Identical micro-animals live in two isolated deep-sea environments. How is that possible?

The researchers traveled on the research vessel Polarstern to South Sandwich Trench where they collected sediment samples.
Photo Credit: ©Anni Glud/SDU

Halalaimus is a microscopic nematode genus commonly found in sediment on the seafloor. It lives 1–5 cm below the sediment surface and grazes on bacteria or organic materials in the sediment. 

It does so in the Aleutian Trench as well, which lies in the northern Pacific Ocean, near the Bering Sea. We now know this because PhD Yick Hang Kwan from Danish Center for Hadal Research at the Department of Biology has isolated its eDNA in sediment samples collected from the depths of the Aleutian Trench. 

“But we also found its eDNA in sediment samples from the South Sandwich Trench, which lies 17,000 km away in the South Atlantic. And that inevitably makes you ask: How is it possible that the same nematode genus exists in such extremely isolated deep-sea environments so far apart, when it has a very limited ability to move – and when the trenches are up to eight kilometers deep?” Kwan asks rhetorically. 

Immune system keeps mucosal fungi in check

The yeast fungus Candida albicans (blue) breaks out of human immune cells (red) by forming long thread-like cells called hyphae. The part of the hypha that has already left the immune cells is colored yellow.
Image Credit: Erik Böhm, Leibniz-HKI

The yeast Candida albicans colonizes mucosal surfaces and is usually harmless. However, under certain conditions it can cause dangerous infections. A research team at the University of Zurich has now discovered how the immune system prevents the transformation from a harmless colonizer to a pathogenic mode. This happens, among other things, by sequestering zinc. 

The microbiome not only consists of bacteria, but also of fungi. Most of them support human and animal health. However, some fungi also have pathogenic potential. For instance, the yeast Candida albicans can grow in an uncontrolled manner on the oral mucosa, causing oral thrush. 

In severe cases by growing in a filamentous form, it can enter the bloodstream and cause systemic infections, which account for over one million deaths per year. This happens primarily in people with a weakened immune system on intensive care units, for instance individuals who are immunosuppressed because of a transplantation or cancer. 

Surfing on the waves of the microcosm

A particle (red sphere) is guided from left to its destination (right) using a laser trap (double-cone) by means of a protocol developed in the study, which is described by the parameter λ. A known time-dependent external force field F (t) acts on this environment. The optimised protocol exploits this force field in a way that extracts the maximum amount of work. This can be applied to various external fields, to active particles and to micro-robot transport problems. 
Image Credit: HHU/Kristian S. Olsen

Conditions can get rough in the micro- and nanoworld. To ensure that e.g. nutrients can still be optimally transported within cells, the minuscule transporters involved need to respond to the fluctuating environment. Physicists at Heinrich Heine University Düsseldorf (HHU) and Tel Aviv University in Israel have used model calculations to examine how this can succeed. They have now published their results – which could also be relevant for future microscopic machines – in the scientific journal Nature Communications. 

When planning an ocean crossing, sailors seek a course, which makes optimum use of favorable wind and ocean currents, and maneuver to save time and energy. They also react to random fluctuations in wind and currents and take advantage of fair winds and waves. Such considerations regarding energy costs are also important for transport processes at the micro- and nanoscale. For example, molecular motors should use as little energy as possible when transporting nutrients from A to B between and within biological cells.  

Scientists create stable, switchable vortex knots inside liquid crystals

Vortex knots inside a chiral nematic liquid crystal
Image Credit: Ivan Smalyukh

The knots in your shoelaces are familiar, but can you imagine knots made from light, water, or from the structured fluids that make LCD screens shine? 

They exist, and in a new Nature Physics study, researchers created particle-like so-called “vortex knots” inside chiral nematic liquid crystals, a twisted fluid like those used in LCD screens. For the first time, these knots are stable and could be reversibly switched between different knotted forms, using electric pulses to fuse and split them. 

“These particle-like topological objects in liquid crystals share the same kind of topology found in theoretical models of glueballs, experimentally-elusive theoretical subatomic particles in high-energy physics, in hopfions and heliknotons studied in light, magnetic materials, and in vortex knots found across many other systems,” explains Ivan Smalyukh, director of the Hiroshima University WPI-SKCM² Satellite at the University of Colorado Boulder and a professor in CU Boulder’s Department of Physics. 

Rice researchers uncover the hidden physics of knot formation in fluids

From left to right, top to bottom: Sibani Lisa Biswal, Fred MacKintosh, Lucas H.P. Cunha and Luca Tubiana.
Photo Credit: Courtesy of Rice University

Knots are everywhere — from tangled headphones to DNA strands packed inside viruses — but how an isolated filament can knot itself without collisions or external agitation has remained a longstanding puzzle in soft-matter physics.

Now, a team of researchers at Rice University, Georgetown University and the University of Trento in Italy has uncovered a surprising physical mechanism that explains how a single filament, even one too short or too stiff to easily wrap around itself, can form a knot while sinking through a fluid under strong gravitational forces. The discovery, published in Physical Review Letters, provides new insight into the physics of polymer dynamics, with implications ranging from understanding how DNA behaves under confinement to designing next-generation soft materials and nanostructures.

