Cloudscape

Synthetic organisms were of immense potential in medicine. They were capable of doing things ordinary medicines could not (especially virions), because they could get macromolecules such as proteins into the body, whereas all other medicines were smaller molecules: orally administered macromolecules would be broken down in the digestive tract.
This was so significant because in this way one could directly affect every single substance in the entire body, notably proteins - enzymes, cytokines, and so on. It was wonderful that, just like we could administer medicines, we could now likewise administer enzymes. This broadened our horizon of approaches immensely because through this technique we could influence all the machinery in the body, and therefore all of the body itself.
Whether proteins can still be called "substances" or were, strictly speaking, actually "structures," or a combination of both, was debatable. After all, being nanomedicine, this methodology straddled the line between medicine, the molecular, and nanotechnology, the supramolecular.
The advantage of this approach was that it could be made more balanced: the genes of the virions had a promoter which was regulated by the substance the gene produced. Thus, if there were already sufficient amounts in the body, production was stopped automatically; if there was too little, more was produced. What's more, an excess of a substance could activate other genes producing enzymes which catalyze it. Therefore it was impossible to take an overdose.
In this way the concentration was not simply increased or decreased in the classical brute-force way, but stabilized. The virion ensured that any imbalances were set straight so that the body came closer to a more normal functioning. This also made it possible to target only specific body areas where there were disturbances, which was advantageous, for instance, in the treatment of schizophrenia: schizophrenics have too little dopamine in some brain areas, leading to "negative symptoms" like apathy, and too much dopamine in other areas, leading to "positive symptoms" like delusions. Rather than just decreasing the overall dopamine to control the positive symptoms (which were most dangerous), and in doing so worsening the negative symptoms, synthetic viruses could balance it.
In this way, synthetic viruses could make the functioning of body and mind "normal." Of course, even this could have disadvantages, as our personality is basically a set of abnormalities, so only if it was really needed (as in psychosis), these were applied to the brain. Because the patient of mental illness might actually like some of his symptoms, it was sometimes also possible to only affect some brain areas and rectify those; in other brain areas the virus could either be broken down by substances not present in the targeted brain area, or it could have its genes deactivated by them.
Although a great many of such synthetic organisms were created at first, it was later thought more practical to merge them, or rather their genomes to one. In this way, a universal medicine and at the same time a universal dietary supplement was contrived, and the genus was therefore aptly named Panacea. Later, in addition to affecting substances like proteins, it also affected even larger structures such as organelles and even other bacteria. In this way it was even made to neutralize other pathogens, assisting our own white blood cells.
Panacea had countless functions, and for this reason its genome was also large. However, it had the smallest number of genes it could have while still being viable. Genes it didn't need were removed, so that the genome could still fit in the virion. Based on the Mycoplasma genitalum, which has the smallest known genome (over 500 genes), only the essential genes were included.
As said, by balancing the body's functioning, Panacea made it more normal. Because no-one wanted to be fully normal, however, many of its genes were removed on custom. However, as a dietary supplement it could also optimize it to a supernormal degree, and this was especially so for the brain. Many people choose to be hypomanic, meaning mildly manic, so that they lived much richer lives. Some people also changed their personality from day to day. The morality of this was heavily disputed, however, and most people regarded changing one's personality as wrong. Instead, most people amplified the personality they already had, thus making themselves more emotional or on the contrary more phlegmatic, more sociable or on the contrary more reclusive, more motivated or on the contrary more indifferent.
Because changing one's personality is ego-dystonic, ie not in accordance with one's ego, there were only very few people who experimented with this, and when they did they never let the results be permanent. It was more like a recreational drug, the short-term influence of which can be pleasant but the long-term influence of which can be torture. Some people even used this to temporarily induce mental illnesses, just to know what it feels like, and this was especially done by psychiatrists and relatives of mentally ill people. However, this was nothing new, as drugs had been used for this purpose earlier (eg psychotomimetics, hallucinogens, psychedelics); Panacea was simply a more direct way of doing this, and therefore more safe, and therefore too more often used.