The pipette makes small, light sounds as its thin plastic tip rattles against the walls of the Eppendorf tube. Your hand is shaking wildly. Thumb poised on plunger, you are ready to depress it and release exactly 10µL of Bacillus anthracis liquid culture. This is the Vollum strain, isolated from a cow in Oxford, England. Anthrax strains become more virulent as they pass through more hosts. Vollum 1B is an especially virulent sub-strain of Vollum, and it is what you are currently working on. You do not know this. You are just a lab tech who has been told to pipette this liquid culture into eppi tubes. What you do know is that your boss was arguing with a delegate from the government the other day. Some discussion about the grant your lab received. You’ve heard him argue before, but never quite like this. You think he may have been crying. You heard him yell, “People will fucking die, Chris!” and “I just can’t keep doing this.” The next day someone new was in charge of your lab. You should really keep pipetting this liquid culture.
One of the many things you do not know is that this sub-strain has been passed through dozens of monkeys. B. anthracis is a zoonosis, or a pathogen that can pass between humans and other animals. These are usually especially dangerous to us, because they were not made for our bodies. There are all manner of bacteria that live on and within us. Some biologists even talk of our bodies as a whole ecosystem, as a microbiome. We need bacteria in our guts to break down certain molecules that we could not otherwise digest. We rely on bacteria to build B and K vitamins as well as some amino acids. There are no plants or animals that produce vitamin B12, only bacteria. Large groups of bacteria even help fight off foreign pathogens by competing for nutrients and space.
Microbiota are so important to our healthy functioning as humans that medicine is starting to focus on the microbiome as a way to treat some conditions. Clostridioides difficile is a bacteria which can infect the gut and cause nausea, diarrhea, fever, and abdominal pain. While antibiotics have historically been the go-to method for treating C. difficile, fecal transplants have become a popular alternative and have shown even more effectiveness than conventional methods. Fecal transplants, in which the gut microbiome of one person is placed into the gut of another, are being studied as a possible treatment for all sorts of conditions from Irritable Bowel Syndrome (IBS) to cancer to Parkinson’s disease.
Our microbiota, however, are not only responsible for our response to pathogens and diseases. One noted possible side effect of fecal transplants is weight change. Microbiota are fundamentally important in how we process food. Changes in that system of nutrient breakdown and absorption can have tremendous effects on one’s weight and body composition. Not only that, but gut bacteria have been observed to have an effect on the eating habits of their host. A gut populated with protein-loving bacteria will influence the host to crave more protein rich foods. Conversely, a large population of sugar-loving bacteria can cause one to crave sweets. Gut bacteria have even been found to have impacts on anxiety and depression. The mechanism of action of these effects is not well known.
The mechanism of action for how B. anthracis kills its hosts is, however, very well known. B. anthracis, while in its vegetative state, forms a capsule around itself which contains very few of the polysaccharides that are usually found in such capsules and which the human body’s immune system recognizes as a foreign invader. By not having these polysaccharides, B. anthracis escapes detection. Then, the bacteria starts producing a complex exotoxin, or a toxin which is secreted by bacteria, called “anthrax toxin” which causes a myriad of issues: disrupting cell signalling and communication; making white blood cells undergo apoptosis, or programmed cell death; and interrupting the movement of cells. By primarily targeting the immune system, anthrax makes itself a very difficult condition for the body to naturally fight off.
You are likely well aware of the deadly nature of B. anthracis. It is a naturally occurring pathogen whose effects have been present among humans for thousands of years. It lives in the animals we eat and handle, it lives in the very soil we walk on. The most common form of anthrax infection is cutaneous, or of the skin, with over 90% of anthrax infections being due to contact with broken skin. Broken skin can become infected on contact with a source of anthrax, usually the meat of an infected animal. Once in the skin, it forms a blister which becomes a painless, black necrotic ulcer. Nearby lymph nodes swell, and eventually the bruised and hard lesion forms a scab which falls off, though complete recovery takes longer. Mortality is relatively low, just under 25%. Anthrax can also infect the gut when individuals eat infected meat.
Inhalation anthrax is a more rare and modern disease. Symptoms can take weeks to develop after exposure and are hard to distinguish from the flu or pneumonia. Fever, shortness of breath, and altered mental states are all expected symptoms. Chest lymph nodes begin to swell, the lungs start to fill with fluid. Within hours to days of first signs, the infection can spread from lymph nodes to lungs. Mental alterations become more severe, fevers rise, and shortness of breath becomes extreme. By the time it becomes serious and easily distinguishable from more mild pathologies, death is likely to occur within twenty four hours.
Your hand is shaking as your thumb hovers over the plunger. You press down and release the 10µL of liquid culture into the eppi tube. You place it in its rack and grab the next empty eppi tube. You push the plunger down again to its first stop, place the tip into the liquid culture jar, lift the plunger, bring it to the next eppi tube, and depress the plunger again. You take a deep breath through your respirator, fogging up your goggles as you exhale. It is sweaty in this hazmat suit. The plastic clings to your skin.
In 1942, the British government took 80 sheep to a small island off the North West coast of England. They deployed multiple anthrax bombs and within days, sheep began to die. Gruinard island was contaminated for decades as A. bacillus sub-strain Vollum 14578 proliferated in the soil. In 1986, decontamination efforts began. Tonnes of formaldehyde diluted with seawater were sprayed onto the island, and top soil was removed from detonation sites. Another flock of 80 sheep was released onto the island and were able to survive, so the island was considered successfully decontaminated. It was sold to the heirs of the original owners of the island for £500, attracting much attention from the public, who wanted to get similar good deals on island real estate.
A. bacillus is not out for blood when it infects a host, it’s simply out of place. Like all zoonoses, it is adapted to live happily alongside its host species, much like our microbiota live happily alongside us. Many wild scavengers such as wolves, foxes, ravens, and gulls are known to carry the bacterium with no adverse effects. Its toxic proclivities only become apparent when it is lost and scared, fending for itself in an environment filled with an immune response ready to kill it.A. bacillus is an invasive, an unwitting intruder into a rather delicate machine. It throws itself in between our cogs, mucks up our functioning, just by virtue of it trying to live. It knows not the havoc it wreaks.