Plasmids Flashcards
What Are The Different Types Of Plasmids?
Resistance (R) Plasmids
Fertility (F) Plasmids
Col Plasmids
Degradative plasmids
Virulence Plasmids
Describe R Plasmids.
Provide Resistance To Toxins/Antibiotics
R-Plasmids:
- Carry 1/more Antibiotic Resistance Genes
- Usually in conjunction with virulence
Determining genes - Often conjugative/mobilizable
- Multiple resistance genes arranged in
Cassettes - Multiple drug resistance (MDR)
- Positive selection in presence of antibiotics
- Used for artificial plasmids
What Do Virulence Plasmids Do?
Convert bacteria Into pathogens
What Do Degradative Plasmids Do?
Allow Metabolism Of Unusual Substances
Mechanism (General):
- Encode Enzymes that break Down Unusual
Compounds, usually Step-By-Step - Convert Compounds Into simpler
Intermediates (e.g. succinate, acetyl-CoA) - Feed end products into central metabolism
(TCA cycle, glycolysis, etc.) - Use specific regulatory genes to Activate
Catabolic Operons only when Target
Compound is present
What Do Col Plasmids Do?
Encode Bacteriocins For Killing Other Bacteria
What Do F Plasmids Do?
Used For Bacterial Conjugation, promote genetic exchange
F-plasmids:
Have 2 Separate Origins of Replication
Divide By Bidirectional Replication when their Host Cell Divides
Divide by rolling circle mechanism when moving from 1 cell to another during conjugation
Why Can’t Col E Plasmids Transfer Themselves From 1 Bacterial Cell To Another?
Because They are Small Plasmids With Less Than 30 genes and are Only Mobilizable
Describe Col Plasmids.
Bind To Outer Membrane Receptors + Gain Access To Inner Membrane/Cytoplasm
Bacteriocins: Reduce Competition In Environment
Colicins: Toxic To E. Coli
Pore Forming Colicins Disrupt Proton Motive Force
Nucleases Digest Genetic Material
Describe Degradative Plasmids.
Able To Digest Variety Of Compounds
Responsible genes Encoded On Plasmid
Describe Pseudomonas TOL plasmid (pWW0)
Degrade Toluene + Xylenes into Acetaldehyde and Pyruvate
Acetaldehyde + Pyruvate fed into TCA Cycle
Describe Virulent Plasmids.
Carry Genes Responsible For Causing Disease In Host
Plasmids Also Enhance Ability To Damage, Invade and Destroy Host Tissues
Mechanism
- Plasmids Encode Virulence Factors
(molecules that help bacteria), which: - Colonize Host (e.g., adhesion proteins)
- Evade/Suppress Immune System (e.g.
Toxins) - Acquire nutrients in Host
- Directly Damage Host Cells
These plasmids do not contribute to core bacterial metabolism like degradative plasmids do—but they’re essential for turning harmless strains into dangerous pathogens.
Describe Ti Plasmid Insertion into GM plants.
- Gene inserted into Plasmid Using
Restriction Enzymes + DNA Ligase - Plasmid introduced into plant cell culture
- T DNA with new gene within Plant
Chromosomes - Plant Regenerates
- New Plant With New Trait Generated
Describe The Yeast Plasmid.
- Used In Genetic Engineering
- Found In The Nucleus Of Most Strains
- Has No Phenotypes
- High Copy Number
Describe Expression Plasmids.
Plasmids used For The Expression of Proteins In Particular Hosts
Purpose:
- To Investigate Function, Enzymes
What Are Plasmid Vectors?
Small, Circular DNA Molecules Engineered to Carry + Propagate Foreign Genes Into Host Cells
Components:
Origin Of Replication: Sequence Recognized by Host’s Replication Machinery
Selectable Markers:
Usually Antibiotic Resistant genes, to allow Bacteria that Take Up Plasmid to Grow Under Selection
Multiple Cloning Sites:
Short Region, Contains Restriction Enzyme Sites
Allows Genes To Be Plugged In By Restriction-Ligation/Other Methods
