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Lecture 15

BSCI 283 Lecture Notes - Lecture 15: Electroporation, Chitin, Pilus


Department
Biological Sciences Program
Course Code
BSCI 283
Professor
Daniel Stein
Lecture
15

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Gene Transfer in Bacteria 4/5/17
Vertical
o Mother celldaughter cells
Horizontal
o Donor cellrecipient cellnew DNA
Horizontal Gene Transfer
o How bacteria can acquire DNA (new genes, new alleles of genes already present
in bacterial genomes)
o Widespread in bacterialarge role in genomes
o Hard to tell species apart
o Ex. Pathogenic/ lab strain difference in bp
o A major mechanism for spread of antibiotic resistance
o Required for pathogenesis of many microbes
DNA fate
o To repair deletions from external source
o Once inside the new DNA
Restriction
o Restriction enzymes recognize patters on dsDNA and cut the incoming DNA into
pieces
o Defense against foreign DNA
o EcoRI-enzyme from E. coli cuts DNA at pattern GAATTC
o The chromosome will have restriction patterns
Base Methylation
o Older, original DNA strand is modified by methylation. Newer strand lacks
methyl groups
o After replication the DNA is fully methylated by an enzyme: DNA methyl
transferase
Recombination
o If incoming DNA strand is similar to chromosome, it may replicate old sequence
o Sequences must base pair over some of their length for replacement
o Process of homologous regulation mediated by RecA protein
Three Mechanisms
Transformation
o Uptake of DNA found in the environment
o Cells dies and release generic material
o Other cells can then take up free DNA
Co Copetece Mechais
o Natural competence
o Multiple mechanisms
o Some bacteria can take up material through transport mechanism
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