Tag Archives: SingleCelled

Discover the Geometry of a Trumpet-Shaped Single-Celled Microorganism

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A fascinating protist species known as the blue spot stentor demonstrates remarkable movement by perceiving physical shapes. This finding implies that even the most basic life forms can utilize geometry for survival.

blue spot stentor. Image credit: Hokkaido University Physical Behavior Laboratory.

Measuring just 1mm in length, the blue spot stentor belongs to the protist family Tentriidae.

According to Dr. Shun Echigoya from Hokkaido University, lead author of the study, blue spot stentor exhibit complex behaviors that toggle between free-swimming and anchoring to substrates.

While swimming, the blue spot stentor generates propulsive force through hair-like structures called membranous bands located at the anterior end.

These cells adjust their movement in response to light and chemical signals while exploring their environment.

During swimming, the blue spot stentor elongates into a trumpet shape and anchors itself to the substrate using a fixation organ at the back.

When anchored, blue spot stentor also creates external vortices via its membranous band, forming an oral apparatus that traps bacteria and small ciliates for food.

However, the researchers noted that being anchored may increase vulnerability to predation.

Thus, selecting anchor points in a varied environment is crucial for the blue spot stentor.

For this study, Dr. Echigoya and colleagues crafted small chambers with controlled shapes, simulating the structures microorganisms encounter in natural aquatic habitats.

Some chambers featured smooth surfaces, while others included narrow spaces imitating edges, angles, and corners.

“We adjusted geometric characteristics such as corner angles and depths to provide varied anchorage options,” Dr. Echigoya elaborated.

“We documented the microorganisms’ behaviors through video recordings and supplemented them with numerical simulations for detailed analysis.”

The researchers observed behavior that was anything but random.

Initially, the cells swam freely, but as they neared the surface, their behavior transformed.

Their bodies became subtly asymmetrical, allowing them to glide along walls using the coordinated beating of their cilia.

Over time, they navigated toward smaller crevices, where they secured themselves to the surface.

“We were surprised by the effectiveness of this minimal strategy,” Dr. Echigoya stated.

The blue spot stentor does not require cognitive awareness of its surroundings; it can interact physically with surfaces simply by altering its shape to find suitable nooks.

“Our findings indicate that even slight physical features in natural environments significantly influence where microorganisms thrive and how they proliferate,” remarked Dr. Yukinori Nishigami, study co-author from Hokkaido University.

“The microscopic landscape is filled with tiny crevices and safe spaces.”

“Possessing the ability to locate and inhabit these protected niches may explain how microorganisms survive, disperse, and establish communities.”

The complete findings are published in Proceedings of the National Academy of Sciences.

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Echigoya Shun et al. 2026. Geometric preference of anchor sites in unicellular organisms: blue spot stentor. PNAS 123 (9): e2518816123; doi: 10.1073/pnas.2518816123

Source: www.sci.news

Brainless Single-Celled Organisms Exhibit Pavlovian Learning Abilities

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Stentor coeruleus – A remarkable single-celled organism

Melba Photo Agency / Alamy

Recent studies showcase that single-celled organisms, devoid of brains or neurons, can exhibit forms of advanced learning.

The most basic learning type is called habituation, where an organism gradually reduces its response to non-threatening stimuli like sounds or smells. This process is observed across various species, including animals and even plants. Habituation has also been demonstrated in some protists—complex eukaryotic cells that typically exist as unicellular organisms. For example, the trumpet-shaped blue spot stentor and slime mold poly skull.

Moving beyond habituation, associative learning evaluates how organisms connect multiple stimuli and predict events based on previous experiences. This concept was famously demonstrated by Ivan Pavlov, who showed that dogs could associate the sound of a bell with food, resulting in salivation at the mere sound.

Recently, Sam Gershman from Harvard University and his team utilized similar conditioning experiments to reveal that Stentor, a freshwater organism, is also capable of associative learning.

