BT3: Intro to bacteriology 3 Flashcards
What are the main features of bacterial genome?
1 single circular chromosome of ds DNA
Can have plasmids
DNA is supercoiled
Have core & accessory genome
How is bacterial genome different from eukaryotic genome?
Bacterial genome is smaller than eukaryotic genome.
Bacterial genome is haploid while eukaryotic genome is diploid.
Bacterial genome consists of a single chromosome while eukaryotic genome consists of multiple chromosomes.
Bacterial genome is circular while eukaryotic genome is linear.
Bacterial genome can have plasmids while eukaryotic genome does not.
Bacterial genome has higher coding density than eukaryotic genome.
Bacterial genome has operons while eukaryotic genome does not.
Bacterial genome does not have introns & exons while eukaryotic genome does.
What is the core bacterial genome?
Genes that are present in all strains of a bacteria species and necessary for bacterial survival.
What is the accessory bacterial genome?
Genes that are present only in certain bacterial strains or a subset of strains that are not essential for bacterial survival.
What is the pangenome?
The core and all the accessory genes of a bacterial species together.
What are the 3 main methods of genetic change?
- Single Point Nucleotide mutations
- Insertions/deletions
- Horizontal gene transfer
What are the 3 methods of horizontal gene transfer?
- Phage transduction
- Transformation
- Conjugation
How does phage transduction (HGT)?
1) Phage attaches to a bacteria and injects its DNA.
2) Phage DNA gets integrated into bacterial DNA.
3) Phage replication is induced.
4) Bacteria lyses and phage is released.
How does phage transduction lead to genetic change?
The phage can take DNA from a bacteria and pass it to other bacteria.
What is special about lytic phages?
They don’t integrate their DNA in the bacterial DNA, they just replicate straight away.
How does transformation (HGT) occur?
1) Free linear DNA binds to the bacterium and is taken in to the bacterial cell.
2) DNA can be integrated into the chromosome randomly/by site-specific or homologous recombination/existing as a plasmid.
What is conjugation (HGT)?
A mechanism of gene transfer that requires cell-cell contact encoded by plasmids.
What are the donor and recipient cells in conjugation (HGT)?
Donor cell contains the conjugative plasmid and will induce conjugation. Recipient cell does not have the plasmid.
What is the process for conjugation (HGT)?
1) Plasmid encodes for the expression of sex pilus (F).
2) Pilus allows cell-cell contact between donor & recipient cells.
3) Plasmid replicates & the replicated copy ends up in the recipient cell.
What is the rolling circle replication of plasmid?
It’s when the plasmid replicates and at the same time rolls to end up in the recipient cell.
What is intrinsic antimicrobial resistance?
When a bacterial strain has the resistance naturally.
What is acquired antimicrobial resistance?
When a bacteria acquires resistance through mutations.
What are the 4 main methods of antimicrobial resistance?
- Modified/replaced/overproduced target
- Reducing drug uptake
- Increasing drug efflux
- Drug inactivation/modification
What happens to a bacteria when it senses iron availability?
When a lot of iron is present, iron binds to the promoter region of a gene so the gene is essentially not transcribed.
When not much iron is present, RNA polymerase can bind to the promoter region of the gene and it can produce a protein that will increase iron uptake.
How does a two-component signal transduction system work?
There is one component that is attached to the membrane. A phosphorelay will transmit a signal that will bind to DNA to initiate/regulate transcription of certain genes.
What is the purpose of quorum sensing?
It gives information to the bacteria about its location.
How does quorum sensing work?
It relies on the bacteria’s ability to sense biochemical compounds produced by other bacteria to measure bacterial density around the bacteria.
