this pattern. They have a more complex lifecycle, involving asymmetric cell division that results in two distinct cell types: one mobile and explorative, and the other sessile and reproductive. The evolutionary reasons behind this complex lifecycle have long puzzled scientists. Caulobacterales bacteria are also known to be environmentally widespread and are thought to be important degraders of plant matter in nature, but their ecology and evolution have remained poorly studied.

Researchers at Stockholm University analyzed the DNA of all known Caulobacterales species, including newly collected samples from Swedish and Finnish forest lakes. They discovered that several freshwater species lacked more than a hundred genes typically linked to the group’s complex lifecycle. These bacteria represent three new species in a previously unknown genus, which the team named Acaudatibacter, Latin for “bacterium without a tail.”

Intriguingly, another soil Caulobacterales member, isolated in Ecuador, also lacked the same set of lifecycle genes and, as the researchers observed by microscopy, reproduces through simple, symmetric cell division. This independent loss of complexity in separate lineages provides insight into the set of genes essential for the complex lifecycles of bacteria.

“It’s fascinating to see that evolution has reversed lifecycle complexity multiple times in the same way,” says Joel Hallgren. “It gives us a unique genetic signature of how complexity arises, and disappears, during the evolution of bacterial lifecycles.”

The researchers also made another unexpected discovery: the Swedish lake bacteria possessed all the genes required for photosynthesis, a capability not previously known in Caulobacterales, highlighting that photosynthesis is more widespread among bacteria than previously thought. Indeed, further analysis revealed that roughly 10% of species in this group carry genes for harvesting light energy.

“It’s exciting that novel bacterial species from my own country are giving us new perspectives on fundamental concepts in microbiology,” says Hallgren.

The study was a close interdisciplinary collaboration between two research groups at Stockholm University, both based at SciLifeLab, a national infrastructure for life sciences, when the work began.

“This project combined my lab’s expertise in bacterial cell biology and genetics with the strong microbial genomics and ecology expertise of Sarahi Garcia’s group,” says senior author Kristina Jonas. “Our affiliation with SciLifeLab and the flexible funding it provided made it possible for us to explore this new research direction.”

 

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Journal

Nature Communications

DOI

10.1038/s41467-025-65642-x 

Method of Research

Experimental study

Subject of Research

Cells

Article Title

Widespread potential for phototrophy and convergent reduction of lifecycle complexity in the dimorphic order Caulobacterales

Article Publication Date

12-Dec-2025

 

Hidden patterns of isolation and segregation found in all American cities

University College London

A comprehensive analysis of 383 U.S. cities reveals a striking pattern: most have rings of isolation in suburban areas and segregated pockets of near the urban core, that are shaped by race, wealth, and proximity to downtown, finds a new study by UCL researchers.

Published in Nature Cities, the paper analyses the daily movements of people in cities right across America and found common patterns prevalent in every city analysed.

Using anonymised mobile phone SafeGraph GPS location data, researchers mapped the movement of millions of people over a four-year period, as they travelled from home neighbourhoods to places such as restaurants, shops, museums and hospitals. They combined this information with census block group data* on their home areas to estimate an individual’s likely median income and the demographic makeup of the area.

The authors revealed most U.S. cities have, “isolated” wealthier suburban neighbourhoods on the cities’ periphery, which are often majority white, and have few visitors from different socio-economic backgrounds. There are also other “segregated” poorer downtown areas, often majority non-white, where residents have few interactions with people of different backgrounds than them.

Lead author, PhD candidate Andrew Renninger (UCL Centre for Advanced Spatial Analysis), said: “Cities are supposed to be melting pots - places where people from different backgrounds mix, share ideas, and create opportunities. That’s what makes cities engines of innovation and wealth. But our research shows that many U.S. cities are divided by invisible boundaries that shape who interacts with whom every single day.”

This study is the first to look at this kind of data on what researchers call the ‘mesoscale’ —the neighbourhood level between individual and city-wide analysis.

Andrew Renninger added: “Tracking these networks is important because a lack of connections between residents of a neighbourhood and the wider city and broader economy can fuel inequality in creating a disadvantage for those residents while also limiting growth for the whole city.”

Researchers found that every city studied contained segregated pockets—areas where local amenities are mostly visited by people from the same neighbourhood or socio-economic background. While residents of these areas may travel elsewhere, outsiders rarely visit, limiting social diversity. These segregated zones are often poorer and predominantly non-white, with race and income strongly influencing integration. Amenities near downtown tend to attract more diverse visitors—except in majority non-white areas—while neighbourhoods farther from the centre are typically more isolated unless they are majority non-white.

