Bacterial Transformation Plate 27 Bacterial Transformation

Genetic Change Bacterial DNA can undergo changes in several ways: Transformation Conjugation Transduction

Transformation History 1928, a British bacteriologist and medical officer named Frederick Griffith first demonstrated bacterial transformation Streptococcus pneumoniae (AKA “pneumococcus”) can exist in several strains: “S” strain – smooth, encapsulated, deadly “R” strain – rough, unencapsulated, harmless

Griffith’s Experiment Injected mice with the “S” strain of bacteria Result: dead mice Injected mice with the “R” strain of bacteria Result: no sickness or death Injected mice with heat-killed “S” strain of bacteria

Griffith’s Experiment 1. 2. 3.

Griffith’s Experiment 4. Injected mice with a mixture of harmless “R” strain bacteria and heat-killed “S” strain bacteria Result: dead mice

Bacterial Transformation In order for bacterial transformation to occur, there needs to be: “naked DNA”: DNA not found in a cell (“extracellular” DNA) “competent” bacterial cells: ability to take up extracellular DNA

Bacterial Transformation In Griffith’s experiment, segments of the genetic information from the “S” strain bacteria became “naked” when the cells were heat-ruptured

Bacterial Transformation “Competent” bacteria cells take up DNA segments through their cell membranes Some bacteria cells are naturally “competent” Some bacteria cells can become artificially “competent” through chemicals, heat-shocking, and electro-shocking

Bacterial Transformation Enzymes within the cell cut a segment from the newly acquired DNA The segment gets inserted into the cell’s own DNA In Griffith’s experiment, genes from the “S” strain were transferred to the “R” strain, making it harmful

Transformation

What do you think? What kinds of applications can bacterial transformation have? In other words, how can people benefit from the use of this technology?