Bacterial Genetics Flashcards
How do bacteria differ from Eukaryotes?
Bacteria have circular DNA, no compartments, contain plasmids, and supercoiling of DNA. Single origin of replication.
How is transcription and translation different in bacteria?
Bacteria contain operons without introns/exons and a single RNA Polymerase that begins translation as transcription is happening.
What are the differences in Ribosomes in Eukaryotes and Bacterium?
Bacteria have 30S and 50S subunits to make a 70S subunit
How do bacteria divide and become diverse?
Bacteria divide via binary fission and frequently has replication errors due to limited error checking, which can introduce advantageous mutations. Also can horizontally transfer genetic material.
What are the three kinds of transfer of genetic material that is important for virulence factors and resistance?
Plasmid
Insertion/Transposons
Pathogenicity Islands
What are plasmids and how can they transfer?
Plasmids are miniature chromosomes that replicate independently, which are smaller. Considered transformation when transferred.
What is a insertion sequence/transposon?
A segment of DNA that is typically located on plasmids or bacteriophages that possess inverted terminal repeats and encode Transposases that recognize the repeats and cut the DNA allowing it to move to another location (within genome or another organism).
What are the benefits of transposons?
They often have Abx resistance encoded allowing that gene to be transferred amongst microbes easily.
What are the different types of transposons?
- Insertion sequences with inverted repeats on the ends and transposase between.
- Composite transposases with two inverted sequences on each end with a toxin/resistance gene between. Allowing the entire piece to be mobile
- TnA Family - same as composite, except has a transposase regulator
- Insertion sequence can be found on bacteriophages as well.
How can insertion sequences regulate virulence factors?
Insertion sequences can promote downstream expression and certain ones have site specific inversion that can alternate phases in the two directions, essentially turning off and on the downstream genes.
Ex. Fimbriae - attachment vs No Fimbriae - avoids detection
What is a pathogenicity island?
A large segment of bacterial DNA that possess a variety of gene products located on plasmid or bacteriophage.
– unable to replicate themselves –
What are the three ways of transfer of DNA?
Transformation - from environment
Conjugation - direct contact
Transduction - bacteriophage
How does conjugation work?
Direct binding of bacterium via mating pilius, donation bacterium copies DNA to transfer and keeps original copy. Can transfer everything from plasmid, transponsons, and pathogenicity islands.
What are the differences between lytic and lysogenic phases of transduction (bacteriophages)?
Lytic is where the bacteriophage reproduce themselves independent of host genome causing lysis.
Lysogenic is where the bacteriophage integrate their DNA into the host, then it is replicated each time a hosts is.
How do the bacteriophages transduce DNA?
When phage DNA is injected into a cell it creates more phages and lysis the DNA, then all the phages package that cell’s DNA and they are released and can insert that DNA into another cell.