Andrew Renninger added: “Much of this can be traced to historic discriminatory housing practices by federal, state or local governments that helped to create this segregation. The researchers point to areas such as South Central Los Angeles, South Side Chicago, and South Bronx in New York as such segregated pockets.”

Around the suburban edges of most cities lie rings of isolation, where residents mainly interact with others of similar income or ethnicity. These communities tend to visit amenities that are themselves segregated, meaning their daily routines rarely reflect the diversity of the wider city. Such isolated rings are typically more affluent than the urban core.

Effect of COVID-19 pandemic

The timeframe of the analysis stretched from January 2019 through December 2022 providing insights into how the pandemic affected people’s movements. The team found that, expectedly, segregation and isolation peaked in April of 2020, during the pandemic, but levels largely returned to pre-pandemic norms by 2022, except for some cities like Boston and San Francisco, where isolation remained higher.

Co-author Professor Elsa Arcaute (UCL Centre for Advanced Spatial Analysis) said: “COVID-19 effectively created a large-scale social experiment in which more localised living revealed its potential downsides, namely, increased segregation and reduced exposure to diversity. It reveals that not all aspects of daily life can—or should—be localised; pushing all activities to the neighbourhood scale risks reinforcing the very patterns of isolation we seek to avoid.”

The researchers recommend that using these kinds of data, cities could use zoning and land use incentives to develop clusters of amenities in accessible areas between zones and invest in downtown to encourage greater social mixing.

Co-author Professor Neave O’Clery (UCL Centre for Advanced Spatial Analysis) said: “Our research offers policymakers and planners valuable insights for developing amenities around cities that can encourage greater diversity and social mixing. By encouraging more strategic development, it can help isolated residents better connect with the broader community and economy, reducing inequality.”

* While the primary analysis focuses on income-based segregation, patterns strongly correlate with racial composition and historic discriminatory housing practices. Race was not directly measured; instead, demographic context was inferred from neighbourhood-level census data.

 

Notes to Editors

For more information or to speak to the researchers involved, please contact Michael Lucibella, UCL Media Relations. T: +44 (0)75 3941 0389, E: m.lucibella@ucl.ac.uk

Andrew Renninger, Neave O’Clery, and Elsa Arcaute, ‘US cities are defined by rings and pockets with limited socioeconomic mixing’ will be published in Nature Cities on Friday 12 December 2025, 10:00 UK time, 05:00 US Eastern Time and is under a strict embargo until this time.

The DOI for this paper will be: https://doi.org/10.1038/s44284-025-00350-7

The URL for this paper will be: https://www.nature.com/articles/s44284-025-00350-7

Additional material

• Andrew Renninger’s academic profile
• Professor Neave O’Clery’s academic profile
• Elsa Arcaute’s academic profile
• UCL Bartlett Centre for Advanced Spatial Analysis
• UCL Bartlett Faculty of the Built Environment

 

About UCL – London’s Global University

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Since 1826, we have championed independent thought by attracting and nurturing the world's best minds. Our community of more than 50,000 students from 150 countries and over 16,000 staff pursues academic excellence, breaks boundaries and makes a positive impact on real world problems.

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Journal

Nature Cities

DOI

10.1038/s44284-025-00350-7 

Method of Research

Data/statistical analysis

Subject of Research

People

Article Title

US cities are defined by rings and pockets with limited socioeconomic mixing

Article Publication Date

12-Dec-2025

 

FDA drug trials exclude a widening slice of Americans

Insufficient racial representation reduces confidence in drug efficacy and safety

University of California - Riverside

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Chart indicating declining representation for Black and Hispanic groups in clinical trials.

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Credit: Zaaijer, S., Groen, S.C./Commun Med/2025

A new study finds just 6% of clinical trials used to approve new drugs in the U.S. reflect the country’s racial and ethnic makeup, with an increasing trend of trials underrepresenting Black and Hispanic individuals.

The findings arrive amidst a push for personalized medicine, which creates treatments designed specifically for an individual’s genetic makeup. 

Researchers at UC Riverside and UC Irvine examined data from 341 pivotal trials—the large, final-stage studies used to gain FDA approval for new drugs—between 2017 and 2023. They observed a decline in Black and Hispanic enrollment beginning in 2021, even as calls for greater equity in science and medicine intensified. Asian representation increased over this period, while white participation remained largely stable.

“Precision medicine relies on understanding how genetic differences influence treatment outcomes,” said Sophie Zaaijer, a geneticist with both UCR and UC Irvine, and co-lead author of the study. “If clinical trials under-sample large segments of human genetic variation, critical signals for safety and efficacy may be missed.”

