Katherine Ralston
Katherine Ralston

Caught on Camera: An Amoeba Eating Human Cells Alive

Katherine Ralston
Katherine Ralston

Are you squeamish? Does the thought of germs and/or microscopic organisms give you the creeps? You might want to turn back now.

The Entamoeba histolytica amoeba infects 50 million people all over the world, and every year, it kills roughly 100,000 of them. Until recently, researchers weren’t sure how this microbe worked. Now, thanks to postdoctoral researcher Katherine Ralston and her team at the University of Virginia in Charlottesville, we have some unsettling insight into how the amoeba attacks its victims: It eats their cells, bit by bit, until the cells are dead.

This particular infection occurs most commonly in developing nations, after victims ingest contaminated food or water. In some parts of Bangladesh, for example, Ralston says 30 percent of children contract the amoeba at least once before their first birthday. While some victims show no symptoms at all, in others, it can cause severe dysentery and even spread to other organs—like the liver—which can be deadly. So, researchers wanted to know: What exactly happens after these microbes are ingested? How do they go on to cause disease in other parts of the body?

To get an up-close look at the action, researchers, led by Virginia’s William Petri, Jr., mixed the amoeba with human cells and observed its behavior under a microscope. Like a microscopic Pacman, almost immediately upon contact, the parasite started taking bites of and ingesting the human cells. Within about 10 minutes, the cells met their untimely death, and the amoeba moved on to its next victim. Researchers caught the whole thing on video.

Why is this process so shocking? Aside from the cringeworthy fact that a parasite is slowly eating human cells alive, researchers were also surprised because many other microbes take a somewhat less violent approach to eliminating cells, emitting something toxic to poison them. “It was thought they would kill cells like a lot of other microbes kill cells,” Ralston told mental_floss. “Instead you see them gnawing on the cell. This really physical cell death is not typical.”

Even more puzzling: The parasite isn’t using the human cells as a primary source of nourishment. “Once these cells had been killed, they stopped eating and moved on to a new cell,” Ralston says. “If it was about nutrition, they would ingest the rest of the cell as a readily available meal.” So why go through the trouble of ingesting the cells, if not for nourishment? Ralston and her team think this is a way for the parasite to invade the intestine, or perhaps a defense mechanism against immune cells sent to rescue the victim from the parasite.

But researchers needed to be sure that this gnawing process is what actually kills the cells. Could cells survive if they’d only been bitten once or twice? If they knew the cause of cell death, they could move forward developing treatments to prevent it. So they altered the microbe, inhibiting its ability to attach to the cells, and saw that indeed, the cells can endure the carnage, up to a point. “We actually found that with some inhibitors—even if we didn’t completely inhibit nibbling, just reduced it—that it allowed the human cells to live,” Ralston says. “It seems there’s a threshold. If we could block this process, that would be a potential new therapy.”

The findings appear in the April edition of the journal Nature and could lead to new treatments for Entamoeba histolytica, which is currently treatable with one class of drugs. “This changes the paradigm for this infection, “ Ralston says.

Live confocal microscopy time lapse demonstrating that bites of human cell material are internalized by the amoebae. Ingestion of bites occurs while human Jurkat cells are viable and ceases once they are dead. Human cells were pre-labeled with DiI (red; cell membrane), Flou4 (green; intracellular Ca2+); and SYTOX blue (blue; nucleic acid in permeable cells) was present in the media during imaging. Images were collected every 30 seconds and are played back at 1 frame per second

Live confocal microscopy time lapse demonstrating that human cell intracellular calcium elevation follows the ingestion of bites. Human Jurkat cells were pre-labeled with DiD (pink; cell membrane), and Flou4 (green; intracellular Ca2+). Images were collected every 20 seconds and are played back at 1 frame per second.

Public Domain, Wikimedia Commons
13 Electrifying Nikola Tesla Quotes
Public Domain, Wikimedia Commons
Public Domain, Wikimedia Commons

The greatest geek who ever lived had more than just science on the brain. While he was alive, Nikola Tesla’s advancements were frequently and famously attributed to others. But history has shown us the magnitude of his work, a sentiment best expressed by Fiorello LaGuardia’s eulogy: “Tesla is not really dead. Only his poor wasted body has been stilled. The real, the important part of Tesla lives in his achievement which is great, almost beyond calculation, an integral part of our civilization, of our daily lives.” Here are 13 electric quotes from the legendary scientist/engineer/inventor.


“... The female mind has demonstrated a capacity for all the mental acquirements and achievements of men, and as generations ensue that capacity will be expanded; the average woman will be as well educated as the average man, and then better educated, for the dormant faculties of her brain will be stimulated to an activity that will be all the more intense and powerful because of centuries of repose. Woman will ignore precedent and startle civilization with their progress.”

—From a 1926 interview by John B. Kennedy, “When Woman Is Boss"


“... The papers, which 30 years ago conferred upon me the honor of American citizenship, are always kept in a safe, while my orders, diplomas, degrees, gold medals and other distinctions are packed away in old trunks.”

—From “My Inventions V – The Magnifying Transmitter," 1919


“There is something within me that might be illusion as it is often case with young delighted people, but if I would be fortunate to achieve some of my ideals, it would be on the behalf of the whole of humanity. If those hopes would become fulfilled, the most exciting thought would be that it is a deed of a Serb.”

