BM1000 Lecture Notes - Lecture 30: Horizontal Gene Transfer, Plasmid, Chromosome
Document Summary
Typically consists of single, circular molecule of dna, Part of donor dna inserted onto chromosome of recipient. Occurs in less than 1% of a population. A recipient cell takes up dna from the environment. Due to alterations in cell wall & cytoplasmic membrane. Transfer of dna from one cell to another via a replicating virus. Phage attaches to host cell & injects dna. Direct contact via pilus between two conjugating bacteria. Carry genes not essential for growth, metabolism or reproduction. May be present in multiple copies per cell. Both cells end up with copies of the plasmid. When plasmid excises - some chromosomal dna is also excised & transferred to next c. May carry genes for proteins that inactivate antibiotics or effect uptake into cell. Genes are often carried on transposable elements in plasmids. Proteins toxic to other bacteria lacking the same plasmid. Plasmids may carry genes for proteins involved in bacterial attachment and colonisatio.
