MIMM 502 Honours Mcb/Immunol Calendar courses/mimm502/ 12 credits Info mtg: January 19, 2004, 1200 h Sheldon Conference Room: D-1

2005 summer science NSERC –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 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:

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: CaCl 2 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 genes traY, traZ = endonuclease; nick F plasmid traJ = pilin oriT origin 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