14.3 Chemotherapy cures the host by killing the disease The use of drugs that destroy disease-causing agents without destroying the animal host is known as chemotherapy. It works by taking advantage of the ways a disease-causing agent, also known as a pathogen(病原体), is different from a host · Sulfa drugs(磺胺类药物) and antibiotics(抗生素) treat bacteria infections Humans can use folic acid(+ )from outside sources, but bacte have to synthesize from PABA BN○ C-OH H Several steps PABA OH OH N C-N-C-CH, CH-C N H H HH Bacterial enzyme H,NN Folic acid Fig 14.6 bacterial enzymes use para-aminobenzoic acid(PABa)to synthesize folic acid14.3 Chemotherapy cures the host by killing the disease • The use of drugs that destroy disease-causing agents without destroying the animal host is known as chemotherapy. It works by taking advantage of the ways a disease-causing agent, also known as a pathogen (病原体), is different from a host. • Sulfa drugs （磺胺类药物） and antibiotics （抗生素）treat bacteria infections • Humans can use folic acid (叶酸) from outside sources, but bacteria have to synthesize from PABA. PABA Folic acid Several steps Bacterial enzyme Fig 14.6 bacterial enzymes use para-aminobenzoic acid (PABA) to synthesize folic acid