Single cell organism's brain

Multi cellular organisms have brain.But what about single celled organisms do they have brain to control the cell's work?If they have something what that part called?You can say that the nucleolus do that work then all cells have nucleolus.Then why multi cellular organisms have brain?

Single cells do not have brains. Plenty of multicellular organisms do not have brains either. Multicellular organisms such as fungi, plants, sponges do not even have nervous systems, and many organisms with nervous systems (like some jellyfish, molluscs, arthropods… ) do not have something you could call a brain (I mean, I guess arthropods have a brain in that it's how you call the ganglion they have in the head, but it's not always that much bigger than other ganglia).

Organisms do not actually need a centralized control to function. You can do a lot in a multicellular organism simply with cellular signalling (each cells reacts to its environment in certain ways, sometimes emitting molecules that cause other cells to react in certain ways and so on), and single cells work similarly inside themselves, different parts of the cell "work together" by producing or consuming chemicals that others react to (or other physical processes).

Brains (i.e. a centralization of the nervous system) allow more complex behavior, to coordinate perceptions and actions in more precise and flexible ways.

This Wikipedia article on Chemotaxis for example describes how cells can move along a gradient of a useful or dangerous chemical, and gives some of the molecular mechanisms for this to happen:

Here is an article that seems to describe cell signalling in some detail:

I think you have misconceived what a brain actually means. A brain is an organ, which is very different from the organelles of microorganisms.

Organ: a collection of cells that carry out a specific function. Organelle: a structure enclosed in a membranne that exists in the cytoplasm of a cell.

The brain is a collection of neurons, of sometimes just cells that respond to stimuli. Therefore, a unicellular organism does not have a brain. All they have are organelles.

How do unicellular organisms respond to stimuli then?

On the surface of the cell membrane are proteins (receptors). When a receptor is activated i.e. a molecule binds to it, it will set of a signalling cascade (think of a waterfall, or domino). This cascade which consists of other enzymes will ultimately end with the desired enzyme being activated and it catalyzes a desired reaction.

That is how cells react to stimuli. Strickly speaking, they do not have brains, but they can make decisions, they are forced to make a decision (they cannot make a choice, if a signalling molecule is present it will activate a pathway, it must unless another molecule regulates it).

Single cell organism's brain - Biology

Organism-level systems biology aims to identify, analyze, control and design cellular circuits in organisms. Many experimental and computational approaches have been developed over the years to allow us to conduct these studies. Some of the most powerful methods are based on using optical imaging in combination with fluorescent labeling, and for those one of the long-standing stumbling blocks has been tissue opacity. Recently, the solutions to this problem have started to emerge based on whole-body and whole-organ clearing techniques that employ innovative tissue-clearing chemistry. Here, we review these advancements and discuss how combining new clearing techniques with high-performing fluorescent proteins or small molecule tags, rapid volume imaging and efficient image informatics is resulting in comprehensive and quantitative organ-wide, single-cell resolution experimental data. These technologies are starting to yield information on connectivity and dynamics in cellular circuits at unprecedented resolution, and bring us closer to system-level understanding of physiology and diseases of complex mammalian systems.

Single-Celled Organisms Have No Brains But Some Still Appear To Change Their Minds

Some single-celled organisms are capable of adopting a hierarchical response to environmental conditions, trying certain options only when others have been found to fail. The observations vindicate claims that have been mocked for more than a century, and demonstrate the capacity for autonomy to exist even without cells specialized for thinking.

A century ago, Herbert Spencer Jennings described the single-celled protist Stentor roeseli's response to unpleasant stimuli. S. roeseli usually attaches itself to algae and beats its cilia to bring food particles close enough to consume. Jennings reported that when exposed to an infusion of carmine powder, S. roeseli will usually bend out of the way of the noxious stream, as if hoping it will quickly pass and things will return to normal.

However, when he repeatedly applied the same chemical, Jennings found the protist would try alternative approaches, either reversing the direction in which the cilia beat to repel what was troubling it or either contraction or detachment. In the last case, the protist would float off to seek some more attractive perch.

For humans, or even advanced animals, this sequence looks normal, with minimal responses that escalate only if necessary. It's much more unexpected in something lacking a central nervous system. How does something without a brain develop a memory, let alone the capacity to apparently “decide” the threat is ongoing enough to require relocation?

