Chapter 5: Bacterial Transformation and Polymerase Chain Reaction

what is the clinical significance of bacterial transformation in biotech?

it explains antibiotic resistance spread, enables genetic engineering for insulin production, and underlies gene therapy vectors

when did Griffith discover transformation?

1928

how did the mouse die in station 1?

S-stain injected into mouse causes pneumonia

what did the S-strain contain?

polysaccharide capsule enabling immune evasion

how was the R-strain different from the S-strain?

R-strain lacks a capsule

what happened in station-3 of Griffith’s experiment?

• heat killed S-strain injected into mouse

• mouse survives

what happened in station 4?

• heat killed S-strain + live R-strain injected into mouse

• mouse dies (from pneumonia caused by live S-strain)

how did the bacteria demonstrate genetic variation?

what happens during DNA release and uptake in the transformation process?

• S chromosome released from heat killed bacteria contains capsule gene

• recipient bacterium w R chromosome incorporates foreign DNA thru cell membrane

• competent bacteria express surface receptors for DNA uptake

what happens during DNA integration?

• nucleases degrade 1 DNA strand

• complementary strand integrates via homologous recombination

• integrated S DNA replaces homologous region of R chromosome

what happens during Bact. division in the transformation process?

• dividing bacteria replicates hybrid chromosome containing S strain capsule gene

• daughter cells inherit transformed genotype w capsule synthesis ability

• capsule production in offspring creates disease —> producing S strain from harmless R strain

what is the clinical significance of Bact conjugation?

• antibiotic resistance

• enables horizontal gene transfer

what are the different bacterial mating types?

• F+ bacteria (genetic donor)

• F+ chromosome

• F- bacteria (genetic recipient)

• F- chromosome

what is the Fertility Factor?

episomal DNA conferring donor ability

what is the conjugation bridge?

F factor genes creates bridge between cells

• encodes for Pilus

how are genes transferred during conjugation?

through the sex pilus

what is high frequency recombination?

what is bacterial transduction?

enables Bacteriophage to transfer genetic material between bact

what happens during Bacteriophage attachment?

• bacteriophage recognizes specific receptor sites on bacterial surface

• bacteria wall provides attachment site for phage tail fibers

what happens during phage DNA replication?

what happens during packaging and phage release?

• Aberrant packaging- bacterial DNA segments are mistakenly packaged

what are the steps of generalized transduction?

1) bacteriophage attachment

2) DNA injection and fragmentation

3) phage DNA replication

4) packaging error and phage release

what happens during prophase integration and excision?

• donor Bact. harbors integrates Prophase DNA within chromo

• donor Bact. includes phage & adjacent Bact genes

• template phage integrates at specific attachment sites in bacterial chromosome

what is hybrid DNA formation?

• hybrid DNA contains partial phage genome fused with specific bacterial genes

• defective phage lackes complete viral genome but retains packaging signals

how is DNA transferred to recipient?

• phage infection

• recombinant bact undergoes homologous recombination w incoming DNA

• hybrid DNA integrates via site-specific recombination at homologous sequences

what is the pre-integration state?

• host bacteria contains recipient chromosome prior to integration

what is the post-integration state?

• homologous recomb integrates donor DNA into host chromosome

what is the clinical significance of Bact Transduction?

• mediates virulence factor transfer

• enables rapid dissemination of antibiotic resistance genes