Whether a zombie apocalypse is scientifically possible or not, it is better to be safe than sorry. Silly? Perhaps... but even the Center for Disease Control (CDC) wants you to think about zombie apocalypse preparedness.
Being prepared for a zombie attack has never been easier. There are zombie-centric groups like the Zombie Research Society and Zombie Combat Club, numerous zombie survival books and online resources, and even a conference (ZomBcon) that features zombie survival programming.
We know how to avoid and kill zombies, keep from becoming a zombie, stockpile for a zombie attack, pick a location for our zombie-free compound and thanks to The Walking Dead, how to chemically camouflage ourselves among zombies.
The zombies of The Walking Dead pick-out their living animal snacks primarily by smell. They've drawn to noise and use their sight, but these zombies know they've found dinner through smell. As The Walking Dead's Andrea said, "They smell dead, we don’t. That's pretty distinct.” That observation became a plan and The Walking Dead's Grimes got the group of the living chemical camouflage by, ummm... direct harvesting (this episode is called "Guts" for a reason).
After watching this episode, my first thought was, "There has to be a better way." The Walking Dead method (TWDM) for producing said chemical camouflage leaves much to be desired. TWDM requires a corpse, puncturing tools, extensive personal protective equipment (PPE) and a strong stomach. In addition, TWDM is ill-suited for mass production, something a zombie pandemic would necessitate. If smelling dead will save lives, we'll need a lot death cologne.
Fortunately, smelling dead doesn't require dealing with the dead. By selecting the right chemicals, along with suitable production methods, large quantities of a Eau de Death could be made.
For that rotting smell without the fuss and muss of TWDM, two classes of organic compounds - amines and sulfhydryls - offer good bad-smelling chemical candidates. Two foul smelling amines, cadaverine and putresine (Figure 3), are good choices as they are produced early in the body's decomposition process. To the amine duo, the stinky sulfhydryl methanethiol (Figure 3) adds a smell of rotten cabbage or eggs.
For large quanities of our rotten trio, biotechnology could be just be just the ticket, with bacteria doing the heavy lifting. The use of the bacterium Escherichia coli (E. coli) to make large amounts of cadaverine and putrescine was presented in a May 2011 article in the journal Applied Microbiology and Biotechnology. E. coli can produce cadaverine from the amino acid L-lysine by having enzymes trim a carboxylic acid group off L-lysine (Figure 4). The same trim job can yield putrescine from L-ornithine (Figure 4), with L-ornithine being the result of a slice-and-dice of the amino acid L-arginine. There is also a second route to get putrescine from L-arginine without the intermediate L-ornithine.
Our stinky sulfhydryl could also be produced using our bacterial factory workers E. coli (Figure 5), as research published in Plant and Cell Physiology showed. Modifying E. coli to produce a specific enzyme will get us methanethiol from the amino acid L-methionine via a more elaborate route than those that yielded our foul smelling amines.
As with other perfumes, the Eau de Death recipe must be perfected. Should other stinky chemicals be included? What is the proper ratio of stinky compounds to achieve the right rotting flesh smell? Should we have a celebrity spokesperson?
Our chemical camouflage is off to a good start, but we have a lot of work to do. Now is the time to start! We certainly can't wait until we're in the midst of a zombie outbreak. Anyone who has seen The Walking Dead, or any zombie movie for that matter, knows mid-zombie apocalypse isn't the best time for this type of research and development.
______________Figure image attributions: Figures 1-2: clip art from Officer 2010 Figure 5: image from http://bit.ly/qOKEQ2