Jennings' account was consequently met with skepticism, and when others failed to replicate his work, it was dismissed. Yet 70 years after his death, Jennings has been vindicated.

In Current Biology, a team led by Harvard's Dr Jeremy Gunawardena describe firing sodium azide-carrying polystyrene beads at some S. roeseli under a microscope and recording the response. Video evidence of exactly the sequence Jennings described is there for all to see – first evasion, then attempts to repel the threat, and finally contraction or escape when it was clear the balls were not going away.

"We consider the behavior hierarchy as a form of sequential decision making," the paper notes, "in the sense that, when given similar stimulation repeatedly, the organism 'changes its mind' about which response to give."

Gunawardena thinks the reason those who sought to replicate Jennings failed was that they were using a different and more mobile species of Stentor, having not been able to get hold of S. roeseli. Nevertheless, the authors acknowledge not all the S. roeseli exposed to the bead bombardment followed the neat order Jennings described. On a group basis, this pattern was typical, but many specimens opted to try to beat away the balls as their first option.

The mystery of how some single-celled organisms can change their minds in response to new information is only matched by the puzzle of why so many people apparently refuse to do the same.

When the trumpet-shaped single-celled organism Stentor roeseli experiences something noxious, it has several responses, which it tries in order, moving from the least disruptive to those that involve more sacrifice. Dexter et al./Current Biology

Memory Without a Brain: How a Single Cell Slime Mold Makes Smart Decisions

Having a memory of past events enables us to make smarter decisions about the future. Researchers at the Max-Planck Institute for Dynamics and Self-Organization (MPI-DS) and the Technical University of Munich (TUM) have now identified how the slime mold Physarum polycephalum saves memories – although it has no nervous system.

The ability to store and recover information gives an organism a clear advantage when searching for food or avoiding harmful environments. Traditionally it has been attributed to organisms that have a nervous system.

A new study authored by Mirna Kramar (MPI-DS) and Prof. Karen Alim (TUM and MPI-DS) challenges this view by uncovering the surprising abilities of a highly dynamic, single-celled organism to store and retrieve information about its environment.

Window to the past

The slime mold Physarum polycephalum has been puzzling researchers for many decades. Existing at the crossroads between the kingdoms of animals, plants and fungi, this unique organism provides insight into the early evolutionary history of eukaryotes – to which also humans belong.

Prof. Karen Alim, Technical University of Munich, and Mirna Kramar, Max-Planck Institute for Dynamics and Self-Organization, discovered how the slime mold Physarum polycephalum weaves its memories of food encounters directly into the architecture of the network-like body and uses the stored information when making future decisions. Credit: Bilderfest / TUM

Its body is a giant single cell made up of interconnected tubes that form intricate networks. This single amoeba-like cell may stretch several centimeters or even meters, featuring as the largest cell on earth in the Guinness Book of World Records.

The network architecture as a memory

“It is very exciting when a project develops from a simple experimental observation,” says Karen Alim, head of the Biological Physics and Morphogenesis group at the MPI-DS in Göttingen and professor for the Theory of Biological Networks at the Technical University of Munich.

When the researchers followed the migration and feeding process of the organism and observed a distinct imprint of a food source on the pattern of thicker and thinner tubes of the network long after feeding.

The slime mold Physarum polycephalum consists of a single biological cell. Because of his ingenious ability to adapt his tubular network to a changing environment, he has been called “intelligent”. Researchers at TUM and MPI-DS have now found out how it stores information – even without having a nervous system or a brain. Credit: Nico Schramma / MPI-DS

“Given P. polycephalum’s highly dynamic network reorganization, the persistence of this imprint sparked the idea that the network architecture itself could serve as memory of the past,” says Karen Alim. However, they first needed to explain the mechanism behind the imprint formation.

Decisions are guided by memories

For this purpose the researchers combined microscopic observations of the adaption of the tubular network with theoretical modeling. An encounter with food triggers the release of a chemical that travels from the location where food was found throughout the organism and softens the tubes in the network, making the whole organism reorient its migration towards the food.

“The gradual softening is where the existing imprints of previous food sources come into play and where information is stored and retrieved,” says first author Mirna Kramar. “Past feeding events are embedded in the hierarchy of tube diameters, specifically in the arrangement of thick and thin tubes in the network.”

“For the softening chemical that is now transported, the thick tubes in the network act as highways in traffic networks, enabling quick transport across the whole organism,” adds Mirna Kramar. “Previous encounters imprinted in the network architecture thus weigh into the decision about the future direction of migration.”

