Deck 4 Flashcards

Question

What structure is the T3SS related to?

Answer 1

flagellar appartati

Answer 2

Cysteine protease, prevents activation of MAPK and NFkB signalling

Answer 3

Yesrinia T3SS protein, inhibits Rho GTPases (disruption of actin filaments)

Answer 4

Yersinia T3SS protein, a tyrosine phosphatase, which dephosphorylates key actin cytoskeletal proteins and inhibits Ca2+ signaling.

Answer 5

SPI-1: epithelial cell invasion/apoptosis SPI-2, -3, and -4: intramacrophage survival SPI-5: enteropathogenesis

Answer 6

* Primary pathogens are capable of causing overt disease in healthy (immuncompetent) hosts * Opportunistic pathogens primarily cause disease in immunocompromised hosts

Answer 7

virulence factor produced bacteria that force non-phagocytic cells to engulf bacteria

Answer 8

Catalases and superoxide dismutase can reduce and resist oxidative burst

Answer 9

ESX motifs allow for the targeting of mycobacterial proteins to the Esx secretion system. In CpnT, both "Y1" and "Y3" are required for insertion of CpnT into the outer membrane of Mtb.

Answer 10

The ESX-4 system, encoded by the EccC4 gene. ESX-3 and ESX-5 seem to be dispensable. Also important is the ESXF and ESXE complex, which also erequires ESX-4 system.

Answer 11

By using different permeabilization methods: Digitonin permeabilizes only the plasma membrane of host cells, whereas Triton X-100 will permeabilize both the cell membrane and the phagosome.

Answer 12

Tuberculosis Necrotizing Toxin (TNT) gains access to the cytosol of infected macrophages and depletes NAD+, it is a novel NAD+ glycohydrolase. When NAD+ levels drops below a certain threshold, RIPK3 is activated and programmed cell death occurs.

Answer 13

Within the macrophage phagosome, Mtb first makes esxE/esxF, which is exported through ESX-4 into the periplasmic space and inserted into the outer membrane as a pore channel. CpnT is produced and targeted to ESX-4 secretion through the Y1 and Y3 ESX motifs, and is subsequently inserted into the outer membrane by the esxEF pore complex. Finally, TNT is cleaved from the cell surface CpnT by an unknown mechanisms.

Answer 14

Host protein that recognizes luminal glycans that become exposed to the cytosol when a phagosome is extensively damaged. Used to monitor phagosomal disruption in Mtb infection models.

Answer 15

EsxA:EsxB heterodimer secreted by the ESX-1 system is separated into componet parts and EsxA is a membranolytic protein that disrupts the phagosomal membrane.

Answer 16

Phthiocerol dimycoserosate (PDIM) is a lipid virulence factor of Mtb that allows for phagosomal escape by Mtb. PDIM can potentiate EsxA membranolytic activity by either synergizing the pore forming activity of EsxA or by acting on the EsxA/B heterodimer complex separation

Answer 17

Reactive oxygen species, Hypoxia, Starvation (amino acid, nutrient, etc), low pH, Nutritional Immunity (Cu, Zn)

Answer 18

widely distributed in bacteria and participate in diverse pathways, all of which share the requirement for proteolysis of a transmembrane protein

Answer 19

A site-1 protease (S1P) first cleaves the (usually) extracytoplasmic segment of the transmembrane substrate in response to specific inducing signal. This site-1 cleavage is rapidly followed by S2P cleavage within the transmembrane segment of the substrate, thereby liberating the cytosolic fragment of the substrate (often a sigma factor).

Answer 20

Proteolytic signal transduction machinery in Mtb that is essetial for the localization for principal mycolic acids into the outer envelope and thus Mtb is attenuated in its absence.

Answer 21

All reistance in TB is chromosomally acquired, yet we do not understand the mechanisms of mutagenesis in mycobacteria.

Answer 22

CD4 T cell production of GM-CSF and activation of the macrophage transcription factor HIFa, which drives a metabolic shift towards aerobic glycolysis and leads to the production of lipid droplets.

