MICB 201 Lecture Notes - Lecture 8: Streptomycin, Dna Replication, Cell Envelope
Document Summary
Chapter 4: antibiotics and antibiotic resistance in bacteria. Vary in: size (~ 500-1500 daltons, polar and non polar content, charge. Only the cm and the gm -ve om are significant barriers to antibiotic penetration. As chemicals, antibiotics that diffusionally permeate the lipid bilayer of the cm the fastest are expected to: be small, be uncharged, have high nonpolar content/low polar content. All antibiotics whose targets lie in the cytoplasm have significant polar content, most are also charged. Nevertheless, they seem to enter the cytoplasm by diffusing across the cm lipid bilayer. Om lipid bilayer is less fluid than the cm. Most important examples: -lactams: (cid:862)zwitterio(cid:374)i(cid:272)(cid:863) -lactams = both (+) and (-) charges permeate the om faster than those with only (-) or (+) charges, e. g. ampicillin (and amoxicillin) enter more readily than penicillin (or methicillin) May vary due to: antibiotic, target site issues, antibiotic exclusion, antibiotic modification or inactivation, antibiotic efflux.
