• Microbigals

The Grim Reapers Microbial Form: Yersinia pestis AKA the Black Plague

Updated: Sep 17



Welcome everyone to today's class, we are talking about one of my idols, and possibly the grim reaper in physical form, Yersinia pestis bacterium. We will discuss how the black plague spread, who caused the black plague. Now, Yersinia pestis, has one of the highest body counts out there which is one of the many reasons I idolize this beautiful bacteria.


Cartoon drawing of yersinia pestis bacterium and the lecture of today's talk Becky Lafarge. The words say "Yersinia pestis the grim reaper of microbes lecture by becky lafarge only @microbigals

Student: Uhh Ms. Lafarge, isn't that a little Dark?
Far from the darkest thing I have ever said, I can go darker if you would like.
Student: No… please don't.
Ok fine party pooper; let’s get on with our lecture.

I’m sure everyone here has heard of the Black Plague or the Black Death. This disease came in several devastating waves, wreaking havoc on the medieval world of the giants; it was a distant yet intriguing time in history. A time wear the Grim Reaper took form as Yersinia pestis bacterium and spread through most of the world.


But, did you know Yersinia pestis is still lurking around


day? It's True! It infects less than 5,000 people annually worldwide, however, they have harnessed the use of antibiotics these days which serves as a viable treatment for Yersinia pestis today.


Throughout history, many giants have tried to conquer great spans of land, but few have had more success in conquest than Yersinia pestis.


Student: This microbe doesn’t sound like it gives us a good wrap to the giants.

Well maybe they need to be scared a little, many great things have come from fear you know. So while yes it may not give us a good wrap in the eyes of the giants it is one of the few us they can name. And what do They always say about publicity….anyways moving on.


To discuss how the black plague spread, let's go back to the year 1347, an excited group of townspeople raced through the fog to the docks, eager to greet the incoming ships that, for weeks, have been the homes of their loved ones. A sigh of relief swept across the townspeople knowing the ship meant there was a chance their husbands, their sons,

Picture depicting one way how the black plague spread. It's a ship with Yersinia pestis bacterium hidden in the sails

might not have perished in the war at the very least they were not lost at sea. The sight of that ship was an end to their waiting, to them not knowing if their family member was dead or alive. But just as quickly as the town let out that sigh of relief, the gasps of horror echoed through the harbor town. 12 ships docked at the Sicilian port. Women gasped, children cried, some ran away in horror, It was worse than they could’ve ever


expected. The grim reaper had come to town. Beautiful isn't it?


Student: Actually terrifying.
You keep that attitude and I'll show you something terrifying.
Simon: Becky! Out of line.
Oh boo, you’re no fun. Where was I? Oh right.

Stacked in large piles, the smell of decay quickly permeated through the city. Those that were still alive walked like zombies. Weak and sickly sailors staggered out of the ships covered in grotesque black boils, oozing blood and pus. The townsfolk were horrified and didn't know what to do. In an effort to protect themselves, the dead and dying were ordered to sail out to sea and never return again. But it was already too late, Yersinia pestis had arrived, and there’s little hope of escaping the Grim Reaper of Bacteria.


Simon: Ok enough with the grim reaper business.
Humph! Where's your spooky spirit!

Yersinia pestis Bacterium


The giants often describe the black death as the greatest catastrophe there ever was, wiping out 20-50 million people in the 14th century, forever altering their future as a species. Waves of pandemics can be seen throughout history, but it was the second black death pandemic that caused the greatest shock waves. The black death of course was caused by the one the only Yersinia pestis bacterium. So let’s get to know one of the Society of Symbionts Most Wanted.



Yersinia pestis finds its typical home on rodents, not just rats, but squirrels, prairie dogs, chipmunks, voles, and rabbits can all also be affected by it. Actually, Yersinia pestis lives in the fleas, hitchhiking on these rodents. This bacteria favors the fore-gut of the flea where the microbe creates a sticky biofilm. A biofilm is like a microbial apartment, a safe space for the bacteria to flourish.

