Deck 3

Question 1

Osmiotrophs

Answer 1

Organisms that secrete enzymes into the surrounding substrate and absorb digested nutrients (fungi)

Question 2

Conidia

Answer 2

vegetative spores formed by fungi

Question 3

Asexual life cycle of molds

Answer 3

Dispersal -> conidia -> (swelling and apical growth) -> Germling -> (elongation and branching) -> hyphae -> mycelium -> condidophore (conidia-carrier - releases spores)

Question 4

fungal mycobiota of the human skin

Answer 4

Mostly Malassezia species (11 identified)

Question 5

fungal mycobiota of the human lung

Answer 5

Pneumocystis jiroveci

Question 6

Structure of fungal cell wall

Answer 6

from inner-most to outer -most:

plasma membrane
Chitin layer
B-1,3 glucan
B-1,6 glucan
outermost layer differs between species, but often contains mannan (mannoproteins in Candida)

90% of the cell wall is carbohydrate

Question 7

Clec7A

Answer 7

Dectin-1, recognizes B1,3 glucan

Question 8

During what process are fungal antigens most likely to be exposed?

Answer 8

During the budding of the yeast, underlying proteins and B-glucans are exposed that can be targeted antigenically. Otherwise, they are hidden beneath the carbohydrate cell wall.

Question 9

How does the immune system differentiate between shed (soluble) and particulate B-glucan from fungi?

Answer 9

Dectin-1 requires cross-linking for activation, as it is blocked by CD45 phosphatase.

Question 10

Mutations in which genes lead to redisposition to candidiasis?

Answer 10

Dectin-1
CARD9
Phagocyte oxidase
IL-23R
STAT-3
STAT-1
IL-17
IL-17RA
or, autoantibodies to IL-17, IL-22

Question 11

What are the two layers of sensing of C albicans on the skin?

Answer 11

In the epidermis, yeast forms of C albicans are sensed by Langerhan cells, which use Dectin-1 to initiate Skin Th17 responses, while dermal (deeper) hyphal infections activate CD103+ DCs that use TLR2 to initiate Th1 responses.

Question 12

Heterokaryon Incompatibility

Answer 12

When fungal hyphae fuse, they can share their genetic material. If certain loci differ between the two ‘parent’ strains, they must be compatible hets. If they are uncompatably different, the cell undergoes regulated cell death.

Question 13

What is the function of BIR1 in Aspergillus and what seems to activate its expression?

Answer 13

BIR1 is a negative regulator of programmed cel death, ie., its expression leads to increased resistance to cell death. It seems to be activated in the context of oxidative bursts conferred by neutrophils.

Blocking of BIR1 leads to increased fungal clearance.

Question 14

Fungal antigen that elicits the strongest immune response

Answer 14

B-1,3 glucan (is even stronger when simultaneously detected with mannan)

Question 15

Non-lytic expulsion

Answer 15

An actin-dependent
mechanism used by
microorganisms to escape from
within a macrophage. Both the
macrophage and the
microorganism are viable after
expulsion takes place.
Non-lytic expulsion is also
known as vomocytosis.

Question 16

What is unique about the synthesis of B1,3 glucans and chitin in the fungal cell wall?

Answer 16

Polysaccharides such as chitin and glucan are synthesized at the plasma membrane (PM) by transmembrane enzymatic complexes that are targeted to the PM in an
inactive form via secretory vesicles and then activated after insertion into the PM (see below). This is in contrast to mannans and other glycoconjugates that are
synthesized in the endoplasmic reticulum and Golgi, where they may be conjugated to cell wall proteins, and then brought to the cell wall by the classical secretory
route via secretory vesicles

Question 17

What is the substrate used by synthases to insert nascent polysaccharides into the cell wall of fungi?

Answer 17

UDP sugars

Question 18

What is the next step for a nascent polysaccharide that is inserted into the fungal cell wall?

Answer 18

In the cell wall, polysaccha-
rides can then hydrogen-bond together or be cross-
linked or branched by enzymes that reside in the cell wall

Question 19

What is the substrate for chitin synthesis in fungi cell wall?