Zaaijer and co-author Simon “Niels” Groen, a UCR geneticist, argue that while ancestry alone shouldn’t guide clinical treatment decisions, it plays a critical role in the early stages of drug development. People from different backgrounds often carry different versions of genes, called alleles, that affect how the body responds to medications.

“When a trial includes only a narrow slice of humanity, we can’t be confident a drug will work — or be safe — for everyone it’s meant to help,” Groen said.

Clinical trials used to approve drugs in the United States are conducted both in the U.S. and in other countries that follow International Council for Harmonisation, or ICH, standards. While this ensures consistency between trials and speeds up approvals, it also concentrates evidence in a few regions such as the U.S., Europe, China, and Japan. 

Sub-Saharan Africa and much of Latin America, which host less than 3% of pivotal trials, are often left out of the data that shapes medicines used by millions of Americans.

This could be changing for Hispanics. Brazil joined ICH in 2016, followed by Mexico in 2021 and Argentina in 2024. Expanding trial networks to these and other underrepresented regions may help future studies better capture the genetic variation of patients worldwide.

Zaaijer began this line of research as a postdoctoral fellow at Cornell Tech, studying how little human genetic diversity is taken on board in preclinical drug development when patient-derived cells are used to model disease and test potential therapies. 

“I kept wondering,” Zaaijer said, “If our preclinical models are this skewed, what happens once those drugs move into clinical trials?” Bias in preclinical models is an early warning sign, but bias in clinical trials becomes medical practice, she noted. 

Her collaboration with Groen’s lab developed naturally. His lab at UCR studies how tiny worms metabolize plant toxins, and the parallels with human biology are striking. “Many of the same genes used to break down chemicals in worms are also involved in drug metabolism in humans,” Groen said.

“The genes worms use to detoxify chemicals are ancient,” Groen continued. “We carry many of the same ones. But small natural variations in forms of these genes can have a big effect.”

Published in Communications Medicine, the study offers several recommendations: set diversity goals at the beginning of the drug development pipeline at the preclinical stage, choose testing locations that reflect the health needs and genetic backgrounds of local populations, and collect biological samples, such as blood or saliva, that can help researchers understand how people’s bodies react to a drug. 

Even as DNA testing becomes more common in doctor’s offices, the researchers stress that realizing the full promise of personalized medicine depends on stronger, more ancestry-aware data from the start.

“Precision medicine becomes possible only when clinical trials map the biology of all patients, not just a subset,” Groen said. “Our analysis could offer a roadmap for how to get there.”

 

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Journal

Communications Medicine

DOI

10.1038/s43856-025-01270-2 

Article Title

Longitudinal clinical trial enrollment trends across 341 US FDA-approved drugs and their guiding role in precision medicine strategies

Article Publication Date

5-Dec-2025

 

Acupuncture may help improve perceived breast cancer-related cognitive difficulties over usual care

American Association for Cancer Research

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SAN ANTONIO – Real and sham acupuncture were more effective at improving breast cancer survivors’ perceived cognitive impairment compared with usual care, while real acupuncture was superior to sham acupuncture in improving objective cognitive function, according to results from the randomized ENHANCE phase II clinical trial presented at the San Antonio Breast Cancer Symposium (SABCS), held December 9-12, 2025.

More than 40% of breast cancer survivors experience cancer-related cognitive difficulties, which are sometimes referred to as “brain fog” or “chemo-brain,” according to Jun J. Mao, MD, MSCE, the Laurance S. Rockefeller chair in integrative medicine and chief of integrative medicine and wellness service at Memorial Sloan Kettering Cancer Center. “Cancer-related cognitive difficulties can make performing daily tasks more difficult and can reduce overall quality of life,” Mao explained. “Unfortunately, there are very few treatments that are backed by evidence for this problem.”

Previously, Mao and his colleagues found that insomnia was associated with cognitive difficulties in over 1,000 breast cancer survivors and that, in a prior trial, acupuncture improved insomnia and may improve cognitive function compared with cognitive behavioral therapy for insomnia (CBT-I). To further test the effectiveness of acupuncture in improving cognitive function for breast cancer patients, the researchers designed a three-arm study comparing real acupuncture to sham acupuncture and usual care given at the physician’s discretion. Sham acupuncture is designed to mimic the experience of real acupuncture with a similar overall relaxing experience, but there are a few key differences: Sham acupuncture uses locations on the body that are not considered classic acupuncture points, and the needles do not penetrate the skin.

“Acupuncture should be seen as a complex intervention that involves both the needling and the care being delivered,” Mao explained. “Just believing you’re receiving a helpful treatment and engaging in relaxation by lying down for 20-30 minutes can have potential therapeutic benefits even if the needles aren’t inserted or aren’t placed in specific therapeutic points. By comparing real acupuncture to sham acupuncture, and not just to usual care, we were able to better understand whether the benefits were due to the acupuncture technique itself or to the overall experience.”