Design based on universal principles

“Given the simplicity of this living network, the ability of Physarum to form memories is intriguing. It is remarkable that the organism relies on such a simple mechanism and yet controls it in such a fine-tuned manner,” says Karen Alim.

“These results present an important piece of the puzzle in understanding the behavior of this ancient organism and at the same time points to universal principles underlying behavior. We envision potential applications of our findings in designing smart materials and building soft robots that navigate through complex environments,” concludes Karen Alim.

Reference: “Encoding memory in tube diameter hierarchy of living flow network” by Mirna Kramar and Karen Alim, 23 February 2021, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2007815118

Can a single-celled organism 'change its mind'? New study says yes

A sketch of avoidance hierarchy in S. roeseli based on Jennings' original descriptions. Credit: Dexter et al. & Current Biology

Once, single-cell life claimed sole dominion over the earth. For some three billion years, unfathomable generations of unicellular organisms ate, grew and reproduced among only each other. They evolved into predators and prey, thrived and spread across the primordial waters and land, and formed complex and dynamic ecosystems in every ecological niche on the planet. Around 600 million years ago, some even crossed the threshold into multicellularity.

Today, however, single-cell organisms are synonymous with notions like primitive and simple. Yet, new research suggests that they may be capable of much more than their very distant human cousins might suspect.

In an effort to replicate an experiment conducted over a century ago, systems biologists at Harvard Medical School now present compelling evidence confirming at least one single-cell organism—the strikingly trumpet-shaped Stentor roeselii—exhibits a hierarchy of avoidance behaviors.

Exposed repeatedly to the same stimulation—in this case a pulse of irritating particles—the organism can in effect "change its mind" about how to respond, the authors said, indicating a capacity for relatively complex decision-making processes.

The results are published online in Current Biology on Dec. 5.

"Our findings show that single cells can be much more sophisticated than we generally give them credit for," said corresponding study author Jeremy Gunawardena, associate professor of systems biology in the Blavatnik Institute at HMS.

The researchers say such sophistication makes evolutionary sense.

"Organisms like S. roeselii were apex predators prior to multicellular life, and they are extremely widespread in many different aquatic environments," he said. "They have to be 'clever' at figuring out what to avoid, where to eat and all the other things that organisms have to do to live. I think it's clear that they can have complex ways of doing so."

A complex hierarchy of avoidance behaviors in a single-celled freshwater protist, Stentor roeseli. Credit: Dexter et al., Current Biology

Fascinating yet forgotten

A decade ago, at a lecture by the English biologist Dennis Bray, Gunawardena was introduced to the work of the prominent American zoologist Herbert Spencer Jennings, who, in 1906, published the influential text Behavior of the Lower Organisms. One particular experiment caught Gunawardena's eye.

Jennings was studying S. roeselii, a member of a widespread genus of freshwater protist. These single cells are notable for their relatively large size and unique trumpet-shaped bodies. Their surfaces and trumpet "bells" are lined with hairlike projections called cilia, used to swim and to generate a vortex in the surrounding fluid, which sweeps food into their "mouths." At the other end of their bodies, they secrete a holdfast, which attaches them to detritus to stay stationary while feeding.

With a microscope, a pipette and a steady hand, Jennings meticulously documented the behavior of S. roeselii when exposed to an environmental irritant in the form of carmine powder.

Jennings observed an ordered series of behaviors. He noted that, typically, S. roeselii would repeatedly bend its body to avoid the powder. If irritation persisted, it would reverse the movement of its cilia to expel particles away from its mouth. If this too failed, it would then contract, swiftly pulling itself down onto its holdfast like a barnacle retreating into its shell. Finally, if all prior efforts failed, S. roeselii would detach its holdfast and swim away.

These behaviors formed a hierarchy, an escalation of actions that the organism carried out based on a ranked preference. This observation suggested that it possessed some of the most complex behaviors known for a single cell with a single nucleus.

The experiment drew widespread interest, but subsequent efforts to replicate it—in particular, a study published in 1967—were unsuccessful. As a result, Jennings' findings were largely discredited and forgotten by modern science.

Like carmine powder in an otherwise perfectly habitable puddle of water, this bothered Gunawardena, so he tracked down the 1967 study. To his astonishment, he found that the authors, who were unable to find S. roeselii, had used a different species to replicate Jennings' experiment—Stentor coeruleus, which prefers to swim instead of attaching to feed.

