Bacterial Genetics

Bacterial Genetics • Underlying factors that predispose organisms to changes • Transduction • Transformation • Conjugation The effects of genetic changes: antmicrobial resistance   change in biochemical profiles

Bacterial genetic material • Chromosome : one unique chromosome whch encodes upto 4000 separate genes • Plasmid :extra chromosomal DNA molecules which encode 40-50 genes • Transposons: DNA with two insertion sequences(IS) on its sides

DNA Transfer between bacteria Three basic mechanisms : • Conjugation • Transformation • Transduction

Transferable Resistance(horizontal gene transfer) • Plasmids : independently replicating DNA molecules outside bacterial chromosome • Transposons : Discrete DNA sequences capable of translocation from one replicon to another – ‘jumping genes’

Extrachromosomal or Transferable • Conjugation • Transformation • Transduction

Transformation Transformation Transfer of genetic material from the environment • Before recipient cells can take up DNA they must be competent –certain physiological state that allows DNA to enter through receptor sites

Transduction

Molecular Genetics of Antibiotic Resistance • Inherent Resistance • Acquired Resistance Mutational

Transferable Plasmids Transposons

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What does not kill them makes them stronger !

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Resistant Strains Rare

Antimicrobial Exposure

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Resistant Strains Dominant

Emergence of Antimicrobial Resistance Susceptible Bacteria Resistant Bacteria Mutations

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Resistance Gene Transfer New Resistant Bacteria