Picture of Becky Lafarge in front of a power point presentation showing the animals for which Yersinia pestis can call home, which includes rats, squirrels, prairie dogs, chipmunks, voles, and rabbits


The biofilm does two things here, the first is the typical biofilm purpose; protecting the fellow microbes. The second one is a little diabolical, more up my alley. In fact, it is one of the most manipulative and terrible things I have ever heard of, way worse than hijacking someone else’s cell for self-promotion.


Student: Man, I’m glad you are reformed.
For now....
Simon: what?
I didn’t say anything.

The extensive biofilm is actually so thick that the flea’s food cannot reach its gut, meaning no matter how much the flea eats, it is starving. This causes it to go into a feeding frenzy, violently biting and eating whatever it can, all the while the flea's food cannot go down resulting in the flea regurgitating its previous meal back into its new host. This sounds like a personal hell for the flea but is great news for the bacteria which can now spread farther and reproduce more. Microbes can be diabolically clever in the most terrifying ways.


It’s thought that the fleas jumped from rats to humans, biting them resulting in infection. Human to human transmission can also easily occur when someone comes in contact with infectious droplets, tissues, or fluids, and then you have a pandemic.


The genus of Yersinia only includes a few pathogens, Y. pestis, Y. pseudotuberculosis, and Y. enterocolitica. The latter two are food- and water-borne diseases that are not nearly as virulent as Y. pestis.


Genetically, Y. pestis and Y. pseudotuberculosis are very similar, so similar they could be considered subspecies rather than different species. Despite their similarity, these two are very different in their transmission and virulence.


The plague does not come in 1 form, but in 3 distinct types: pneumonic, septicemic, and bubonic. The most common form is bubonic where the defining characteristic is buboes which are lymph nodes that swell to around the size of a chicken egg and typically occur in the neck, armpit, and groin within the first week of infection. These buboes can ooze, the person does not smell good and can have pains, chills, diarrhea, and fever. If untreated the infection can spread to the lungs (called pneumonic) or the blood (called septic).


Pneumonic is the least common, but it can transmit from person to person causing a form of pneumonia with symptoms that can start hours after infection leading to difficulty breathing, bloody phlegm, high fever, chest pain, headache, nausea and vomiting, and eventually respiratory failure, shock, and death if not treated with antibiotics within a day after infection. It is also the most deadly, with almost 100% mortality.


The last form is septic, where the bacteria enter the blood and spread throughout the body. This leads to fever, weakness, abdominal pain, nausea and vomiting, bleeding from the mouth or nose, and tissue death in the extremities causing them to turn black.


Another Theory To How The Black Plague Spread


Due to records and how long ago it was, it is hard to pin down exactly how the black plague spread to the size that it did. It is suggested that this pandemic started in 1346 in Mongolia where humans may have gotten it from interacting with marmots. From here, It is spread by Mongols and laying siege to Genoese.


This brings us to perhaps the first account of the giants using microbes as biowarfare. They had no clue what we were and definitely didn’t know who Yersinia pestis bacterium is. All they knew was that soldiers were dying of this disease and those that came in close contact with them all seemed to die. So, perhaps in an even more diabolical plan than Yersinia pestis thought up, came from the giants themselves. They catapulted the decaying dead soldiers into the city. Survivors eventually crawled their way back to Europe in hopes they would find safety. But all they did was spread Yersinia pestis throughout their homelands. Eventually, a second and third strain entered Europe and spread throughout. Without the scientific knowledge of today, they were doomed. They had no clue what was causing it, never mind how to cure it or stop it. All they could do was try to survive as everyone around them died. Eventually the event we know as the Black Death petered out in 1351, wiping out roughly 25-50%of the inhabitants of Europe.


You may be asking yourself, what about the first wave? Why don’t we talk about that? Well, that occurred in 541-544 and originated in Africa and spread throughout the world. It was called the Justinian pandemic after the Roman emperor at the time, and the focus of the pandemic was Istanbul with 5000-10000 dying daily. In the end, almost 100 million were dead. Yersinia pestis did not completely go away as Europe saw outbreaks over the next centuries.


