MIMM 502

• Honours Mcb/Immunol

• Calendarhttp://www.mcgill.ca/microimm/undergraduate/

courses/mimm502/

• 12 credits

• Info mtg: January 19, 2004, 1200 h

• Sheldon Conference Room: D-1

2005 summer science

• NSERCwww.nserc.ca/sf_e.asp?nav=sfnav&lbi=1_toc

– Undergraduate Summer Research Award– $5000, 4 months May-August– Supervisors in Mcb/Immunol:

• Berghuis, Coulton, Cousineau, Fournier, Matlashewski, Marczynski, Olivier

– Apply in February 05– Awards in April 05

Exchange of genetic information

• Lengeler et al.

• Chapter 16, pp. 386-415• Genetic exchange between microorganisms

bacterial genomes

• Haploid: one copy / cell• Little unused (spacer) DNA• introns

– Rare; DNA seq = colinear with protein seq

• operons– Polycistronic mRNAs – genes related functions

• Sequenced genomes: www.tigr.org

plasmids

• Extra chromosomal DNA– Not physically attached– Circular 2x DNA– ori to replicate autonomously

• Examples– F factors; E. coli 100 kb / 26 genes– Resistance factors = R plasmids– Col factors = colicinogenic / bacteriocins– Virulence factors– Metabolic plasmids

• Specialized metabolic functions• Toluene; PCBs

Acquisition of DNA

• Transformation – Cell acquires DNA from surroundings– No cell-cell contact– No bacteriophages

• Conjugation– DNA transfer: one cell to another– Cell-cell contact

• Transduction– DNA transfer – mediated by bacteriophage

transformation

• Natural transformation– 1944: Principle = DNA

• Streptococcus pneumoniae • Haemophilus influenzae• Bacillus subtilis

• Induced transformation– Competent cells: CaCl2

• E. coli

– Electroporation

natural competence

• Cell secretes low MW proteins

• 2x DNA binds to cell surface receptors

• Cutting DNA with endonucleases– Degrades one strand

• [ssDNA complex + competence-specific proteins]

• Entry of DNA recombination

conjugation

• Donor = F+– Carry F plasmid– Donate F+ to…..

• Recipient = F-

• ~20 genes on F+– synthesis, assembly of F pilus: 1 to 3 per cell– donation of DNA

• tra genestraY, traZ = endonuclease; nick F plasmid

traJ = pilin

• oriTorigin of transfer

outcomes

• Integration of F+ into chromosome Hfr (high frequency recombination); male– tra genes still expressed– Pili: functional

• Hfr strain X F-– Mating pair formation– Rolling circle DNA replication– Transfer

• some genes of bacterial chromosome

– Homologous recombination, replacement

• Different points of insertion of F different Hfr’s

• Different genes transferred to F- recipients

transduction

• Phage mediated transfer of DNA from one bacterial cell to another

• Generalized transduction (T/D)– Strain construction, gene mapping– P1 of E. coli ; P22 of S. typhimurium– Transfer of any segment of chromosome– 2 to 2.5 mins– Frequency of coT/D indicates genes proximity

• Specialized transduction– Lambda (λ) of E. coli– Transfer of only specific segments of bacterial

chromosome– Near site of integration