Lecture 10: Bacterial Variation and Bacterial Mobilome Flashcards
What are the two primary ways that bacterial variation occurs?
Phenotypic variation
Genotypic variation
____: the entirety of all genetic info in an organism - all chromosomes and extrachromosomal elements
____: the complete listing of all genes present in an organism
Genome
Genotype
____: the complete listing of all physical features than an organism expresses
Phenotype
____: A DNA/RNA molecule that controls its own replication and , therefore, is capable of self-duplication
Replicon
____: replicons present in a cell, excluding host cell DNA; includes: plasmids and bacteriophages
Extra Chromosomal Elements
_____: the total of all mobile genetic elements in a genome
Mobilome
Elements that move within a genome (e.g transposons) are the major constituents of the mobilome in ____
A. prokaryotes
B. eukaryotes
B. eukaryotes
In ___, mobile genetic elements that can move between genomes (plasmids and bacteriophages) are also important part of the mobilome
A. prokaryotes
B. eukaryotes
A. prokaryotes
True or False: For any organism, the complete and total potential phenotype is limited to/determined by organism’s genotype
True
_____: the situation in which ALL cells in a POPULATION respond to environmental stimuli in the SAME fashion and produce a new/altered phenotype via: expression of a gene(s)
Is genotypic change needed for this to occur?
Phenotypic variation
No
True or False: Capsule production by Cryptococcus neoformans is an example of phenotypic variation
True
_______: When genome of one or more cells is/are altered
A. Phenotypic Variation
B. Genotypic Variation
B. Genotypic Variation
____: ability of bacteria to detect the size of the own population
Quorum sensing
What are the two ways that genotypic variation occur?
- Mutation (internal change): change in nucleotide sequence
- Horizontal gene transfer (acquisition of gene from external source- from donor to recipient)
True or False: Mutations rarely occur, but since bacteria are found in large populations, net effect can be significant
True
Horizontal gene transfer is also known as _____ and it generates diversity and facilitates spread of advantageous genes
DNA recombination
The horizontal transfer (external acquisition) of genetic material from one bacterial cell (the donor) to another cell (the recipient) can occur by one of three general mechanisms:
1.
2.
3.
- Transformation
- Conjugation
- Transduction
Horizontal genetic transfer and exchange in bacteria involves transfer of either:
1.
2.
3.
- plasmid
- virus
- transposon
____: Uptake of “naked” exogenous DNA (plasmid or portion of chromosome fragment) by recipient cell
A. Transformation
B. Transduction
C. Translation
A. Transformation
The ____ cell chromosomal genes encode for the mechanism of transformation
A. Donor Cell
B. Recipient Cell
B. Recipient Cell
For transformation to occur, which cell must be in a state of competence (meaning ready to acquire naked DNA)
A. recipient cell
B. donor cell
A. recipient cell
In transformation, the ___ cell lyses, releasing DNA
A. Donor Cell
B. Recipient Cell
A. Donor Cell
What are the two limitations of Transformation?
- Not all bacterial genomes are competent
- Need a chromosomal segment for integration/recombination to occur - plasmid DNA does not require this though
What is the significance of conjugation and transformation?
Results in the transfer of antibiotic resistance and virulence factors among bacteria
___: Horizontal gene transfer of DNA from donor bacterial cell to a recipient bacterial cell via a mechanism encoded by a conjugative (transmissible) plasmid present in donor cell; it involves CELL TO CELL contact
A. Conjugation
B. Translation
C. Transformation
A. Conjugation
True or False: Cell to cell contact is essential in conjugation
True
True or False: During conjugation, a RNA copy of the conjugative plasmid is transferred from donor to recipient cell during plasma RNA replication
False - DNA
During conjugation, both single stranded DNA strands (in mom and daughter cell) are made ____ and process is complete
double stranded
What is a limitation for conjugation?
Conjugative plasmids have host ranges
____: the horizontal transfer of genetic information (chromosomal or plasmid DNA) from one bacterium to another via bacteriophage (bacterial virus)
Transduction
What are the two types of phages?
- The lytic (virulent) phage
- The temperate phage
___ infects bacterial host cell, replicates, then kills the bacterium (via: lysis), thereby releasing new progeny to infect other cells
A. The lytic (virulent) phage
B. The temperate phage
A. The lytic (virulent) phage
_____ infects host cell. However, after it enters cytoplasms of host cell, it has two options:
1. go through normal lytic cycle
2. become latent virus (prophage) - replicates in synchrony with bacterial DNA and is passed to daughter cells.
From here, phage can either a) remain in cytoplasm or b) integrate into the bacterial chromosome
A. The lytic (virulent) phage
B. The temperate phage
B. The temperate phage
The latent virus (prophage) will do one of which two things?
1.
2.
- Remain in cytoplasm
- Reintegrate/insert into host cell DNA
True or False: The latent virus will always lead prophage DNA to replicate in synchrony with host cell DNA, leading it to it being passed onto daughter cells
True
Antigenic variation of Type IV pilus of N.gonnorhoea: from silent loci to express loci is an example of ____
phenotypic variation
True or False: Transformation, acceptance of DNA from donor is not specific
True
True or False: For transformation, the donor’s DNA can be chromosomal or plasmid, but must be free/naked DNA
True
True or False: In conjugation, contact
between donor and
recipient is not required
False - it IS required!
In conjugation, transfer of a
conjugative plasmid,
start from the ____ end
of the nicked DN
A. 5’ end
B. 3’ end
A. 5’ end
In conjugation, transfer of ‘nick DNA’ occurs during ____
DNA replication
True or False: In conjugation, both ssDNA strands (from donor and
recipient cell) remain single stranded!
False - are made dsDNA
True or False: There is specific host range for conjugative plasmid
True
If possessing latent phage, the
bacterial cell is said to be _____
lysogenized
What are the two types of transduction?
- Generalized
- Specialized
True or False: Generalized transduction is mediated by both lytic and temperate bacteriophage
True
Why are ALL donor genes equally likely to be transferred/transduced
during generalized transduction?
Host chromosome is broken down into fragments
Random fragment of bacterial DNA is accidentally encapsulated in a phage protein coat. This best describes which type of transduction:
A. Generalized Transduction
B. Specific Transduction
A. Generalized Transduction
In generalized transduction, all regions of the bacterial chromosome can be transduced, but only bacterial _____ (no phage DNA!!) will be in transducing particles
chromosomal DNA
True or False: Transfer of drug resistance in Staphylo is an example of generalized transduction
True
Prophage integrates into bacterial chromosome and, occasionally, prophage DNA is incorrectly excised, taking adjoining specific bacterial DNA with it.
This best explains:
A. Generalized Transduction
B. Specialized Transduction
B. Specialized Transduction
In specialized transduction, the transducing particles carry both host ___ DNA and ___ DNA
host chromosomal DNA; phage DNA
True or False: In both generalized and specialized transduction, the recombinants have the same genotype from both the donor and recipient
False - in both cases, they have a genotype that is UNALIKE both donor or recipient
In ____, transducing phage infects new host cell (after phage replicants) where recombinant (cross over) can occur
A. Generalized Transduction
B. Specialized Transduction
C. Both generalized and specialized transduction
C. Both generalized and specialized transduction