Answer 23

the frequency of IFNg-secreting CD4 T cells correlates more closely with disease severity than with protection from TB disease after M. tuberculosis challenge human trials with the vaccine candidate MVA85A showed that although this vaccine elicits significant numbers of IFNg-secreting CD4 T cells, it does not lead to enhanced protection against infection. Furthermore, while CD4 T cells are clearly important for TB control in humans, inherited mutations in components of the IFNg signaling pathway are not generally associated with susceptibility to M. tuberculosis but rather with enhanced susceptibility to non-tuberculosis mycobacteria. Finally, transfer of IFNg-deficient T cells into mice can control Mtb infection to an extent.

Answer 24

locks the lambda phage into its lysogenic cycle, permitting transcription of λcI only through positive transcriptional regulation

Answer 25

the bacterial response to DNA damage. In uninduced cells, LexA, acts as a repressor of more than 40 genes , including recA and lexA. Upstream from each gene or operon, LexA binds to an operator sequence, called an SOS box. But in induced cells, damage to the DNA creates regions of single-stranded DNA that promotes the conversion of inactive RecA to an active form that can facilitate the otherwise latent capacity of LexA to auto-digest for phage λ, the ‘switch’ from lysogenic growth to lytic growth is regulated by the SOS response.

Answer 26

Superinfection exclusion (Sie) systems are proteins that block the entry of phage DNA into host cells, thereby conferring immunity against specific phages. These proteins are predicted to be membrane anchored or associated with membrane components.

Answer 27

well-characterized virulent phage, has two Sie systems encoded by imm and sp. These systems cause rapid inhibition of DNA injection into cells, preventing subsequent infection by other T-even-like phages

Answer 28

Superinfection exclusion protein that prevents the transfer of phage DNA into the bacterial cytoplasm by changing the conformation of the injection site. Imm has two non-conventional transmembrane domains and is predicted to be localized to the membrane, but Imm alone does not confer complete phage immunity and must be associated with another membrane protein to exert its function and achieve complete exclusion

Answer 29

Superinfection exclusion protein that inhibits the activity of the T4 lysozyme (which is encoded by gp5), thereby presumably preventing the degradation of peptidoglycan and the subsequent entry of phage DNA. The T4 lysozyme is found at the extremity of the tail and creates holes in the host cell wall, facilitating the injection of phage DNA into the cell Sp traps the DNA between the peptidoglycan layer and the outer membrane.

Answer 30

When unmethylated phage DNA enters a cell harbouring a R–M system, it will be either recognized by the restriction enzyme and rapidly degraded or, to a lesser extent, methylated by a bacterial methylase to avoid restriction, therefore leading to the initiation of the phage's lytic cycle. The fate of phage DNA is determined mainly by the processing rates of these two enzymes. As the restriction enzyme is often more active than the methylase, the incoming phage DNA is usually cleaved, although the host DNA is always protected by the methylase activity.

Answer 31

One strategy is the absence of endonuclease recognition sites in their genomes through the accumulation of point mutations some phages have overcome R–M systems through the acquisition of the cognate methylase gene in their genomes T4 phage genome has hydroxymethylcytosine (HMC) instead of the cytosine that is found in the host DNA. This modification allows phage T4 DNA to be impervious to R–M systems that recognize specific sequences containing a cytosine

Answer 32

Abortive infection systems lead to the death of the infected cell. Typically, these Abi systems target a crucial step of phage multiplication such as replication, transcription or translation.

Answer 33

a toxic molecule is produced by the cell and neutralized by the antitoxin product. The expression of these molecules is tightly controlled and varies from system to system but often involves promoter repression or the use of a specific transcriptional terminator. When the balance between the two regulatory halves is altered, the toxin is released and the bacterium dies.

Answer 34

the nuclease responsible for the first step in homology-directed DSB repair in gram-positive bacteria

Answer 35

Myeloperoxidase and Neutrophil Elastase

Deck 4 Flashcards

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