MIDI-CHLORIANS, HERE ON EARTH! — Star Wars symbionts
Anakin’s home enclosed inside an eukaryotic cell: the nucleus (the perforated sphere), sitting in a half shell of the rough endoplasmic reticulum sprinkled with blue speckles of ribosomes (blue dots) and the tube-like smooth endoplasmic reticulum. Green mitochondria and tiny nutrient spheres float amongst the cytoskeleton lines.
Does the Force run strong in us all? To celebrate the 20th anniversary of Star Wars: Phantom Menace, Bill Sullivan looks at some real-life microscopic powerhouses, including one which could make sense of Jar Jar Binks.
A LONG TIME AGO… well, 20 years ago. That was when George Lucas ended a 16-year dry spell to bring Star Wars back to our galaxy in the form of a prequel trilogy. The primary story revolved around the transformation of Anakin Skywalker into Darth Vader, and gave us the chance to see a young Obi-wan Kenobi and Yoda in their prime. Lucas also introduced memorable new characters like Padmé Amidala, Mace Windu, Darth Maul, and the midi-chlorians. The midi-what?
Most people are trying to forget that Lucas ever injected this concept into Star Wars mythology. In the words of Jedi Master Qui-gon, the midi-chlorians are microscopic symbionts that live inside cells and are somehow conduits of the Force. The midi-chlorians provided a biological basis for Force powers and explained why the Force runs strong in certain people, like Anakin Skywalker.
The majority of fans greeted the idea of midi-chlorians with an iciness that rivals a night of camping on Hoth. Their existence implied that not everyone could train to be a Jedi. The midi-chlorians suggested that becoming a Jedi was more about being born with excessive microbes rather than soul searching on Dagobah. Sensing the disdain fans had for midi-chlorians, future Star Wars films never mentioned them again— as if millions of microbial voices cried out in terror and were suddenly silenced.
As misguided as the idea might have been, there are many Earthly examples of microbes dramatically changing a host’s behaviour. Some can even turn a good person to the Dark Side. In honour of the 20th anniversary of Star Wars: Episode
One, we’re going to discuss some “phantom menaces” that are not so far, far away.
THE CLEAREST PARALLELS to midichlorians right here on Earth reside in all living cells in the Kingdom of organisms we call “Eukaryota”. Eukaryotes include plants, fungi, and animals, as well as single-celled protozoa like amoebas. What eukaryotes do not include are bacteria.
Bacteria are the microbes that gave rise to midi-chlorian-like entities that are essential for every organism in Eukaryota to live: the mitochondria. Mitochondria are cellular organelles that make energy from respiration (oxygen). Plants have an additional symbiont of bacterial origin called the chloroplast, which generates energy from sunlight. These are powers that are just as awe-inspiring as the Force.
Don’t believe me? I find your lack of faith disturbing.
Over three billion years ago, Earth was a cell-eat-cell world. One day in the primordial Rootleaf stew, a large cell engulfed a bacterium. But instead of being slowly digested for over a thousand years, the bacterium somehow evaded destruction and made itself at home inside its predator. The bacterium started replicating into a clone army that evolved into mitochondria.
Mitochondria act like the power converters you’d pick up at Tosche
Station, enhancing its cellular home with an abundance of energy. Some of these mitochondria-containing cells also engulfed a photosynthetic bacterium that became a chloroplast. In other words, chloroplasts and mitochondria used to be two separate types of free-living bacteria that were eaten by larger cells – as Quigon said, “There’s always a bigger fish”. In this case, there was indigestion, and it allowed a partnership to flourish that was mutually beneficial – a process called endosymbiosis that’s likely to be the same one used by midi-chlorians. The resemblance of the term “midi-chlorian” to “mitochondrion” and “chloroplast” is probably not a coincidence.
Let that sink in for a minute. If you thought midi-chlorians were incredulous, keep in mind that every cell in your body has mitochondria, an ancestral bacterium that now gives you power.
MITOCHONDRIAL SYMBIONTS dwelling inside your cells are only the beginning. Your body is home to trillions of bacteria that live inside your intestines, inside your orifices, and all over your skin. Got a bad feeling about this? Collectively, your microbial inhabitants constitute your “microbiota,” and they bring a bounty of new genes into your system called your “microbiome”. The number of bacteria in a person’s microbiota is estimated to be greater than the number of human cells in the body. Consequently, these tiny microbes can have enormous effects on how someone feels and behaves. Judge them by their size, we should not.
Many of the startling findings about the intestinal microbiota come from studies performed on germ-free mice, which have no microbes in or on their bodies.