The stunning Stentor lives in freshwater habitats, using fine hair-like structures called cilia to navigate. Measuring up to 2 millimeters in length, it stands out among unicellular organisms. One end features a holdfast for surface attachment, while the opposite end has a trumpet-like feeding structure.


“When attached to a surface, Stentor primarily filters food from water. However, when disturbed, it retracts into a ball, making it temporarily unable to eat, which presents an ecological advantage,” Gershman notes.

To study Stentor’s learning capabilities, researchers conducted experiments by tapping the bottom of a Petri dish containing Stentor cultures. Most organisms initially contracted rapidly in response to loud taps, but this behavior diminished with repeated stimulation, indicating a form of habituation.

In subsequent experiments, the researchers introduced a weak tap followed by a strong tap. Typically, few microorganisms responded to the weak stimulus alone. However, the paired taps, executed every 45 seconds, gave Stentor sufficient time to re-extend, demonstrating associative learning over multiple trials.

After conducting over 10 trials, researchers noted an increased and then decreased probability of contraction following the weak tap, indicating a nuanced form of learning. “The observed pattern in the contraction rate signals a depth of cognitive ability previously underestimated in such simple organisms,” asserts Gershman.

The findings suggest that Stentor may be the first known protist capable of associative learning by linking weak and strong stimuli. “This raises compelling questions about the cognitive abilities of seemingly simple organisms compared to more complex multicellular entities,” adds Gershman.

Moreover, these revelations imply that associative learning could have ancient evolutionary roots, predating the emergence of complex nervous systems by millions of years. It echoes the way neurons in multicellular organisms learn through stimuli, drawing connections independent of synaptic changes, as described in previous research (here).

“The capacity of a single cell to perform complex tasks, once thought exclusive to organisms with brains, is quite remarkable,” concludes Shashank Shekhar of Emory University, who demonstrated Stentor’s ability to aggregate in short-lived groups for more efficient feeding.

“I suspect that other unicellular organisms may also possess similar associative learning capabilities,” he remarks. “Once such abilities arise, they may become prevalent across various organisms.”

While the mechanisms behind Stentor’s learning remain to be fully understood, Gershman posits that it may involve specific receptors allowing calcium influx, altering the internal voltage response to touch and thus influencing contraction behavior. Over time, repeated stimulation may modify these receptors, functioning as molecular switches to curtail contraction.

Topics:

  • Neuroscience /
  • Microbiology

Source: www.newscientist.com

Brain-free Learning: How Single-Celled Organisms Exhibit Pavlovian Conditioning

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Stentor coeruleus, a unique single-celled organism

Stentor coeruleus: A single-celled organism with remarkable learning capabilities

Melba Photo Agency / Alamy

Fascinatingly, simple, single-celled organisms like Stentor coeruleus demonstrate advanced learning abilities, despite lacking brains or neurons.

The most basic form of learning, termed habituation, entails a gradual decline in response to recurrent, harmless stimuli—such as specific smells or sounds. This phenomenon is prevalent across all animal species and even plants, having also been observed in protists—complex eukaryotic cells that are principally unicellular. For example, both the trumpet-shaped blue spot stentor and slime mold Poly skull exhibit this behavior.

Moreover, a more complex aspect of learning involves associating different stimuli and events, allowing organisms to predict relationships. This form of associative learning became widely notable through Ivan Pavlov’s experiments where dogs learned to associate a bell’s sound with feeding, leading to salivation upon hearing the sound alone.

Recently, Sam Gershman from Harvard University and his team conducted similar experiments that indicated Stentor is capable of associative learning.

These remarkable organisms inhabit ponds and swim utilizing cilia, tiny hair-like structures lining their bodies. Growing up to 2 millimeters in length, Stentor stands out among single-celled entities, with a holdfast for anchoring and a trumpet-shaped feeding apparatus.