Answer 19

UDP-N-acetylglucosamin

Question 20

What is the makeup of chitin in fungal cel wall?

Answer 20

Chitin is composed of linear chains of β-(1,4)
N-acetylglucosamine and represents the most ancestral
structural polysaccharide in the fungal cell wall

Question 21

target of the echinocandin family of antifungal drugs

Answer 21

The Fks/Gsc subunits of the PM-bound glucan synthase in fungi that makes B1,3 glucan chains for insertion into the cell wall

Question 22

PfAP2-G

Answer 22

“Master switch” for sexual differentiation in Plasmodium falciparum/ (“Pf” stands for the organism, AP2-G is the transcription factor)

Question 23

Malaria parasite genus/species

Answer 23

Plasmodium falciparum

Question 24

How is sexual differentiation controlled in P. falciparum at an epigenetic level?

Answer 24

heterochromatin maintenance at the ap2-g locus keeps P falciparum at asexual replication. When heterochromatin maintenance is impaired, low level ap2-g expression can induce its own promotion through a positive feedback loop, inducing sexual differentiation.

Question 25

Which phospholipid precursors suppress sexual commitment in P. falciparum?

Answer 25

lysophosphatidylcholine (lysoPC) and choline, both precursors to phosphocholine headgroup.

Question 26

SAM / SAH

Answer 26

S-adenosylmethionine (SAM) and S-adenosyl homocysteine (SAH) - SAM is the major source of methyl groups for transferring via methyltransferases, and is used by both PMT for P-cho synthesis and histone methyltransferases for heterochromatin maintenance.

Question 27

Which phospholipid accounts for the vast majority of phospholipid increase during a P falciparum infection of RBC?

Answer 27

Phosphatidylcholine (PtdCho)

Question 28

Which are the two pathways that P falciparum can de novo synthesize phosphatidylcholine?

Answer 28

Always derived from phosphocholine, which can be either generated from serine via phospho-ethanolamine or scavenged from extracellular choline and LysoPC.

Question 29

phosphoethanolamine methyltransferase (PMT)

Answer 29

generates phosphocholine by transferring three consecutive methyl-groups from the methyl donor S-adenosylmethionine (SAM) onto P-etn

Question 30

How is PMT regulated in P falciparum?

Answer 30

High levels of phosphocholine (PMT's product) inhibit PMT activity/levels.

Question 31

SAMS

Answer 31

SAM synthase, malaria parasite enzym that is the sole producer of SAM from methionine.

Question 32

3-DZA (3-deaza-adenosine)

Answer 32

potent inhibitor of SAH hydrolase, which converts SAH into adenine and homocysteine (treatment with 3-DZA will lead to increased levels of SAH)

Question 33

Which histone modification is the most potent regulator of gene expression in P falciparum?

Answer 33

H3K9me3 (silencing)

Question 34

How does low SAM levels in P falciparum lead to sexual differentiation commitment?

Answer 34

SAM is the only source for methyltransferase enzymes that are needed for heterochromtin maintenance. In the absence of SAM substrate, heterochromatin cannot remain faithfully methylated, and low level gene expression results. This includes the typically silenced ap2-g locus, which promotes its own expression and leads to sexual commitment in P falciparum.

Question 35

Which two survival processes do sexual and asexual reproduction in P falciparum contribute to?

Answer 35

asexual reproduction is required to maintain sufficient levels of parasite within the host, whereas sexual production of gametocytes is required for the transmission to mosquito hosts.

Question 36

schizogony

Answer 36

replicative process of parasites wherein continuous rounds of nuclear repli- cation produce a single multi-nucleated cell that gives rise to 16–30 new merozoite progeny through a single round of cell division near the end of the lytic cycle

Question 37

What recognizes H3K9me3 histone modifications?

Answer 37

heterochromatin protein 1 (HP1)

Question 38

How does LysoPC alter sexual commitment in P falciparum?