Little surprise, then, that they failed to reproduce the results, Gunawardena thought. He became infatuated with trying to accurately replicate Jennings' experiment. But as a mathematician by training running a medical school lab focused on molecular information processing, he found it difficult to convince others.

"I kept bringing up this idea at my lab group meeting, saying that it tells us something about the capabilities of single cells. We don't think this way about how cells work anymore," he said. "And, unsurprisingly, no one was interested. It's ancient history, it's descriptive biology—all the things young, bright trainees wouldn't touch."

But he persisted. One of his postdoctoral fellows, Sudhakaran Prabakaran, now a group leader at the University of Cambridge in England, became interested. And around eight years ago, Joseph Dexter, an undergraduate intern who later became Gunawardena's Ph.D. student and who is now a fellow at the Neukom Institute for Computational Science at Dartmouth, was also attracted to the idea.

Driven only by an irrepressible sense of curiosity and history, with no formal grant support, the three engaged in a years-long side project.

"It was a completely off-the-books, skunkworks project," Gunawardena said. "It wasn't anyone's day job."

Dexter and Prabakaran designed and undertook the experiments, and their first challenge was finding S. roeselii. They hunted everywhere, even searching in local ponds. Ultimately, they located a supplier in England, which sourced the organisms from a golf course pond and shipped them across the Atlantic.

The team set up an experimental apparatus equipped with video microscopy and a micropositioning system to accurately deliver an irritant near the mouth of their S. roeselii test subjects. They initially used carmine powder but saw little response, and through trial and error, found that microscopic plastic beads were effective.

To their delight, the trio succeeded in eliciting—and reproducing—all the behaviors that Jennings once described.

However, they did not see the neat, orderly hierarchy of behaviors that Jennings had documented. Rather, there seemed to be considerable variation among subjects—one specimen might bend and alter its cilia before contracting, but another might only contract repeatedly, while another would alternate bending and contracting.

So, the three fell back on their core expertise as quantitative biologists. They developed a method to encode the different behaviors they saw into a series of symbols, and then used statistical analyses to look for patterns.

Where observation failed, math triumphed. There was, indeed, a behavioral hierarchy, the analysis revealed. When faced with an irritant, S. roeselii will, most of the time, begin by bending and altering its cilia, often simultaneously. If the irritation continues, it will then contract or detach and swim away. The latter behaviors almost always occur after the former, and organisms never detach without first contracting, indicating a preferred order of actions.

"They do the simple things first, but if you keep stimulating, they 'decide' to try something else. S. roeselii has no brain, but there seems to be some mechanism that, in effect, lets it 'change its mind' once it feels like the irritation has gone on too long," Gunawardena said.

"This hierarchy gives a vivid sense of some form of relatively complex, decision-making calculation going on inside the organism, weighing whether it's better to execute one behavior versus another," he said.

In successfully replicating Jennings' experiment and illuminating new quantitative observations about the behavioral capabilities of S. roeselii, the team hopes it has resolved the historical confusion about the accuracy of his findings.

But the results now raise numerous new questions.

The analyses showed that there is almost a perfectly even chance that any individual S. roeselii will choose to contract or detach, a clue that is particularly tantalizing to scientists who study how cells process information at the molecular level. The decision between the two behaviors is consistent, with each organism independently flipping an unbiased coin, regardless of previous actions, the authors said.

"It's somehow basing its decisions, at the molecular level, on a fair coin toss," Gunawardena said. "I can't think of any known mechanism that would allow them to implement this. It's incredibly fascinating and something Jennings never observed because we needed quantitative measurements to reveal it."

More broadly, the authors say, the observation that single cells can be capable of complex behaviors could inform other areas of biology.

In developmental biology or cancer research, for example, the processes cells undergo are often referred to as programs, Gunawardena said, suggesting that cells are "programmed" to do what they do. "But cells exist in a very complex ecosystem, and they are, in a way, talking and negotiating with each other, responding to signals and making decisions."

"I think this experiment forces us to think about the existence of, very speculatively, some form of cellular 'cognition,' in which single cells can be capable of complex information processing and decision-making in response," he continued. "All life has the same underpinnings, and our results give us at least one piece of evidence for why we should be broadening our view to include this kind of thinking in modern biology research."

