MICRB316 Lecture 17: Lecture 17.doc

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Old definition of antibiotics: anything that interfers with bacteria (all antimicrobials) New generation: penecillin (from fungus) was the first new generation antibiotic. Antibitics have been around for a long time. Antibiotic resistance frequently arises following acquisition of new dna carrying abr genes (plasmids, phage, tns) Alternatively, it can arise through activation of a regulatory locus called mar. This alters the expression of multiple genes located on the bacterial chromosome. Produces resistance to antibiotics, organic solvents, oxidative agents, household disinfectants (structurally unrelated). The regulation is comprised of 2 tn units: marc & marrab divergent promoters; marc = inner mb protein unknown function; marr = repressor; mara = activator; marb = small protein, unknown function. In e. coli, marrab is induced by tet, cm (chloramphenicol), salicylate (all have phenolic rings). Under non-inducing conditions, a marr dimer binds 2 direct maro repeats (operator) & represses tn of marrab. [unknown if it has an effect on marc]

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