Download
1 / 8
80 likes | 215 Vues
This overview discusses the roles of UV light, disinfectants, and antibiotics in controlling microbial growth. UV light disrupts DNA by causing thymine dimers, leading to mutations. Disinfectants, such as Lysol, target surfaces, while antiseptics, like Listerine, act on living tissue. The effectiveness of antimicrobial agents is measured by the zone of inhibition, influenced by the resistance of gram-negative bacteria. Antibiotics, produced by microbes and purified by pharmaceutical companies, target bacterial structures like peptidoglycan, demonstrating selective toxicity, particularly with agents like penicillin and chloramphenicol.
E N D
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