"It also illustrates how, sometimes, we tend to ignore things not because they don't exist, but because we don't think it's important to look at them," he added. "I think that's what makes this study so interesting."

Whole-body and Whole-Organ Clearing and Imaging Techniques with Single-Cell Resolution: Toward Organism-Level Systems Biology in Mammals

Organism-level systems biology aims to identify, analyze, control and design cellular circuits in organisms. Many experimental and computational approaches have been developed over the years to allow us to conduct these studies. Some of the most powerful methods are based on using optical imaging in combination with fluorescent labeling, and for those one of the long-standing stumbling blocks has been tissue opacity. Recently, the solutions to this problem have started to emerge based on whole-body and whole-organ clearing techniques that employ innovative tissue-clearing chemistry. Here, we review these advancements and discuss how combining new clearing techniques with high-performing fluorescent proteins or small molecule tags, rapid volume imaging and efficient image informatics is resulting in comprehensive and quantitative organ-wide, single-cell resolution experimental data. These technologies are starting to yield information on connectivity and dynamics in cellular circuits at unprecedented resolution, and bring us closer to system-level understanding of physiology and diseases of complex mammalian systems.

Single-Cell Analyses Identify Brain Mural Cells Expressing CD19 as Potential Off-Tumor Targets for CAR-T Immunotherapies

CD19-directed immunotherapies are clinically effective for treating B cell malignancies but also cause a high incidence of neurotoxicity. A subset of patients treated with chimeric antigen receptor (CAR) T cells or bispecific T cell engager (BiTE) antibodies display severe neurotoxicity, including fatal cerebral edema associated with T cell infiltration into the brain. Here, we report that mural cells, which surround the endothelium and are critical for blood-brain-barrier integrity, express CD19. We identify CD19 expression in brain mural cells using single-cell RNA sequencing data and confirm perivascular staining at the protein level. CD19 expression in the brain begins early in development alongside the emergence of mural cell lineages and persists throughout adulthood across brain regions. Mouse mural cells demonstrate lower levels of Cd19 expression, suggesting limitations in preclinical animal models of neurotoxicity. These data suggest an on-target mechanism for neurotoxicity in CD19-directed therapies and highlight the utility of human single-cell atlases for designing immunotherapies.

Can a Cell Make Decisions?

In 1906, zoologist Herbert Spencer Jennings published Behavior of the Lower Organisms, a book that contained a provocative idea: microbes can change their minds.

His subject was a single cell bristling with beating hairs called Stentor. These trumpet-shaped predators are so large fish can eat them and humans can see them, and so brazen they can catch and eat rotifers&mdashproper animals with hundreds of cells and a simple brain. In the microbial galaxy, stentors lie somewhere between Star Destroyer and sarlacc pit.

Jennings decided to annoy it and see what happened. When confronted with a stream of irritating carmine powder expertly aimed at their mouths by his steady hand, Stentor would first bend away, then reverse the beating of its hairs (called cilia) to expel the powder, then contract and finally detach.

He noted that the order of behaviors varied somewhat with different stimuli (he tried other chemicals) and steps were sometimes omitted. &ldquoBut it remains true,&rdquo he wrote, &ldquothat under conditions which gradually interfere with the normal activities of the organism, the behavior consists in &lsquotrying&rsquo successively different reactions, till one is found that affords relief.&rdquo

In short, stentors could confront a stimulus with one behavior, and then choose a costlier approach if the irritant persisted. At least for a short while (a period that Jennings declared difficult to determine experimentally and still unresolved), it could &ldquoremember&rdquo that it had tried one solution without success, and opt for another.

But in 1967, scientists from a different school of animal behavior repeated his experiment and failed to produce the same result. And with that, Jennings&rsquos findings were consigned to the dustbin.

Then about 10 years ago, Jeremy Gunawardena, an associate professor of systems biology at Harvard Medical School, discovered the experiment and its defenestration and decided that it deserved another look. To his surprise, he discovered the 1967 team had not used the correct species of Stentor (being behaviorists who believed variation flowed from the environment and not genes, they might have felt the species didn&rsquot matter). The one they had chosen, Stentor coeruleus, strongly prefers to swim, unlike Jennings&rsquos Stentor roeselii, which prefers to chill poolside.

Gunawardena became fascinated by what replicating the experiment might reveal about what single cells are capable of. After years of dangling the idea fruitlessly at lab meetings, he found undergrad Joseph Dexter and postdoc Sudhakaran Prabakaran were willing to give it a try at night and on weekends&mdashwith no funding.