According to Gershman, “When they’re attached, they filter food. If disturbed, they rapidly contract into a ball shape, becoming immobile and unable to eat—this behavior is ecologically advantageous.” Using this response, they explored Stentor’s learning potential by tapping the bottom of a Petri dish containing numerous Stentor cultures. Initially, the creatures contracted quickly, but as the tapping continued—totaling 60 taps every 45 seconds—the contractions reduced, indicating habituation.

Subsequently, a weak tap was introduced one second before the stronger tap. This association is rare in microorganisms; the paired taps occurred every 45 seconds to align with Stentor’s unfolding time.

After conducting over 10 trials, researchers observed that the likelihood of a contraction after the weak tap initially surged before declining. “We noted a notable peak where the contraction rate rose and then fell—this isolation wouldn’t be visible through weak taps alone,” Gershman explained.

The findings reveal that Stentor is the first protist recognized for its associative learning ability, linking weak taps with louder ones. “This raises intriguing questions about whether seemingly simple organisms possess cognitive abilities typically reserved for more intricate multicellular organisms with nervous systems,” Gershman asserted.

This insight suggests that the capability for associative learning has ancient evolutionary roots, predating multicellular nervous systems by hundreds of millions of years. Some parallels may still be present in human neuron behavior, exhibiting learning independent of synaptic changes, illustrating diverse learning mechanisms.

It’s remarkable that a single-celled organism can perform complex tasks previously attributed solely to beings with brains and neurons. Shashank Shekhar at Emory University notes that Stentor can aggregate into temporary groups for more efficient feeding.

Gershman suspects other unicellular organisms might also possess associative learning abilities. “Once this trait arises, it likely emerges in various forms,” he claims.

If an organism is capable of learning, it must somehow store memories. While the exact mechanism in Stentor remains unclear, Gershman postulates it may involve calcium-receptive mechanisms altering internal voltages in response to stimuli, leading to contractions. These adaptations suggest possible molecular switches that inhibit contraction following repeated stimuli.

Topics:

  • Neuroscience /
  • Microbiology

Source: www.newscientist.com

Biologists find ancient giant virus inserted into genome of a single-celled parasite

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Amoebidium appalachenseViruses in protists closely related to animals weave remnants of ancient giant viruses into their genetic code, according to a new study led by Queen Mary, University of London. The discovery sheds light on how complex organisms acquire parts of their genes and highlights the dynamic interplay between viruses and their hosts.

Amoebidium appalachense A unique model for understanding the hybrid origin of eukaryotic DNA. Image courtesy of Alex de Mendoza.

In this study, Dr. Alex de Mendoza Soler and his colleagues Amoebidium appalachense A unicellular parasite first isolated from the epidermis of a freshwater arthropod.

They found a surprising amount of genetic material from giant viruses, some of the largest known to science.

The sequences of these viruses are highly methylated, a chemical tag that often silences genes.

“It's like a hidden Trojan horse. Amoebidium appalachense It’s the DNA of,” says Dr. de Mendoza Soler.

“These viral insertions are potentially harmful, but Amoebidium appalachense It seems like we are suppressing them by chemically silencing them.”

The researchers then investigated how widespread this phenomenon may be.

They are some Amoebidium appalachense Examination of the isolates revealed wide variation in viral content.

This suggests that the processes of viral integration and silencing are continuous and dynamic.

“These findings call into question our understanding of viruses and the relationship between them and their hosts,” said Dr de Mendoza Soler.

“Traditionally, viruses are thought of as invaders, but this study suggests a more complex story.”

“Viral insertions may have played a role in the evolution of complex organisms by contributing new genes.”

“And this can be done by chemically controlling the invader's DNA.”

moreover, Amoebidium appalachense It shows intriguing parallels to how our own genomes interact with viruses.

It's similar to Amoebidium appalachense Humans and other mammals carry remnants of ancient viruses called endogenous retroviruses built into their DNA.

