L32: Microbial Genetics

• properties of the bacterial genome

  A) fimbrae

  B) nucleoid

  C) ribosomes

  D) plasma membrane

  E) cell wall

  F) capsule

  G) flagella

  H) plasmid

  I) cytosol

  J) bacterial chromosome

  
• a bacterial genome is a single circular chromosome
• a bacterial genome has no nuclear membrane. however the chromosome is restricted to the defined region of the bacterial cell known as the nucleoid
• in bacterial genome, other small circular self-replicating DNA molecules can be found in the cytosol, these are known as plasmids
• gene transfer is vertical and horizontal
• horizontal gene transfer is directly from one organism to another
• vertical gene transfer is from parent to offspring
• if we inject live cells in a capsule to an organism, the mouse dies
• if we inject heat-treated dead cells in an organism, the mouse lives
• if we inject strain R live cells (no capsule) in an organism, the mouse lives
• virulence factors help bacteria survive in the host, sometimes at a cost to the host. a good example are the capsules
• antibiotic resistance reduce the effectiveness of antibiotics against the targeted bacteria. a good example is the plasmid carrying beta-lactamase enzyme which inactivates penicillin
• in horizontal transfer, the 3 strategies are: transformation, transduction and conjugation
• transformation involves the uptake of short fragments of naked dna by naturally transformable bacteria
• transduction involves transfer of DNA from one bacterium to another via bacteriophages
• conugation involves transfer of DNA material via sexual pilus and requires cell-to-cell contact
• phage therapy is the therapeutic use of bacteriophages to treat pathogenic bacterial infections
• conjugation is direct transfer of genes between bacteria through a conjugation tube
• transduction, the dna is transmitted from one cell to another. newly acquired DNA is incorporated into the genome of the receiver