This time, the Harvard team managed to track down the correct species in an English golf course pond, construct their own &ldquoDevice for Irritating Stentors&rdquo (being quantitative biologists, they lacked Jennings&rsquos extreme pipette skills), and discovered something extraordinary.

In their setup, Stentor did not respond to carmine powder the way Jennings described. However, when faced with barrages of 21st-century plastic microbeads, individual Stentor roeseli behaved consistent with Jennings&rsquos description&mdashand in one remarkable way that Jennings did not observe in 1906.

If Stentor really can &ldquodecide,&rdquo it certainly isn&rsquot the only way the ciliates&mdashthe group of shaggy microbes to which Stentor belongs&mdashresemble us. A ciliate operates like an animal at the scale of a single huge cell, and the resemblance can be startling.

For example, some glue bundles of their cilia into structures called cirri and can use them as legs, mouths, paddles or teeth. Euplotes skitters nimbly along surfaces atop cirri like some sort of Close Encounters&ndashclass water flea. The cirri are wired by nervelike neurofibrils. If the fibrils are cut, the cirri fall limp.

Some ciliates pack tiny tethered darts they can fire to attack prey, deter predators or simply drop anchor. Others sport tentacles that snag food. Like sea stars, ciliates can regenerate entire bodies within a day or two from shockingly tiny pieces provided those pieces contain both a bit of the cell&rsquos cilia-studded armor and a bit of nucleus, the cell&rsquos genetic heart. Many ciliates divide in the usual way by pinching in two, but some stalked or sessile ciliates push small round larvae into the world through a special birth canal.

One ciliate called Diplodinium lives in the rumen of cows and other hoofed animals, a special environment known to harbor all kinds of strange things, about half of which by mass may be ciliates (think about that next time you see a cow placidly chewing its cud). Diplodinium contains neurofibrils, cirri, musclelike striated contractile fibers called myonemes, a &ldquobackbone&rdquo made of stacked plates, a mouth, an esophagus that contracts with the help of a ring tethered to its exterior, and an anus. But remember: single cell.

In short, ciliates have taken the biology of the solo cell to its apparent earthly limit. Having something like a noggin in there is less credulity-stretching once you grasp this.

In the new study, published in the journal Current Biology in 2019, the scientists found that Stentor indeed switched behaviors in response to repeated puffs of beads, and the order of operations was generally consistent with Jennings&rsquos description. Detachment was always preceded by contraction, and mathematical analyses revealed cilia alternation or bending were far more likely to appear before contraction than after.

There is something else interesting about their data , which I en courage you to examine for yourself: it sure looks like stentors have personalities. Some repeatedly contracted and relaxed, or bent, contracted, then relaxed, seemingly willing to tolerate irritation&mdashor to live dangerously. These were the optimists.

Some contracted once or just a few times, never to relax again. Others contracted and detached, and that was it. These were the pessimists (or perhaps just the ones with a more recent successful &ldquodoor dash&rdquo).

Some stentors always responded with one or two preferred behaviors, and never with others that they were surely just as biologically capable of performing. One indefatigable individual subjected to 13 bead blasts responded persistently with ciliary alternation or contraction, never bending or detachment.

Does Stentor possess something like agency&mdasha capacity to make decisions? This study and Jennings&rsquo evidence certainly suggest so.

There was a final provocative finding. This team's statistical analysis revealed that the choice between contracting or detaching was consistent the probability of a fair coin toss. In other words, it seemed perfectly random.

There&rsquos only one problem: no known cellular mechanism can produce this result. That head scratcher remains both unreplicated and unexplained.

Perhaps it is time to let go of our preconceived notions of what cells are capable of because they are only cells, and the cells in our own soviet-style bodies are the equivalent of worker bees. The capabilities of wily, gunslinging, free-living cells may well exceed our dim primate imaginations.


Jennifer Frazer, an AAAS Science Journalism Award–winning science writer, authored The Artful Amoeba blog for Scientific American. She has degrees in biology, plant pathology and science writing.

Authors’ contributions

JQW, HW, and RCDD conceived the project and participated in writing the manuscript. RCDD designed the figures. All authors read and approved the final manuscript.


The authors would like to thank Dr. Eva M. Zsigmond for editing the manuscript.

