Learning Objective

Describe the types of genetic material found in bacteria, including chromosomal DNA, plasmid DNA, and bacteriophage (prophage) DNA, and explain their roles in bacterial function, adaptation, and virulence.

Chromosomal DNA

• Large, circular, double-stranded DNA.
• Contains essential genes for survival, metabolism, and replication.
• Located in the nucleoid, with no nuclear membrane.
• Typically, one chromosome → haploid.

Plasmid DNA

• Small, circular, double-stranded DNA.
• Replicates independently.
• Encodes non-essential but advantageous traits:
  • Antibiotic resistance
  • Toxins
  • Fertility (F plasmid)

• Moves between bacteria via conjugation.

Bacteriophage DNA (Prophage)

• Viral DNA is integrated into the bacterial chromosome.
• From lysogenic phages.
• Can encode virulence factors → lysogenic conversion.
  Examples: Diphtheria toxin, Cholera toxin, Botulinum toxin.

Activity