“It is inherently difficult for a single, isolated filament to knot on its own,” said Sibani Lisa Biswal, corresponding author, chair of Rice’s Department of Chemical and Biomolecular Engineering and the William M. McCardell Professor in Chemical Engineering. “What’s remarkable about this study is that it shows a surprisingly simple and elegant mechanism that allows a filament to form a knot purely because of stochastic forces as it sediments through a fluid under strong gravitational forces.”

AI helps explain how covert attention works and uncovers new neuron types

Image Credit: Scientific Frontline / AI generated

Shifting focus on a visual scene without moving our eyes — think driving or reading a room for the reaction to your joke — is a behavior known as covert attention. We do it all the time, but little is known about its neurophysiological foundation. Now, using convolutional neural networks (CNNs), UC Santa Barbara researchers Sudhanshu Srivastava, Miguel Eckstein and William Wang have uncovered the underpinnings of covert attention and, in the process, have found new, emergent neuron types, which they confirmed in real life using data from mouse brain studies. 

“This is a clear case of AI advancing neuroscience, cognitive sciences and psychology,” said Srivastava, a former graduate student in the lab of Eckstein, now a postdoctoral researcher at UC San Diego. 

Climate shapes arms race between ants and their social parasites

The "slave-making ant" Temnothorax americanus (left) and its host Temnothorax longispinosus
Photo Credit: ©: Romain Libbrecht

The battle between ant hosts and their social parasites is strongly influenced by climate. Temperature and humidity shape how the ants behave, communicate, and even evolve — while host and parasite respond with very different genetic strategies. These are the findings of two recent studies in which researchers at Johannes Gutenberg University Mainz (JGU) and the Senckenberg Biodiversity and Climate Research Centre combined behavioral experiments with state-of-the-art genomic analyses. "Climate clearly explains the variation in host and parasite behavior better than parasite prevalence itself," says Professor Susanne Foitzik, senior author of both studies and chair of Behavioral Ecology and Social Evolution at JGU.

In the first study, published in the Journal of Evolutionary Biology, the team examined a parasite, the so-called "slave-making ant" Temnothorax americanus, and its host, the ant Temnothorax longispinosus. The social parasite invades host nests and steals their brood, which later grows up to work for the parasite colony – an extraordinary form of social parasitism. The researchers focused on how the ants' behavior and chemical communication vary across different climates. By comparing ten natural populations along a 1,000‑kilometer north-south gradient in the United States, they found that climate influenced the conflict more strongly than the local frequency of parasite colonies.

Biodegradable wet wipes remain in rivers for more than five weeks

Photo Credit: Christine Sandu

Scientists have tested, for the first time, how biodegradable wet wipes break down when flushed rather than composted discovering that most wipes remain after five weeks – a finding the research team says challenges the marketing of these products. 

Researchers from Cardiff University’s Schools of Biosciences, Chemistry and Engineering tested two widely available brands of wipes labelled as ‘biodegradable’ in ten urban rivers and streams in Cardiff, UK 

For five weeks, the team tracked the degradation of the wet wipes in these locations by testing their tensile strength loss, and recording environmental factors such as microbial biomass, water chemistry, temperature, and river-level fluctuations. 

Stroke and dementia: combating loss of function in small vessels of the brain

Professor Martin Dichgans
Photo Credit: © LMU / Stephan Höck

Researchers at LMU University Hospital have elucidated how diseases of small blood vessels in the brain develop. So-called cerebral small vessel disease (CSVD) can lead to widespread consequences such as circulatory disorders, hemorrhages, and often severe strokes, and is considered one of the main causes of dementia. The scientists' results have now been published in the journal Nature Neuroscience. 

In view of the prevalence of this serious and life-threatening condition—strokes, for example, are the leading cause of long-term disability and the second leading cause of death—it is astonishing "that medicine has so far known comparatively little about the cellular and molecular mechanisms underlying the development of cerebral small vessel disease," says LMU Professor Martin Dichgans, Chair of Translational Stroke and Dementia Research, Director of the Institute for Stroke and Dementia Research (ISD) at LMU University Hospital Munich, and future spokesperson for the SyNergy Cluster of Excellence. 

Fine particles in pollution are associated with early signs of autoimmune disease

Photo Credit: Chris LeBoutillier

A new study has linked air pollution exposure and immune-system changes that often precede the onset of autoimmune diseases. 

McGill University researchers analyzing Ontario data found that fine particles in air pollution are associated with higher levels of a biomarker linked with autoimmune diseases, such as systemic lupus. 

“These results point us in a new direction for understanding how air pollution might trigger immune system changes that are associated with autoimmune disease,” said Dr. Sasha Bernatsky, a James McGill Professor of Medicine and member of the McGill Centre for Climate Change and Health, the Division of Rheumatology and the Centre for Outcome Research and Evaluation. “We know some genetic factors play a role in autoimmune disease, but they don’t tell the whole story.”