—From an address at the Belgrade train station, 1892


Blue Portrait of Nikola Tesla, the only painting Tesla posed for
Public Domain, Wikimedia Commons

"We begin to think cosmically. Our sympathetic feelers reach out into the dim distance. The bacteria of the 'Weltschmerz' are upon us. So far, however, universal harmony has been attained only in a single sphere of international relationship. That is the postal service. Its mechanism is working satisfactorily, but—how remote are we still from that scrupulous respect of the sanctity of the mail bag!"

—From “The Transmission of Electrical Energy Without Wires as a Means for Furthering Peace,” 1905


“What the result of these investigations will be the future will tell; but whatever they may be, and to whatever this principle may lead, I shall be sufficiently recompensed if later it will be admitted that I have contributed a share, however small, to the advancement of science.”

—From “The Tesla Alternate Current Motor,” 1888


“That is the trouble with many inventors; they lack patience. They lack the willingness to work a thing out slowly and clearly and sharply in their mind, so that they can actually 'feel it work.' They want to try their first idea right off; and the result is they use up lots of money and lots of good material, only to find eventually that they are working in the wrong direction. We all make mistakes, and it is better to make them before we begin.”

—From “Tesla, Man and Inventor,” 1895


“Most certainly, some planets are not inhabited, but others are, and among these there must exist life under all conditions and phases of development.”

—From “How to Signal to Mars,” 1910


"When we speak of man, we have a conception of humanity as a whole, and before applying scientific methods to the investigation of his movement, we must accept this as a physical fact. But can anyone doubt to-day that all the millions of individuals and all the innumerable types and characters constitute an entity, a unit? Though free to think and act, we are held together, like the stars in the firmament, with ties inseparable. These ties cannot be seen, but we can feel them. I cut myself in the finger, and it pains me: this finger is a part of me. I see a friend hurt, and it hurts me, too: my friend and I are one. And now I see stricken down an enemy, a lump of matter which, of all the lumps of matter in the universe, I care least for, and it still grieves me. Does this not prove that each of us is only part of a whole?"

—From “The Problem of Increasing Human Energy,” 1900


Nikola Tesla, with Rudjer Boscovich's book "Theoria Philosophiae Naturalis", in front of the spiral coil of his high-voltage Tesla coil transformer at his East Houston St., New York, laboratory.
Public Domain, Wikimedia Commons

“We build but to tear down. Most of our work and resource is squandered. Our onward march is marked by devastation. Everywhere there is an appalling loss of time, effort and life. A cheerless view, but true.”

—From “What Science May Achieve this Year,” 1910


“Everyone should consider his body as a priceless gift from one whom he loves above all, a marvelous work of art, of indescribable beauty, and mystery beyond human conception, and so delicate that a word, a breath, a look, nay, a thought may injure it. Uncleanliness, which breeds disease and death, is not only a self-destructive but highly immoral habit.”

—From “The Problem of Increasing Human Energy," 1900


"It will soon be possible to transmit wireless messages around the world so simply that any individual can carry and operate his own apparatus."

From Popular Mechanics via the New York Times, October 1909


"Let the future tell the truth and evaluate each one according to his work and accomplishments. The present is theirs; the future, for which I really worked, is mine."

—As quoted in Tesla: Man Out of Time, by Margaret Cheney, 2001


“Life is and will ever remain an equation incapable of solution, but it contains certain known factors.”

—From “A Machine to End War,” 1935 [PDF]

Gut Bacteria Could Be Keeping You Up at Night

The bacteria in your gut do far more than help digest food. In recent years, scientists have discovered that they play an important role in myriad bodily processes, from mood and mental health to obesity and gastrointestinal disease. According to recent research, the trillions of microbes in your gut could also impact how you sleep, The Guardian reports.

Though investigation into the links between sleep and intestinal bacteria is just beginning, scientists already know that lack of sleep takes a toll on the body beyond just causing fatigue. It may contribute to the risk of obesity and developing type 2 diabetes. However, digestive processes may themselves affect sleep, scientists now suggest. "There is no question in my mind that gut health is linked to sleep health, although we do not have the studies to prove it yet," psychologist Michael Breus told The Guardian.

A study in Frontiers in Behavioral Neuroscience found that rats fed a prebiotic diet (consisting of fiber that gut bacteria can feed on) had better-quality sleep than rats fed a control diet. The researchers linked this better sleep to increases in the gut bacteria Lactobacillus rhamnosus, a popular probiotic strain. The rats spent more time in REM sleep even when they were subjected to stress, which has been linked to insomnia issues.

To demonstrate how the microbiome affects sleep, though, researchers will likely have to untangle it from the many other ways that the microbiome affects our health, mental and otherwise. Imbalances in gut bacteria might influence depression, which in turn disrupts sleep. Other studies have suggested that poor-quality sleep affects the microbiome, rather than the other way around. Given how much impact the microbiome has on our health, it makes sense that there could be links between major health issues like insomnia and our bacterial colonies. The nature of those links, though, will require much more research to tease out.

[h/t The Guardian]


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