According to the tale of Caesar’s last breath, each breath we draw probably contains a few of the molecules that escaped with his last. That assumes of course, that those 1022 molecules were more-or-less uniformly mixed with the 1044 molecules in the atmosphere. When acting blind, as with the simple inert molecules in the air, this great thermal mill only homogenizes. But if purposed with more versatile actors, it becomes the universal constructor that knits order into every cell in our bodies, molecule by molecule. When instead of gases, the molecules are snippets of DNA — barcodes if you will — they can be used to discreetly, and unambiguously, mark almost anything. With the right molecular touch, it is possible to determine where something first came from, and where it has been.

Researchers at the University of Aveiro in Portugal are developing DNA barcode tags that can be harmlessly applied to a wide variety of products, even foods or liquids. Each tag is a unique combination of DNA base pairs that attach to most surfaces, and can later be collected, amplified, and sequenced. The power of this technique lies in the uncountable micro-matings that take place in the DNA solution where the primary goal is to determine like from unlike. Every known sequencing method has some margin of error, and the chance of false positives or false negatives exists whenever the signal to noise ratio is too low.

For example, in some schemes a DNA “fog” might be used to spray violent protesters when there are not enough law enforcement personnel to immediately subdue the lot of them. That tag will be unique, and mark anyone who bears it, at least for a while. Over time however, the signal will spread and degrade. Multiple tags could be used to mark multiple events or increase reliability of a single event. Clearly though, finding a way to contain your marking agent at the outset is the cleanest option.

The general concept has been around for some time, particularly as used by biologists to track and identify species. One major project, known simply as the barcode of life, now has over 200,000 animals cataloged in a searchable database. Since things like animals already come pre-barcoded, all one need do is find some region in their DNA that tends to mutate fast enough over time so that each species can be expected to show enough variation. Usually a 600-spot region in a mitochondrial gene known as cytochrome oxidase I is used. These oxidases are essential enzymes which perform functions like degrading caffeine, and many other drugs, into products that can be removed by the body.

The most imaginative use for DNA barcodes is to trace neurons, and their activities, within the brain. The original BRAIN Initiative, before its initial aspirations were chopped back, called for something even more dramatic — growing barcodes that stored vast amounts of information in real time. In other words, molecular ticker tapes built into every neuron. DNA sequencing pioneer George Church holds the patent for a so-called nucleic acid memory device. This concept uses a specially constructed DNA polymerase (an enzyme which copies DNA) to directly transmute voltages appearing across the membranes of cells into DNA base pair patterns. By using several ticker tapes to create a sufficient level of redundancy, an arbitrary degree of accuracy can be achieved, all within the existing energy budget of the cell.

Some of these concepts will be undoubtedly be harder to implement than others. A simple DNA paint might be something we could buy at the store or make at home with little effort. DNA may be everywhere right now, but compared to what soon may come, we could literally end up swimming in the stuff.

Now read: Molecular threading: A powerful tool for DNA sequencing

Research paper: doi:10.1371/journal.pone.0035858 – “A Ranking System for Reference Libraries of DNA Barcodes: Application to Marine Fish Species from Portugal”