The clinical trial enrolled 260 women with a history of stage 0-3 breast cancer who completed treatment, showed no signs of cancer, and self-reported moderate or greater cancer-related cognitive difficulties and insomnia. Participants were randomly assigned to receive real acupuncture (129), sham acupuncture (70), or usual care (61). Real or sham acupuncture treatments were delivered once weekly for 10 weeks, and cognitive function was evaluated at baseline, 10 weeks, and 26 weeks.

Perceived cognitive function was measured using the Functional Assessment of Cancer Therapy - Cognitive Function (FACT-Cog PCI), a validated patient-reported outcome that asks patients to complete a survey about how they feel their memory, attention, and ability to perform daily tasks have been affected. Objective cognitive function was measured via the Hopkins Verbal Learning Test-Revised (HVLT), which measures memory, learning, or attention performance using standardized tasks.

“These two measures capture different aspects of cognition and often don’t align,” Mao said. “In our study, among participants who reported moderate to severe cognitive difficulties and met eligibility for enrollment, only 30% met the criteria for objective cognitive impairment as measured by the HVLT. This mismatch highlights the importance of using both tools together as they provide a more complete picture.”

After 10 weeks, those in the real acupuncture and sham acupuncture arms showed clinically meaningful improvement in perceived cognitive impairment as measured by FACT-Cog PCI scores: a 10.3-point improvement and 10.5-point improvement, respectively, compared with a 4.8-point improvement in the usual care group. Real acupuncture also showed a twofold improvement at reducing perceived cognitive impairment compared with usual care at both 10 weeks and 26 weeks, while the difference between real and sham acupuncture was not significant at either point.

“The fact that real and sham acupuncture produced similar effects in improving perceived cognitive function may be because sham acupuncture, although not stimulating the body in the same way, still offers benefits like personal attention, relaxation, and a sense of being cared for, all of which can improve how people feel,” Mao explained.

While real acupuncture improved HVLT scores, sham acupuncture had no difference on objective cognition function. At week 10, real acupuncture was significantly better than sham acupuncture with a 4-point difference in HVLT scores. Overall, real acupuncture and usual care showed similar results at improving objective cognitive function. However, in the subset of patients who were found to have impaired objective cognitive function at baseline, real acupuncture was associated with a promising trend in improving memory compared with usual care and sham acupuncture.

“Previous research using brain scans in people with memory issues or with pain suggests that real acupuncture may more effectively stimulate specific areas of the brain involved in memory, attention, and learning,” Mao explained. “While our study also shows that acupuncture needling may have potential benefit for improving objective cognitive function for those with some impairment, future studies are needed to specifically verify this.”

Adverse events were mostly mild and limited to the real acupuncture arm with bruising being the most common (3.1% of participants). Outside of acupuncture, the study also found that insomnia was significantly linked to objective cognitive performance and that sleep fragmentation—the number of awakenings and awakening time—was significantly associated with worse performance on objective cognitive tests.

“Cognitive difficulties for women with breast cancer are complex and involve finding ways to address both the distress associated with perceived cognitive abilities as well as objective function,” Mao said. “While this trial showed that acupuncture’s ability to improve a patient’s perceived cognitive difficulty is likely due to the process of receiving acupuncture care rather than specific needling techniques, it is still reasonable for women with breast cancer to try a course of acupuncture to see if it can help improve their sense of cognitive difficulty. It may also benefit objective cognitive function, but we hope future trials with larger samples of patients with objective cognitive impairment will provide more conclusive evidence.”

Limitations of this study include a small sample of patients who met the criteria for objective cognitive impairment at baseline. The trial was also conducted at a single, large, urban academic cancer center with participants limited to female breast cancer survivors, so results may not be generalizable to male survivors, survivors with other cancer types, or survivors in community or rural settings. The trial was conducted during the COVID-19 pandemic, which may have introduced other variables related to a patient’s stress and care.

This study was funded by grants from the National Cancer Institute and the National Institutes of Health’s Cancer Center Support Grant. Mao declares receiving funds from Tibet Cheezheng Tibetan Medicine Co., Ltd. and Zhongke Health International LLC for other work. He is also a cofounder of Greatly Health.

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COI Statement

This study was funded by grants from the National Cancer Institute and the National Institutes of Health’s Cancer Center Support Grant. Mao declares receiving funds from Tibet Cheezheng Tibetan Medicine Co., Ltd. and Zhongke Health International LLC for other work. He is also a cofounder of Greatly Health.