Everyone is familiar with the concept of probiotic foods. Medicinal probiotics are an old tradition, dating back to the early days of genetic engineering. Engineered strains of bacteria, viruses, and yeast can do excellent things for ones health, and their potential is still being explored. One of the oldest types of medicinal probitoics are those engineered simply to rid the body of certain unwanted foreign agents; each strain, when ingested or injected, breaks down a drug, sequesters a toxin, or hunts a pathogen.
Medicinal probiotic strains made their way off-Earthone strain at a time. Pre-Fall, there were many, many strains, and no-one felt any great need to preserve them. Families, scientists, refugees and colonists took what strains they thought might be useful with them, while many off-Earth servers containing their genomes were destroyed or suborned by TITANs. Even today, particular strains are the jealously guarded treasure of refugee families, criminal outfits, or brinker communities.
Probiotics counter a specific type of toxin, drug, or pathogen, like an antidote [One cost category higher than their toxin, drug, or pathogen]