These derivatives are also components in antibiotics such as echinomycin and actinomycin. In his doctoral work, he discovered the antibiotics actinomycin and streptothricin. Streptomycin, actinomycin, and streptothricin are all medically important antibiotics isolated from Actinomycetes bacteria. He also developed the fermentation processes for actinomycin, vitamin B, streptomycin, and penicillin. Anti-rejection medication after the operation included actinomycin C, corticosteroids and x-ray irradiation. Actinomycin D was the first antibiotic shown to have anti-cancer activity. Actinomycin is a vesicant, if extravasation occurs. Actinomycin is also known to display antifungal properties. In cell biology, actinomycin D is shown to have the ability to inhibit transcription. Actinomycin is a complex molecule that intercalates DNA and prevents RNA synthesis.