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Lecture 5: Bacteria, Viruses, Parasites - Coggle Diagram

- - - - Chloroplast in plants
      - Apicoplast in parasites
        
        3 genomes
        
        1 apicoplast genome
        
        1 mitochondrial genome
        
        14 chromosomes
      - Mitochondria
        
        cirular
  - - - Plasmid
        
        present in multiple copies per cell
        
        Do not encode functions essential for growth under all
        conditions
        
        smaller than chromosome
        
        autonomously replicate
        
        Plasmid copy number
        
        Functions
        
        Resistance mechanisms (eg. antibiotics)
        
        Virulence genes
        
        Shigella flexneri
        
        Control of their replication (copy number control)
        
        Metabolic enzymes
        
        Production of antimicrobials (bacteriocins)
        
        Mobility (conjugation) factors
      - Bacteriophage
      - Main chromosome
      - Transposable elements
- - - - direct cell
        to cell contact
      - To initiate, must have
        
        Express proteins required for DNA transfer
        
        – DNA with a region that can begin transfer (origin of transfer oriT)
        
        DNA which encodes a sex pilus
      - Steps
        
        Initial steps
        
        Pilus tip of F+ cell binds to receptor on surface of F- cell
        
        Retraction of pilus brings F+ and F- cells close together
        
        Formation of the conjugative bridge, an opening between the cytoplasm of the two cells
        
        DNA transfer steps
        
        . One strand of DNA is nicked at the oriT site
        (only one of the two DNA strands is cleaved)
        
        One DNA strand is pushed through the
        conjugation bridge
        
        F+ cell repairs plasmid
        
        F- recipient uses incoming DNA as a template
        for DNA synthesis
        
        DNA transfer/synthesis completed and cells
        separate
        
        Both cells are now F+
    - - Transferred via bacteriophage
      - Life cycle of bacteriophage
        
        Lytic Cycle
        
        Lysogenic Cycle
        
        Generalised Transfuction
        
        DNA packaged wrongly
        
        can infect bacteria, but no viable phage
        
        Transferred genes maintained only if can recombine to chromosome
    - - Take up free DNA
      - Antibiotic resistant plasmid
        
        allows selection of the
        recombinant bacteria
        
        used to express genes for purification or
        functional analysis
      - used in many recombinant techniques
        
        plasmid DNA is not easily degraded
        
        plasmids replicate autonomously so genes are expressed without recombination into chromosome
        
        can introduce foreign DNA/genes into cells
      - bacteria must be "competent"
        
        Use CaCl2 to make membrane permeable
        
        electroporation
  - - - intergrate into chromosome
        
        Encode for its own protein
        
        Homologous recombination
      - self replication