T4SS || ERRORLESS SOLUTIONS 100%.
What are the different roles of T4SS in bacteria? correct answers 1. Bacterial conjugation - the
unidirectional transfer of DNA from donor bacteria to recipient
2. DNA release into extracellular space
3. DNA uptake of single stranded and double stranded DNA from the cytosol
4. Important for effector molecule translocation - deliver effector molecules to a wide variety of
target cells - inject the proteins, gene transfer of the proteins, toxin secretion, non-lytic release
from protozoan host - after being exposed to particular environment cues, triggers
release/injection of toxins from the vacuole to the intracellular space of eukaryotic cell.
Give examples of uses of T4SS correct answers Legionella lives in LCV
At a given point secretes ~300 different factors that hijack specific pathways of the eukaryotic
cell - bacterial survival
Bacterial killing - responsible for injecting effectors via minimised T4SS
What are the general routes of horizontal gene transfer? correct answers 1. Tranduction - process
by which virus transfers genetic material from one bacterial to another through phages which
incapsulates and inject DNA into target cell
2.Conjugation - donor and recipient cells are connected through a channel called a pillus and
through this the DNA is travelling from the donor to the recipient
3. Transformation - bacteria takes up DNA floating in environment
4. Outer membrane vesicles - where DNA is encapsulated into these vesicles that are shed off
from the bacteria and then fused into the target cell
What bacterial species undergo T4SS? correct answers T4SS mediates conjugation mainly in
gram negative bacteria but gram positive also encode the secretion system - understudied due to
thick peptidoglycan layer of the envelope,
Some gram +Ve include streptomyces, streptococcus
Prevalence suggests it is advantageous to the species - how?
Usually transfers plasmids, rather than chromosome
, How does T4SS work? correct answers Transfer of plasmids rather than chromosome
1. Plasmid dsDNA nicked by relaxosome - main function of relaxosome is to unwind the double
stranded plasmid to single stranded by using relaxase enzyme that nicks and unwinds dsDNA
2. ssDNA/VirD2 export through conjugation pilus
3. Conjugation ssDNA is circularised and replicated to dsDNA plasmid in the recipient cell and
becomes a plasmid
4. Forms replicated plasmid - the recipient becomes donor itself
What is the Fertility Factor (F plasmid)? correct answers The F factor is present in strains that are
able to transfer genes by conjugation
Have the ability to donate ability
Can be lost and regained easily
Strains carrying F are donors and designated F+
Strains lacking F are recipients and designated F-
F is a conjugative plasmid which encodes the machinery for conjugation
Currently the only T4SS known that can dynamically extend and retract
What is the minimised type IV secretion system? correct answers This is encoded in small
plasmids (<20kb) or genomic islands following prototypical VirB genetic organisation
It is capable of mobilising ssDNA (small plasmids) or protein toxins
Shorter pilus that was thought to be made of cyclic pilins (not true)
Structurally organised in four main sub-assemblies: conjugative pilus, outer-membrane core
complex (OMCC), IM complex and energy centre (VirB4, VirB11 and VirD4 ATPases)
This system is leveraged for bacterial killing
What is the composition of the minimised T4SS? correct answers Has ~12 subunits to be built
VirB1-B11 + VirD4
What are the different roles of T4SS in bacteria? correct answers 1. Bacterial conjugation - the
unidirectional transfer of DNA from donor bacteria to recipient
2. DNA release into extracellular space
3. DNA uptake of single stranded and double stranded DNA from the cytosol
4. Important for effector molecule translocation - deliver effector molecules to a wide variety of
target cells - inject the proteins, gene transfer of the proteins, toxin secretion, non-lytic release
from protozoan host - after being exposed to particular environment cues, triggers
release/injection of toxins from the vacuole to the intracellular space of eukaryotic cell.
Give examples of uses of T4SS correct answers Legionella lives in LCV
At a given point secretes ~300 different factors that hijack specific pathways of the eukaryotic
cell - bacterial survival
Bacterial killing - responsible for injecting effectors via minimised T4SS
What are the general routes of horizontal gene transfer? correct answers 1. Tranduction - process
by which virus transfers genetic material from one bacterial to another through phages which
incapsulates and inject DNA into target cell
2.Conjugation - donor and recipient cells are connected through a channel called a pillus and
through this the DNA is travelling from the donor to the recipient
3. Transformation - bacteria takes up DNA floating in environment
4. Outer membrane vesicles - where DNA is encapsulated into these vesicles that are shed off
from the bacteria and then fused into the target cell
What bacterial species undergo T4SS? correct answers T4SS mediates conjugation mainly in
gram negative bacteria but gram positive also encode the secretion system - understudied due to
thick peptidoglycan layer of the envelope,
Some gram +Ve include streptomyces, streptococcus
Prevalence suggests it is advantageous to the species - how?
Usually transfers plasmids, rather than chromosome
, How does T4SS work? correct answers Transfer of plasmids rather than chromosome
1. Plasmid dsDNA nicked by relaxosome - main function of relaxosome is to unwind the double
stranded plasmid to single stranded by using relaxase enzyme that nicks and unwinds dsDNA
2. ssDNA/VirD2 export through conjugation pilus
3. Conjugation ssDNA is circularised and replicated to dsDNA plasmid in the recipient cell and
becomes a plasmid
4. Forms replicated plasmid - the recipient becomes donor itself
What is the Fertility Factor (F plasmid)? correct answers The F factor is present in strains that are
able to transfer genes by conjugation
Have the ability to donate ability
Can be lost and regained easily
Strains carrying F are donors and designated F+
Strains lacking F are recipients and designated F-
F is a conjugative plasmid which encodes the machinery for conjugation
Currently the only T4SS known that can dynamically extend and retract
What is the minimised type IV secretion system? correct answers This is encoded in small
plasmids (<20kb) or genomic islands following prototypical VirB genetic organisation
It is capable of mobilising ssDNA (small plasmids) or protein toxins
Shorter pilus that was thought to be made of cyclic pilins (not true)
Structurally organised in four main sub-assemblies: conjugative pilus, outer-membrane core
complex (OMCC), IM complex and energy centre (VirB4, VirB11 and VirD4 ATPases)
This system is leveraged for bacterial killing
What is the composition of the minimised T4SS? correct answers Has ~12 subunits to be built
VirB1-B11 + VirD4
