Whether we like bugs, viruses or creepy crawlies of various stripes does not really matter. But we do have to admit that each of them has, as a species, survived for a long time. Each one of these critters has consistently been more competitive than all challengers. It has been superior to others and therefore is in some sense optimal. Each has passed the strict test of evolution by surviving in an often hostile world. We might actually be forced to admit that each one of them is perfect in its own way.

So, if a bug is perfect, can it be improved? Why should we even think about changing it? Practitioners of the new fields of synthetic biology and metabolic engineering, which could be considered prominent applications of systems biology, certainly believe that exactly that could be very rewarding. Synthetic biologists and metabolic engineers have no problem with the argument that bugs are perfect, but their rationale for trying to change them derives from the fact that perfection may be judged by rather different criteria.

A mathematician might say that the bug has to solve a “multi-objective optimization” task. It must optimize many objectives simultaneously, and these objectives are often in conflict with each other. We deal with such tasks every day. For instance, buying a winter coat involves numerous objectives that should be satisfied and, ideally, optimized. The coat must have the right insulation for the expected temperatures, we really want to like the material and color and, of course, the price must be right. Abundant experience tells us that we are seldom able to satisfy all criteria completely and that we must prioritize or compromise by weighing different aspects against each other. Even the nicest coat is out of reach if we cannot afford it.

All organisms in the real world have this type of problem throughout their lives. Above all, they must ensure that their species survives and proliferates. This overarching objective involves uncounted smaller tasks, as the organisms need to be tolerant to environmental perturbations, fight off, avoid or flee from hostile challengers, appeal to potential mates, and bring their young ones to independence. The rationale of metabolic engineering for altering organisms is that if one relieves the organisms of some of these tasks they should be able to devote energy to others.