UV light, Disinfectants, Antibiotics

UV light is used to control microbial growth Adjacent thymine molecules DNA cross link to form thymine dimer This leads to mutations during the replication of DNA #3 – growth, UV light cannot penetrate plastic.

Disinfectants – antimicrobial agents used on objects – floors. Lysol Antiseptics – antimicrobial agents used on living tissue – mouthwash. Listerine They inactivate enzymes Zone of inhibition – in general larger the zone of inhibition more effective is the antimicrobial agent

Gram negatives are more resistant than gram positives. Substances cannot penetrate the outermembrane.

Antibiotics Made by microbes Purified by the pharmaceutical companies Penicillin Mold – Penicillium notatum Inhibits the formation of peptidoglycan G- - resistant G+ - sensitive

Penicillin – selectively toxic to bacteria. In general, it is not toxic to the host (humans) Humans have no peptidoglycan

Chloramphenicol – Streptomyces Inhibits protein synthesis on the 70S ribosomes High concentrations and prolonged use can cause aplastic anemia Streptomyces Tetracycline, Streptomycin, erythromycin Erythromycin – cannot penetrate the outer membrane

Gentamicin – Micromonospora Inhibits protein synthesis on the 70S ribosomes. Sulfanilamide – synthetic drug Inhibits folic acid synthesis