Previously, we looked at the zombie fungus that plagued carpenter ants and turned them against their colonies in the rainforest. Now, we will look at bacteria and the object of their zombification and destruction: silver. Throughout our history of fairy tales and legends, silver has been the downfall of many mythical creatures from werewolves to monsters that hide in the shadows. For thousands of years, silver has been used in medicine and as an antibacterial agent [1]. Nowadays, hospitals use silver to help patients recover and prevent infection. They use silver-based bandages, catheters, and other items in order to prevent bacterial growth [1]. Even consumers can get silver-based doorknobs, washing machines, and other silver products for their homes to prevent and slow down the growth and spread of bacteria all while also keeping werewolves out of your home [1].

Silver ions work their magic by tearing into bacterial membranes and breaking down everything inside like DNA, which is crucial to their existence and ability to function [1]. While the bacterial fighting powers of silver have been known and used for some time, we did not know about their “zombie” effect on bacteria until a team of scientists in 2015 uncovered their secret. The effect is fairly straightforward. The scientists started by infecting a sample of bacteria with silver, in the form of silver nitrate, until all the bacteria were dead [2]. They then isolated a dead bacteria (the infected “zombie”) and introduced it into a colony of living and healthy bacteria [2]. Just as what you would expect from a zombie plague on unsuspecting humans, the healthy colony was destroyed (99.9%) with the introduction of the zombie bacteria [1].

The question now becomes: how does a dead bacteria, killed by silver, go on to kill living bacteria without the introduction of more silver? The answer is fairly similar to the zombie fungus and its use of the of the carpenter ant. After the ant is killed by the zombie fungus, the stroma accumulates spores that are then released into the surrounding area to be picked up by further ants, spreading the fungus and the eventuality of death. With the zombie bacteria, once the corpse starts breaking down it releases silver particles that have accumulated in its body [2]. These particles spread across the colony and infect subsequent bacteria until they die. Then, these newly killed bacteria spread the particles further from their dead corpse and so on until the colony is decimated. The bacteria act as sponges because they easily absorb the silver particles, which hastens their death [1].

This novel finding of the ability of dead bacteria to spread these silver particles does create many opportunities for us to use against bacterial infections for prevention and treatment. This is especially significant given the rise of antibiotic resistant bacteria around the world and, most critically, in hospitals. More in-depth research into the zombie effect would allow us to build better antibacterial systems that use either the silver particles or the dead bacteria [1]. Extending both over the long term would create a bacteria-limited area and reduce infection risks for many patients. Among zombies, this one is probably one of the few who could actually benefit humans instead of destroying us.

More research is needed to explore the positive effects of this and as we continue to explore this and other methods of combatting antibiotic resistance, maybe we will uncover other zombie effects that can provide us with positive benefits. Antibiotic resistant bacteria may not be the only terrors waiting for us as there may be terrible diseases and disasters waiting to wake up from the cold slumber beneath frozen lands. The more tools we have to fight them the better.

Photo acquired from Wikipedia of Pseudomonas aeruginosa (the bacteria used in this experiment)