Zombie biology, Pt. 1: Richard Matheson’s bacterial symbiosis

This is the first post in a 5-part series on the biology of zombies. More info and links to other posts here.

A little girl zombie eats her victim in Night of the Living Dead

The rise of the zombie in pop culture is typically credited to George Romero’s ghouls from his Night of the Living Dead films, whose dead bodies reanimated with a taste for human flesh define our prototypical zombie. Romero doesn’t give a clear cause for their rise from the grave, with a vague mention in a television broadcast of a satellite returned to Earth from Venus emitting radiation. (Radiation could do anything back then!)

In a behind-the-scenes special about the making of the movie, Romero credits its creation to a short story he had written, “which I basically had ripped off from a Richard Matheson novel called I Am Legend” —  a great horror story about Robert Neville, a man fighting for his life in Los Angeles against vampires. But the novel takes the vampire prototype and turns it on its head, with these creatures more recognizable as zombies to us than vampires. They aren’t the sneaky serial-killer types, but are rather stupid and gather in great hordes, and, like zombies, will feed upon one another if they must. (Yes, they have blood!) In an early chapter, Neville reads Bram Stoker’s novel Dracula (as he sips whiskey and listens to Brahms while vampires scream outside his house), describing it as “a hodgepodge of superstitions and soap-opera clichés” compared to his situation at the time.

Most of the standard vampire tropes hold true: they’re sharp-toothed, blood-sucking, repelled by crosses and garlic, and can’t come out in the sunlight. But this is science fiction — there must be a scientific cause for these symptoms! While he’s skeptical of the scientists’ germ theory of vampirism that was proposed before the scientists became vampires themselves, Neville eventually overcomes his “reactionary stubbornness” and gets a microscope. (And Matheson doesn’t leave out the difficulties of microscopy or mounting samples, with Neville throwing his first scope across the room in frustration.)

When he finally gets his slide loaded with a sample of vampiric blood, he is shocked to see a bacterium in the sample — a bacillus, “a tiny rod of protoplasm that moved itself through the blood by means of tiny threads that projected from the cell envelope.” And from there much of the book turns to scientific inquiry with many moments that made me smile, like when Neville so urgently “needs to know!” that he nearly runs out of the house into a vampire horde. Oh, the drive of science! Or when he can’t make the pieces fit into his bacterial model and begins to work himself up into a fury:

He made himself sit down. Trembling and rigid, he sat there and blanked his mind until calm took over. Good Lord, he thought finally, what’s the matter with me? I get an idea, and when it doesn’t explain everything in the first minute, I panic. I must be going crazy.

But over the course of years, performing experiments on captured vampires and their blood samples, as well as doing a lot of hard thinking, Neville manages to explain to himself why the vampires act the way they do. Whether his explanations will be good enough for you is another question.

The bacterial lifecycle

Bacteria from the same genus as Neville -- this is Bacillus subtilis, while he found Bacillus vampiris

“I dub thee vampiris,” he says to himself when he sees the bacteria for the first time. The bacteria live in the bloodstream of their host and require fresh blood to live, living in a kind of symbiosis (described thus by Neville), with the bacteria generating energy for their hosts. But if there isn’t enough fresh blood around, a bacterium will sporulate, building a cell wall around itself to hide out until better conditions arise. When the host dies, these spores disperse, landing on a new host, with the new source of fresh blood reviving the vampiris bacterium.

In the novel, the bacteria were able to spread rapidly through the population due to dust storms, with the wind blowing the spores everywhere and the dust nicking peoples’ skin and thus creating a way into the body.

Neville’s discussion of bacteriophages is a moment of total scientific inaccuracy which I choose to ignore. His bacteriophages, which he describes as proteins that the bacteria secrete when conditions are poor, cause the bacteria to swell and explode, killing themselves along with the hosts’ cells. The thinking must have been that the bacteria need a way to kill their hosts so that their brethren spores can disperse — however a bacteriophage is not a protein, but rather a virus that infects bacteria.

Death by stake — an issue of bacterial metabolism

These vampiris bacteria can live with or without oxygen — aerobic or anaerobic metabolisms. In the bloodstream, they live without oxygen, but the second oxygen hits the system, they become parasitic, killing their host. And here’s where the stake comes in: The key to killing these vampires is creating a hole large enough to let oxygen into the bloodstream, causing the host to die immediately due a switch in bacterial metabolism. And when the host dies, the spores are released — and thus we have vampires exploding into dust. Once Neville realizes that it’s an issue of oxygen and not stakes or their material, he switches his method to simply slitting the wrists of the vampires to let oxygen in. “When I think of all the time I used to spend making stakes!” he says.

