 |
P. s. pv. tomato DC3000 | P. s. pv.phaseolicola 1448A | ||
 |
Module
2 - Home Page Gene Transfer and the Creation of Pathogens |
|||
|
Additional Resources: Student
Resources |
Glossary
of Terms (for CAPITALIZED words) |
Gene Transfer Fact Sheet:
In order to cause disease, bacteria must carry genes that encode the necessary virulence proteins. Some of the different ways that bacteria can acquire new genes are described below.
Animals repreoduce sexually:
- offspring are unlike either parent
- genetic information from both parents is combined and rearranged (called recombination) to create a novel organism.
- this strategy maintains diversity in the gene pool
- animals reproduce at a slow rate and sexual reproduction enables individual species to face different selective pressures.
SEXUAL REPRODUCTION
The Simpsons (c) Fox Broadcasting Corporation
In contrast, bacteria reproduced by binary fission:
- new cells are identical to the parent
- genetic information in the new cells is the same as in the original cell
- diversity in the gene pool is maintained by mutation, recombination within the individual cell, and the exchange of genetic information between bacteria (the subject of this module) rather than sexual recombination
- bacteria reproduce at a high rate so new traits can quickly be selected for
BINARY FISSIONHORIZONTAL GENE TRANSFER by CONJUGATION
HORIZONTAL GENE TRANSFER (HGT):
- the transfer of a small piece of DNA from one bacterium to another
(NOT sexual reproduction)- can occur by:
- CONJUGATION or Bacterial Mating - where two bacteria in close proximity exchange a piece of DNA through a hollow tube-like structure called a pilus.
- TRANSFORMATION- when a bacterium picks up a piece of DNA from its surroundings that is left over after another cell has died.
- TRANSDUCTION - when a virus infects a bacterium (yes! bacteria get viruses too) and picks up some of the bacteria's DNA. This virus then takes that piece of DNA with it when it infects another bacterial cell
In this module you'll:
Learn how bacteria transfer genes from one to another Learn more about antibiotic resistance genes and how you can help stop their transfer from resistant to non-resistant bacteria Learn about how scientists approach new puzzles by thinking of a possible explanation or "hypothesis" and designing experiments to test it Explore Koch's Postulates, pathogenesis and degress of proof