Competing interests

The authors declare that they have no competing interests.


JQW, HW, and RCDD were supported by grants from the National Institutes of Health R01s NS088353 and NS091759 the Staman Ogilvie Fund-Memorial Hermann Foundation the UTHealth BRAIN Initiative and CTSA UL1 TR000371 and a grant from the University of Texas System Neuroscience and Neurotechnology Research Institute (Grant #362469).

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Scientists Find Single-Celled Microorganisms in Deep, Hot Subseafloor Sediments

An international team of researchers has discovered microbial life, in particular bacterial vegetative cells, in up to 1.2-km-deep and up to 120 degrees Celsius hot sediments in the Nankai Trough subduction zone off Cape Muroto, Japan.

A microbial cell (center of the picture) detected from a sediment core sample at the depth of 1176.8 m at 120 degrees Celsius. Scale bar – 20 μm. Image credit: JAMSTEC / IODP.

“Water boils on the (Earth’s) surface at 100 degrees Celsius, and we found organisms living in sediments at 120 degrees Celsius,” said team member Dr. Arthur Spivack, a scientist in the Graduate School of Oceanography at the University of Rhode Island.

In October 2020, a team of researchers announced that microbial diversity below the seafloor is as rich as on Earth’s surface.

They discovered 40,000 different types of microorganisms from core samples from 40 sites around the globe.

Dr. Spivack and colleagues focused on the Nankai Trough off the coast of Japan, where the deep-sea scientific vessel, Chinkyu, drilled a hole 1,180 m deep to reach sediment at 120 degrees Celsius.

“Only a few scientific drilling sites have yet reached depths where temperatures in the sediments are greater than 30 degrees Celsius,” said Professor Kai-Uwe Hinrichs, a researcher in the Center for Marine and Environmental Sciences (MARUM) at the University of Bremen.

“The goal of the T-Limit Expedition, therefore, was to drill a thousand-meter deep hole into sediments with a temperature of up to 120 degrees Celsius — and we succeeded.”

“Surprisingly, the microbial population density collapsed at a temperature of only about 45 degrees Celsius,” said Dr. Fumio Inagaki, a researcher in the Research and Development Center for Ocean Drilling Science and Kochi Institute for Core Sample Research at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC).

“It is fascinating — in the high-temperature ocean floor, there are broad depth intervals that are almost lifeless.”

“But then we were able to detect cells and microbial activity again in deeper, even hotter zones — up to a temperature of 120 degrees Celsius.”

While the concentration of vegetative cells decreases sharply to a level of less than 100 cells per cm 3 of sediment at over 50 degrees Celsius, the concentration of endospores increases rapidly and reaches a peak at 85 degrees Celsius.

Endospores are dormant cells of certain types of bacteria that can reactivate and switch to a live state whenever conditions are favorable again.

“Some specialist types are able to adapt to these severe conditions and persist over geological time spans in a sort of deep sleep,” Dr. Inagaki said.

“The findings of our expedition are surprising,” said Dr. Verena Heuer, a researcher of MARUM.

“They show that at the lower boundary of the biosphere lethal limits coexist with opportunities for survival. We didn’t expect that.”

“And this new understanding would not have been possible without the strong interdisciplinary team and its dedicated spirit of cooperation.”

“We found chemical evidence of the organisms’ use of organic material in the sediment that allows them to survive,” Dr. Spivack said.

“This research tells us that deep sediment is habitable in places that we did think possible.”

While this is exciting news on its own, the research could point to the possibility of life in harsh environments on other planets.

“Like the search for life in outer space, determining the limits of life on the Earth is fraught with great technological challenges,” the scientists said.

Ta, Os, Rh are metals in the periodic table. Metal are chemical substances that share electrons to gain stability. They are good conductors and pass electricity and heat when they are used as conductors. Metals will shine when they are freshly prepared, polished, or fractured. Ta, Os, Rh Metals: Interestingly, these three metals (Ta … Read more

Q. In the liver, detoxifying enzymes are localized in what organelle? 1) Lysosomes 2) Nucleolus 3) Mitochondria 4) Golgi apparatus 5) Smooth endoplasmic reticulum 6) Rough endoplasmic reticulum 7) Peroxisomes Answer: 5) Smooth endoplasmic reticulum Explanation: The enzymes of the smooth endoplasmic reticulum in the liver cells of vertebrates help in detoxifying toxic … Read more