There were outbreaks again after this pandemic such as the London outbreak occurring from 1665-1666, but a third pandemic broke out in 1894. It started decades earlier in China, eventually hitting all the continents by 1900 and eventually stopped in 1959 causing 15 million deaths, a lot less fatal than the previous plague but still deadly. Today Yersinia pestis can still be found on almost all the continents and is still found in the western US, but most cases since the 1990’s have happened in Africa.


Wanted poster showing Yersinia pestis bacterium

Student: Wow so many dead.
Not compared to how many of us have perished from things like antibiotics, but we will rise again.
Student: You mean help them out right?
Riiiiiiigggghhht.
Simon: Why did you wink?
Oh nothing, just something in my eye.

It was not until hundreds of years later, during the third great plague pandemic, that the causal agent was identified by a French microbiologist Alexandre Yersin for whom the bacteria is named. The same year (1894) that Yersin isolated the bacteria, a Japanese bacteriologist, Shibasaburo Kitasato, also independently discovered it on an unrelated research project. Both Yersin and Kitasato were nominated for the Nobel Prize, but Yersin was the one to be awarded the distinction.


Fleas may have been the start of the plague but how the black plague spread to the point it did has to do with their own immune system. When it became pneumonic, people started to cough or sneeze, releasing droplets with Yersinia pestis bacterium inside leading the pneumonic form to spread as well. Do you know how they keep saying to wash your hands? Well, that's truly one of the greatest ways the giants protect themselves from the Society of Symbionts Most Wanted List. Sanitary conditions were not good during the first 2 pandemics, allowing the spread and festering of rodents who contributed; bodies were piling up which meant more food for them which meant more rats and more fleas. This was truly an awesome superstorm of death.


Treatment For Yersinia Pestis


Now let’s talk about some of the “treatments” that were used during the second pandemic for Yersinia pestis bacterium.
Student: Teacher, did you try to make air quotes? You don't have any arms.
Keep insulting me and you won't either.
Simon: Becky!

Ok sorry, sorry, how about detention instead?
Simon: Better. Although still a little extreme....?

So during this plague, ‘doctors’ would “treat” patients with the ghastly techniques of bloodletting and boil-lancing,


and after lancing the buboes, they would apply a paste that had their own excrement as a main ingredient. Excrement! Treatment for Yersinia pestis? More like adding insult to injury. Can’t imagine anything more insulting than smearing a bit of your own poo on you while blood gushes out of your hopeless life drained body. Other useless, but less harmful treatments for Yersinia pestis include burning aromatic herbs and bathing in rosewater. The upper echelon even tried unicorn horns, which did not really exist and


were more likely narwhal horns, and grinding up emeralds to consume, truly a weird species. The fact they believed in unicorns before they believed in us is still astounding. Although they may seem primitive, proper sanitary conditions, hand washing, and masks are the number 1 defense against all sicknesses. Many lives would have been saved in 14th century Europe if they only knew what the giants now know today!


So how did the plague end? By means of social distancing. People suspected of being sick or at high risk, such as sailors were quarantined until they were deemed safe to enter the city. The royalty and upper echelon were the ones who fared best because they were able to retreat to the countryside where they could distance themselves from everyone else.


The End of Yersinia pestis bacterium as the Giants Grim Reaper

Human Microbes, History and Science, Microbe News

So much happened as a result of the plague. The entire social dynamic



of Europe changed due to so many deaths. The church lost influence as people saw that they could not help or protect anything any better than anyone else during this plague of Yersinia pestis. Jewish identifying people were also blamed for the plague; it was thought they were poisoning the water due to some agenda. As a result, an untold number were massacred causing many to flee to what is now Poland. Today, though, the giants have a real treatment for Yersinia pestis, antibiotics.


Well, that is it class, next time we will talk about Dreadful mummies and the bacterium Clostridium botulinum. But in the meantime, review today's class as there may be a pop quiz.


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