And why don’t bullets kill vampires? This is some embarrassing fabricated “science:” The bacteria cause the creation of a “powerful body glue” that seals bullet holes as soon as they are formed. (Though this body glue somehow can’t reseal the wrist slits.) The stake creates a large hole and blocks the body glue from resealing it, which is why they are such a potent weapon against vampires.

Other bacteria-based vampire symptoms

Philip Burne-Jones's painting The Vampire (turn of the 20th century)

Neville read that strong sunlight kills bacteria, which is why vampires can’t go out in sunlight. But without fresh blood, the bacteria can’t create energy — resulting in the coma-like state of the vampires during the day.

One of his first experiments is trying to work out the vampires’ aversion to garlic. After reading that garlic’s potent odor is caused by allyl sulfide, he goes to a chemistry lab and heats mustard oil and potassium sulphide at 100 degrees to create the compound. First he tried injecting it into a vampire — but nothing happened. He expected the bacteria to be killed by the allyl sulfide in a lab experiment, yet again nothing happened! He was so infuriated by this failure of his theory that he downed a bottle of whiskey, broke a bunch of glass, and shredded a mural he painted.

World’s gone to hell. No germs, no science. World’s fallen to the supernatural, it’s a supernatural world. Harper’s Bizarre and Saturday Evening Ghost and Ghoul Housekeeping. ‘Young Dr. Jekyll’ and ‘Dracula’s Other Wife’ and ‘Death Can Be Beautiful’. ‘Don’t be half- staked’ and Smith Brothers’ Coffin Drops.

He stayed drunk for two days and planned on staying drunk till the end of time or the world’s whisky supply, whichever came first.

Yup. Just a normal day in the lab.

He later realized that this chemical in the bloodstream wasn’t enough. It was the actual odor of the garlic that did harm — an allergen that sensitized and repelled the bacteria, and hence their hosts. Tells you something about in vitro and in vivo experiments, am I right?

“The germ also causes, I might add, the growth of the canine teeth,” he mentions once near the end of the novel. Good save, Matheson.

Vampire psychology

Neville wasn’t satisfied by this theory alone — what about the mirrors and crosses?

A new approach now. Before, he had stubbornly persisted in attributing all vampire phenomena to the germ. If certain of these phenomena did not fit in with the bacilli, he felt inclined to judge their cause as superstition. True, he’d vaguely considered psychological explanations, but he’d never really given much credence to such a possibility. Now, released at last from unyielding preconceptions, he did.

Before society collapsed entirely when vampirism was spreading, in terror people turned to religion to calm their fears — The vampires were cursed by god for their sins, and only by accepting god could you be saved! Neville theorized that when these people, now convinced that evil people were condemned to vampirism, were infected by the bacteria and found that they themselves were vampires, they were driven mad. The mere sight of the cross — a symbol of their rejection — made them want to flee due to their self-hatred.

But the cross doesn’t apply to everyone, he noted. He had one Jewish friend that, as a vampire, was not repelled by the cross. But the sight of the Torah made him run in fright!

Mirrors had a similar effect. Having to actually face the fact that they were vampires visually was enough to drive them nuts and induce them to flee.

Ending teaser (but not a spoiler!)

There are a few other awesome biological references in the novel — including the lymphatic system, medical applications and evolution, which I won’t go into detail about here so you can enjoy the read. But I will tease with this quote, especially appreciating that this book was written in 1954.

He looked into the eyepiece for a long time. Yes, he knew. And the admission of what he saw changed his entire world. How stupid and ineffective he felt for never having foreseen it! Especially after reading the phrase a hundred, a thousand times. But then he ’d never really appreciated it. Such a short phrase it was, but meaning so much.

Bacteria can mutate.

Bacterial vampirism: it’s awesome!

I’m no expert, but this was the only example of vampirism being caused by bacteria that I could find. This novel certainly inspired many later stories of plague-based apocalypse and biological transmission of zombie-ism, but, after a few decades of focusing on radioactivity and biological warfare, the genre switched straight to viruses (to be discussed later this week) and never went the bacterial track.

But there’s plenty of good reason to consider bacteria and other spore-based organisms when developing your zombie mythology, especially since there are a number of examples in nature (also to be discussed later). It’s an underexploited transmission mechanism! Get on it, filmmakers.

And one final note — I Am Legend is really awesome and you should read it. Trust me — there is MUCH to enjoy despite what you’ve read here. This is really a novel about human loneliness, perseverance, and our definition of normalcy, after all.