This allows scientists to implant various microbes into their guts (we don’t need to go into the unsavoury ways this is done) and observe their effects on personality and behaviour. The results of these experiments suggest that gut microbes influence a wide range of traits, from appetite to mood.
In a study by the Center for Genome Sciences and Systems Biology, Washington University School of Medicine, germ-free mice implanted with intestinal bacteria taken from obese people began to overeat and became obese; if given bacteria from lean people, the mice remained lean.
In another example from Ireland, reported in the Journal of Psychiatric
Perhaps Obi-wan should have slipped some probiotics into Anakin’s Bantha milk to keep him from turning to the Dark Side
Research, germ-free rats given intestinal bacteria from people who are clinically depressed soon developed symptoms of depression, too – becoming anxious and uninterested in sweets. Germ-free rats given bacteria from people who are not depressed did not develop symptoms of depression. If gut microbes can indeed affect mood, perhaps Obi-wan should have slipped some probiotics into Anakin’s Bantha milk to keep him from turning to the Dark Side.
The intestinal microbiota appear to have a commlink to our brain, possibly through the vagus nerve, which connects the brainstem to various parts of the body, including the digestive system.
Some of the ways these intestinal microbes can exert their surprising effects on our mind could be through the myriad of chemicals they produce. Some of these microbes manufacture important neurotransmitters like serotonin, some influence the immune system, and some make butyrate, which can affect levels of gene activity in our cells. One recent study published in Cell Metabolism isolated a rare type of alcohol-producing bacteria from the guts of people with auto-brewery syndrome, a bizarre condition that gets them drunk even though they’ve consumed little to no alcohol. Perhaps this could explain the silly high jinks of Jar Jar Binks?
The microbiota makes it conceivable how bacterial symbionts can bestow superpowers of sorts, albeit not the kind that can levitate rocks or Force push an enemy. Clear demonstrations of symbiont superpowers have mostly been demonstrated in other species.
The coffee berry borer, for example, draws its sustenance solely from coffee berries – consuming the equivalent of
230 cups of coffee per day. This little beetle can tolerate such extreme levels of caffeine thanks to a bacterial species in its gut called Pseudomonas fulva, which carries a gene that makes an enzyme that cuts through caffeine like a lightsabre through a battle droid.
Another superpower bacteria can grant is thermal tolerance. The “plant lice” insects known as aphids can withstand hotter temperatures better when carrying a symbiotic bacteria called Buchnera aphidicola. Some of us humans may also
harbour bacteria that grant superpowers. A study published in Nature Medicine reported that when bacteria from elite athletes were given to mice, the mice were able to run on a treadmill for longer.
WHILE MIDI-CHLORIANS are characterised as symbionts, viral infections or parasites can also manipulate behaviour in their host. Sometimes this has catastrophic consequences, such as in the case of rabies, a virus that can transform a gentle porg into a beastly wampa. By turning its host into an aggressive monster, the rabies virus increases its chances of spreading to a new victim through the bite wound.
A stealthier pathogen that can alter host behavior is Toxoplasma gondii – a singlecelled parasite that causes rodents to lose their instinctual fear of cats. Cats are the only host in which the parasite can complete the sexual stage of its life cycle, so it makes
sense that Toxoplasma would hijack the rodent brain to turn it into an easy meal for cats. The creepiest part is that Toxoplasma
can infect the brain of any animal, including humans. Unless the person is immune compromised, Toxoplasma produces no overt symptoms of illness, but strange correlations have been made suggesting that the presence of the parasite transforms how that person behaves.
A Brazilian study from 2018 showed that people infected with Toxoplasma
have a higher frequency of risk-taking, rage disorder, and anxiety. Consistent with increased risk-taking, people with Toxoplasma are more likely to exhibit entrepreneurial behaviour, be in a traffic accident, or attempt to navigate an asteroid field despite the odds being 3720 to 1.
The idea of midi-chlorians was not welcomed into the Star Wars universe, but like it or not, microbial symbionts have a profound influence on just about every lifeform on Earth, including you. Their Force will be with you…always.
A rare type of alcoholproducing bacteria gets people drunk even though they’ve consumed little to no alcohol. Could this explain Jar Jar?
BILL SULLIVAN is the author of Pleased to Meet Me: Genes, Germs, and the Curious
Forces That Make Us Who We Are (National Geographic Books). He is a professor at the Indiana University School of Medicine in Indianapolis, where he studies infectious disease. Visit him at authorbillsullivan.com or follow on Twitter @wjsullivan.