There are lots of reasons we don’t see huge, multicellular bacterial creatures running around on land, but the biggest reason is that bacteria are barely more than bags of soup. The bacterial genome floats in the main cell compartment right along with its protein products, waste from the cellular processes, and every other reaction in the cell.That’s fine if all you want to do is eat and divide, perhaps flap a tail for sperm-like locomotion, but far too difficult to control if your goal is even slightly more complex. Specialized cell types that work together to make something as complicated as, say, a dust mite, require a much finer ability to control internal processes than one huge reaction pool could possibly provide. Evolution solved this problem by creating a new class of life that cordoned off different sorts of actions in different sections of the cell — we call these eukaryotes, and we still don’t understand them very well at all.Probably the biggest impediment to truly understanding eukaryotic cells, which encompass plants, animals, and fungi, is that their many compartments communicate and pass products around as needed. A protein might be first made in the endoplasmic reticulum, move through some portion of the Golgi apparatus, then somehow end up embedded in the exterior membrane. Such localization is the reason eukaryotes came about in the first place, of course, but biochemists have long been vexed at the prospect of following a particular protein through all the intermediate steps it takes in its lifetime — and more importantly, at the prospect of controlling those steps.The latest Nobel Prize in Medicine was handed out this week for several decades of work done on solving just this problem. The recipients collectively provided a wealth of evidence for a new model of protein traffic inside a cell, one that begins to offer scientists a way to predict and even influence that traffic. Their model proposes a lock-and-key mechanism in which the first organelle (a cellular compartment or “organ”) buds off a bubble full of our protein(s), one studded with the molecular key. This protein transport bubble, called a vesicle, floats through the cell until it bumps into the intended recipient organelle, where the receptor molecules grab hold of the vesicle and fuse with it, consuming its contents.What does this mean for you? Protein traffic is such a basic process in plant and animal cells that it could be said to underlie virtually everything they do, but some diseases are linked to faulty protein traffic more directly. Certain types of diabetes, for instance, arise from an inability to read and respond to signals about blood sugar levels. The winners’ past work has been used to improve diagnosis and treatment of several types of immune disorders and childhood epilepsy.With a detailed enough understanding of protein traffic, however, we could potentially cure all kinds of different diseases. There’s increasing evidence that a trafficking problem is the cause of many cases of Alzheimer’s disease — and understanding precisely where that problem occurs is the first step to fixing it. If, say, a protein is missing a particularly important modification on its way to a job site, we now know enough to significantly narrow the search for culprits. Find it — perhaps it’s a mutated signalling molecule that doesn’t allow fusion with the proper target — and correcting the problem becomes a matter of engineering.In fact, pretty much every advance in neurology relies at least somewhat on this work. Neurons in the brain release and take up neurotransmitters with very similar processes, sending vesicles back and forth — though this time the bubbles ferry proteins between two cells rather than within one. You can thank our understanding of vesicle traffic for the explosion of psycho-active drugs in the past twenty years or so. Again, understanding the complex processes that underpin life is the hard part; once understanding is in place, manipulating those processes is what we’re best at.That’s why this research received the Nobel Prize: after all these years, the field these three researchers largely pioneered has continued to bear fruit across more and more areas of research, to allow progress in fields all over biology, from epilepsy to schizophrenia to Viagra. It’s a process that allowed life to give rise to the amazing diversity we see today. We’re just now beginning to grasp how it works.