A surprisingly large number of everyday medications originally come from bacteria and fungi. Roughly 5% of all FDA-approved drugs are natural products used in unmodified form, and many more are chemically tweaked versions of compounds first discovered in microbes. The list spans antibiotics, cholesterol drugs, cancer treatments, immunosuppressants, and even cosmetic injectables. Here’s a practical breakdown of the major drug categories and the organisms behind them.
Antibiotics From Fungi
Penicillin is the most famous example. Alexander Fleming noticed in 1928 that a Penicillium mold killed bacteria on a petri dish. His original mold was later reclassified as Penicillium notatum, but the strain that made mass production possible was Penicillium chrysogenum, found growing on a moldy cantaloupe at a market in Peoria, Illinois. That grocery store mold produced six times more penicillin than Fleming’s original and became the foundation for large-scale manufacturing during World War II.
Penicillin opened the floodgates. Through the 1940s and 1950s, researchers used similar discovery techniques to find streptomycin, chloramphenicol, erythromycin, vancomycin, and dozens of other antibiotics. Some came from fungi, others from soil bacteria, and the success rate was so high that scientists coined the word “antibiotics” to describe this new class of drugs.
Antibiotics From Bacteria
Soil-dwelling bacteria in the genus Streptomyces are the single most productive source of antibiotics ever found. About two-thirds of all microbial antibiotics come from a group called actinomycetes, and roughly 80% of those trace back to Streptomyces species specifically. The list of drugs they produce reads like a pharmacy shelf:
- Streptomycin, from S. griseus, was the first effective treatment for tuberculosis.
- Tetracycline, from S. aureofaciens, is still widely prescribed for acne, respiratory infections, and Lyme disease.
- Erythromycin and azithromycin (the “Z-pack”) belong to the macrolide class, originally derived from Streptomyces species.
- Vancomycin, a glycopeptide antibiotic, is often considered a last-resort drug for serious resistant infections like MRSA.
- Chloramphenicol, from S. venezuelae, treats severe eye and ear infections.
- Gentamicin, neomycin, and kanamycin are aminoglycoside antibiotics from various Streptomyces species.
- Daptomycin, also from Streptomyces, was approved by the FDA in 2003 for complicated skin infections.
These antibiotics work by targeting different weak points in bacterial cells. Some, like the penicillins and vancomycin, prevent bacteria from building their protective cell walls. Others, like erythromycin and tetracycline, block the cellular machinery bacteria use to make proteins. A third group, including rifampicin, interferes with how bacteria copy their DNA, stopping them from reproducing.
Antifungal Drugs From Bacteria
In an interesting twist, one of the most important drugs for treating fungal infections also comes from bacteria. Amphotericin B is produced by Streptomyces nodosus and has been used in clinical practice for over 50 years. It remains the preferred drug for deep, life-threatening fungal infections. Over 80% of natural antibacterial and antifungal drugs originate from bacterial sources, showing how effectively we’ve turned microbes against each other.
Cholesterol Drugs From Fungi
Statins, the most widely prescribed cholesterol-lowering medications in the world, have fungal origins. The first statin to reach the FDA was lovastatin, produced by fermenting the mold Aspergillus terreus. An earlier compound called compactin was discovered in 1973 from Penicillium citrinum, the same genus that gave us penicillin.
These fungal compounds work by blocking a specific enzyme your liver needs to manufacture cholesterol. By competing with the enzyme’s natural substrate, statins slow down your body’s cholesterol production. They also reduce cholesterol buildup in the liver, which has secondary benefits like lowering the risk of gallstone formation. Modern statins like atorvastatin and rosuvastatin are synthetic, but their design is directly based on the molecular structure of those original fungal metabolites.
Immunosuppressants From Fungi
Organ transplantation became far more successful thanks to a compound isolated from an insect-killing fungus. Cyclosporine was first extracted from Tolypocladium inflatum in the early 1970s and approved as an immunosuppressant in 1983. It calms the immune system enough to prevent the body from rejecting a transplanted organ, and it transformed the survival rates for kidney, liver, and heart transplants. More than 30 analogs of cyclosporine have since been identified, some with antiviral or antiparasitic properties.
Cancer Treatments From Bacteria
Streptomyces species produce several frontline cancer drugs. Doxorubicin, one of the most widely used chemotherapy agents in the world, comes from this bacterial genus. So does bleomycin, used to treat lymphomas and testicular cancer, and actinomycin D, used in certain childhood cancers. These compounds fight cancer through multiple routes: triggering programmed cell death, cutting off the blood supply tumors need to grow, and disrupting the signaling pathways cancer cells hijack to keep multiplying.
Botulinum Toxin From Bacteria
Botox is produced by Clostridium botulinum, an oxygen-avoiding bacterium best known for causing botulism food poisoning. In tiny, controlled doses, the same toxin has legitimate medical applications that go well beyond smoothing wrinkles. An ophthalmologist named Alan Scott pioneered its medical use in 1981 to treat crossed eyes (strabismus). Today, botulinum toxin injections are the treatment of choice for focal dystonias like torticollis (involuntary neck twisting) and writer’s cramp, as well as hemifacial spasm. They also help manage spasticity, chronic anal fissure, a swallowing disorder called achalasia, and excessive sweating.
Human Insulin From Engineered Bacteria
Not all microbial drugs rely on compounds that bacteria or fungi make naturally. In the late 1970s, scientists figured out how to insert the human gene for insulin into E. coli bacteria, essentially turning them into tiny insulin factories. The process involved chemically synthesizing the genes for insulin’s two protein chains, inserting each into a separate strain of E. coli, growing the bacteria, harvesting the insulin chains, and then joining them together through a chemical reaction. The result, called Humulin, became the first recombinant DNA drug approved for human use. Before this, people with diabetes relied on insulin extracted from pig or cow pancreases, which sometimes caused allergic reactions. The same basic technique was used to produce human growth hormone in bacteria.
Why Microbes Make So Many Drugs
Bacteria and fungi have been waging chemical warfare against each other for billions of years. The antibiotics, toxins, and other compounds they produce are essentially weapons, designed to kill competing organisms or defend territory in soil, water, and decaying matter. Pharmaceutical science has spent the last century intercepting those weapons and repurposing them for human medicine.
Most of these discoveries came from culturable organisms, the ones that grow easily in a lab. But the vast majority of soil microbes can’t be grown using standard techniques, which means the chemical library hidden in uncultured species is largely untapped. In 2015, researchers used a device called the iChip to grow previously unculturable soil bacteria and discovered teixobactin, a new antibiotic that kills gram-positive bacteria and tuberculosis, including drug-resistant strains. Because teixobactin targets a part of bacterial cell architecture that is highly conserved and difficult to mutate, resistance is expected to develop very slowly if at all. That discovery suggests the next generation of microbial drugs may come from organisms we’re only now learning how to study.