These remnants were previously thought to be inactive junk DNA, but now it appears some may be beneficial.

but, Amoebidium appalachense Endogenous retroviruses are much smaller, while the human genome is significantly larger.

Future studies can explore these similarities and differences to understand the intricate interactions between viruses and complex life forms.

Team Investigation result Published in today's journal Scientific advances.

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Luke A. Saleh others 2024. DNA methylation enables recurrent internalization of giant viruses in animal relatives. Scientific advances 10(28); Source: 10.1126/sciadv.ado6406

This article has been edited from an original release from Queen Mary, University of London.

Source: www.sci.news

Origami assists single-celled predator in elongating its ‘neck’

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Two micropipettes hold the organism and extend its “neck”

Elliot Flaum and Manu Prakash/Stanford University

Imagine if your neck could stretch long enough to reach your local store while sitting on the couch. That would be a human representation of what a single-celled predator can do. And now, a long-standing mystery has been solved: how that animal can stretch its “neck” to more than 30 times the length of its “body.”

The organism’s cell membrane is folded into a series of folds that can only unfold and fold in one direction. Elliot Flaum Stanford University and her colleagues Manu Prakash They found ways to stretch and fold the paper without it getting tangled. “Most of this came from just playing with paper,” Prakash says.

Lacrimaria Aurore It is a single-celled organism, or protist, that lives in freshwater and hunts prey with a highly extensible neck-like protrusion. Its name means “swan’s tears” after its swan-like neck and teardrop-shaped body.

The cell membrane is very flexible, but it is not elastic and does not stretch. L. Aurore Why their necks stretch so far has remained a mystery since they were first observed under a microscope in the 16th century. “Compared to a lot of other organisms, the neck stretches by an order of magnitude,” Prakash says. “That’s the mystery.”

He and Flaum L. Aurore To solve this mystery, samples taken from the swamp six or seven years ago were studied. Flaum used a variety of techniques to L. Aurore And inside that cytoskeleton is made up of structures called microtubules. “We looked at it in a variety of different ways to try to understand what was going on,” she says.

This means: L. Aurore It is folded into 15 pleats, with each pleat spiralling around the cell to form a helical structure, a folding pattern Prakash calls “curved crease origami,” or “lacrigami.”

but, L. Aurore How can such a vast region of the cell membrane unfold and fold without getting tangled? What Prakash and Flaum discovered is that because the pleats are stabilized by bands of microtubules connected to them, the entire fold cannot unfold at once. Instead, only a single point of the fold can unfold or fold at any one time.

As these points move in parallel along each of the 15 wrinkles, the cell membrane unfolds in an orderly fashion, lengthening the neck. Reversing this process shortens the neck.

“Instead of folding randomly like you would when crumpling a sheet of paper, it has guide rails that help you fold it the same way every time,” Flaum says.

The folding and unfolding of cells is driven by the beating of cilia that cover the entire surface of the cell, Prakash said. Unlike springs, cilia require energy to refold and unfold, whereas cell membranes bend easily and require very little energy.

As far as he knows, no one has discovered this origami technique before. “When I discovered this, I always assumed that someone playing with paper would have discovered this origami,” Prakash says. “It’s so easy.” He says anyone with paper and tape can make it.

“The neck’s ingenious origami-like design makes the cilia effective for high-speed, long-distance hunting,” they write. Leonardo Gordillo and Enrique Cerda At the University of Santiago in Chile Accompanying Articles“The origami-like protrusion mechanism identified by Flaum and Prakash has the potential to inspire new strategies in soft-matter engineering.”

In fact, Prakash and Flaum are currently working on developing a medical robot based on Rakurigami. “If you had a tiny microrobot in a very tight space, and it could suddenly stretch, that would be very useful for microsurgery,” he says. “But we did this research because it’s just beautiful and a mystery to solve. We didn’t expect it to be useful in any way.”

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Source: www.newscientist.com