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Examine the motility of swimming Euglena

Credit: Noselli et al.Some species of Euglenids, a diversified family of water-single-cellular organisms, can perform large amplitude, elegantly coordinated body deformations. Although this behavior has been known for centuries, its function is still highly debated. Scientists at the SISSA, the National Institute of Oceanography and Applied Geophysics (OGS), Scuola Superiore Sant & Anna and Universitat Politecnica de Catalunya have recently conducted a study of the motility of Euglena Gracilis, an Euglenid, especially in their response to containment . In his study, published in Nature Physics they examined the responses to swimming Euglena gracilis in environments with controlled congestion and geometry. "The great amplitude-coordinated movements of Euglena cells, called metabolism, have been described for centuries and still fascinate microbiologists, biophysics and amateur microscopists," Marino Arroyo, one of the researchers who conducted the study, told Phys .org. "We know that no other unicellular organism can move with such elegance and coordination. But how and why they do it is a mystery. Curiosity was what drove us to study Euglenaas motility." Amplitudes and Associated Body Deformations observed in Euglena are commonly referred to as "euglenoid movement" or "metabolism". Metabolism varies greatly between species and sometimes even within a species, ranging from rounding and gentle bending or twisting to periodic and highly coordinated peristaltic waves traveling along the cell body. "Among biophysics, metabolism was considered a way to swim in a fluid where these cells live," said Arroyo. "Protistologists, however, are not convinced of this function of metabolism because Euglena can swim very quickly…



Credit: Noselli et al.

Some species of Euglenids, a diversified family of water-single-cellular organisms, can perform large amplitude, elegantly coordinated body deformations. Although this behavior has been known for centuries, its function is still highly debated.

Scientists at the SISSA, the National Institute of Oceanography and Applied Geophysics (OGS), Scuola Superiore Sant & Anna and Universitat Politecnica de Catalunya have recently conducted a study of the motility of Euglena Gracilis, an Euglenid, especially in their response to containment . In his study, published in Nature Physics they examined the responses to swimming Euglena gracilis in environments with controlled congestion and geometry.

“The great amplitude-coordinated movements of Euglena cells, called metabolism, have been described for centuries and still fascinate microbiologists, biophysics and amateur microscopists,” Marino Arroyo, one of the researchers who conducted the study, told Phys .org. “We know that no other unicellular organism can move with such elegance and coordination. But how and why they do it is a mystery. Curiosity was what drove us to study Euglenaas motility.”

Amplitudes and Associated Body Deformations observed in Euglena are commonly referred to as “euglenoid movement” or “metabolism”. Metabolism varies greatly between species and sometimes even within a species, ranging from rounding and gentle bending or twisting to periodic and highly coordinated peristaltic waves traveling along the cell body.

“Among biophysics, metabolism was considered a way to swim in a fluid where these cells live,” said Arroyo. “Protistologists, however, are not convinced of this function of metabolism because Euglena can swim very quickly to beat his flagellum, as well as many other cell types. Instead, the predominant belief is that metabolism is a functionless vest” inherited “from ancestors who used cell body deformations to engulf We saw cells performing such a beautiful and coordinated dance, but we didn’t think it didn’t work, our study began as an attempt to support such a non-scientific feeling.

Diluted cultures of Euglena cells faint in generally using their flagellum and without changing their body shape, however, Arroyo and his colleagues observed that as time passed and the liquid under the microscope evaporated, their culture became more crowded and cells began to develop the metabolism.

“Inspired by these observations and amateur YouTube videos, we assumed that the cell deformations can be triggered by contact with other cells or boundaries in a tight environment. Under these conditions, the metabolism may be useful for crawling instead of swimming, “Antonio De Simone, another researcher involved in the study, told Phys.org.” Confirmation of this hypothesis was remarkably simple. As soon as we lightly pressed cells between two glass surfaces or drove them into thin capillaries, they began to systematically perform the metabolism, resulting in the fastest creep of any cell type, as far as we know, “added Giovanni Noselli, the first author of the study. [1

9659005] When they stopped testing this hypothesis, the researchers began to compare the creep behaviors observed in Euglena with the animal cells for which a large number of studies are currently available, previous studies have observed that animal cells crawling in a thin tube tend to push against their walls to move forward and overcome the resistance of the fluid in the tube. “We found that thanks to their peristaltic deformations, Euglena can either press on the walls or on the fluid to advance, making metabolism a remarkably robust, restricted movement”, said Simone. “They can actually move moving very little fly ie, a “smooth” propulsion mode, and they cannot be stopped even if the hydraulic resistance of the capillary is substantially increased. “In their experiments, Arroyo, De Simone, Noselli and their colleague Alfred Beran have noticed that Euglena cells could adapt to different degrees of childbirth. To perform this behavior, the cells can use a sensory system to detect their surrounding environment and some form of internal information processing to adjust their activity depending on the degree of capture.

The researchers found this explanation puzzling, however, especially seeing as Euglena is individual cells with no nervous system. To better understand how a single Euglena cell can control such an adaptable and robust locomotive mode, Arroyo and his colleagues modeled the moving device of Euglena cell, which is essentially a streaked cell casing.

“We wondered if their active envelopes, called a pellicle, responsible for the cell deformations, would mechanically adapt themselves to different mechanical conditions,” says Arroyo. “To investigate this, we developed a calculation model that shows that the correspondence between materials and molecular motors constituting Eugeneaas’ active envelopes could explain this adaptability, which in robotics is called mechanical or embodied intelligence. “

Arroyo and his colleagues gathered fascinating observations about body deformations of certain egg sides, suggesting that this behavior may in some cases be triggered by childbirth. show a function of metabolism, its study established a new category of cell robots, which are particularly fast, robust and adaptable. “” If crawling through metabolism is so beneficial, one might wonder why it is not conserved among other species, “said Arroyo. “The answer is that it requires an intricate mask in, the pellet, which is a streaky casing made of elastic strips coupled by molecular motors. This selectively deformable surface lies somewhere the rigid wall of the plant cell and the liquid envelope of animal cells. biology, we believe that the underlying physical / geometric principles that enable shape changes of this envelope can be applied to artificial systems constructed, for example in soft robotics. “

The calculation model developed by Arroyo and his colleagues was finally able to emphasize the function of widely documented euglenoid movements. Their results indicate that the walking ability of these organisms does not require specific mechanosensitive feedback, but can be explained by mechanical self-regulation of an elastic and extended motor system. [19659005] In their latest study, researchers successfully identified a function and operating principles behind the adaptable body deformation of Euglena cells, and are now planning to further investigate the cellular mechanisms by which metabolism is triggered and which cellular deformations are propagated.

“We plan to investigate metabolism across different species of Euglena, “said DeSimone.” Initial observations reveal different flavors of metabolism. We also work on building artificial materials and devices inspired by the Euglena cells’ active and deformable envelopes “.


Explore further:
Pond dwellers called Euglena swim in polygons to avoid light

More information:
Giovanni Noselli et al. Swimming Euglena responds to framing with a behavioral change that allows for effective crawling, Nature Physics (2019). DOI: 10.1038 / s41567-019-0425-8 https://www.nature.com/articles/s41567-019-0425-8

Journal reference:
nature Physics

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