Answer 38

LysoPC suppresses sexual commitent. LysoPC acts as a substrate for phosphatidylcholine synthesis, freeing up SAM (used in the alternative phosphatidylcholine pathway) as a substrate for histone methyltransferases that can maintain heterochromatin.

Question 39

Rodent malaria genus

Answer 39

Plasmodium berghei

Question 40

Why is rodent Plasmodium resistant to the sexual commitment suppression effects of LysoPC?

Answer 40

Rodent Plasmodium species have lost PMT gene, meaning that they are unable to utilize LysoPC as a substrate for phosphatidylcholine. To compensate, these parasite have an expansion of transporters that allow for extracellular phosphatidylcholine import.

Question 41

How do high SAH levels suppress sexual committment in P falciparum?

Answer 41

High levels of SAH generally inhibit meyhtltransferase activity, which leads to loss of heterochromatin maintenance in the genome.

Question 42

What is the medicine and biological way to define parasites?

Answer 42

Medicine: Pathogen that is not a bacterium, virus, or fungus. Biological: An organism living in association with another (usually larger) organism (the host) benefitting at the host's expense.

Question 43

What are the four/five types of motility in protozoa?

Answer 43

``` Flagellated amoeboid gliding ciliated non-motile ```

Question 44

Definitive Host for parasite

Answer 44

Definitive host is the host wherein the parasite undergoes sexual replication. This is, for example, mosquitos for malaria.

Question 45

Intermediate Host for parasite

Answer 45

Intermediate hosts are hosts wherein the parasite does not undergo sexual replication, but it is required for other life stages that are crucial for the life cycle of the parasite.

Question 46

Accidental Host for parasite

Answer 46

Accidental hosts are hosts wherein no integral portions of a parasite's lifecycle occur; the parasite will likely die out within that host. Brain-eating amoeba in humans is one example

Question 47

What are different ways in which parasites can cause disease?

Answer 47

Immune evasion (malaria trying to avoid the spleen leads to blood clots, compared to toxoplasma, which activate teh immune response purposefully) Tranmisssion (diarrheal parasites need the disease for transmission) Immune mediated (think COVID for example)

Question 48

Metamonads

Answer 48

Trichomas and Giardia.

Question 49

Trichonomas vaginalis

Answer 49

Single stage, human-specific lack mitochondria, have hydrogenosome instead (uses pH for energy) Evades immune response by antibody proteases.

Question 50

Giardia lamblia

Answer 50

single mammalian host (beaver), produces very stable cysts that pass with the feces. Antigenetic variation of surface proteins. Adheres to intestinal lining using flagella to create suction.

Question 51

Kinetoplastids

Answer 51

Trypanosoma and Leishmania 2nd most medically relevant large family, huge range, single mitochondrial organelle called kinetoplast

Question 52

Kinetoplast

Answer 52

Single mitochondrion in kinetoplasts that is located at the base of the flagellum. kDNA is very large catenated disk of dozens of maxi-circles. During replication, it has to be untangled, replicated, and re-tangled. High RNA editing (each minicircle contribute to the editing of transcripts that comes from the maxi-circles)

Question 53

Polycistronic transcription

Answer 53

Whole chromosome is transcribed at once and transcript is cut and polyadenylated individually. Hardly any epigenetic regulation on the DNA level.

Question 54

Why is 'sleeping sickness' almost always lethal?

Answer 54

African trypanosomes have extremely high antigenic variation (VSG protein), and often sweep their antigens backwards and degrade bound antibodies. Thus, the adaptive response can never 'catch up' Only one VSG gene is active at any time

Question 55

Leishmania target cell in humans

Answer 55

Live inside macrophage lysosomes (intracellular pathogen) Transmitted by sandfly.

Question 56

Apicomplexa parasites

Answer 56

Plasmodium, Toxoplasma, Cryptosporidium Most important group medically. Every species are parasitic, all obligate intracellular at one point.

Question 57

What is the unique biology of the Apicoplast?

Answer 57

It is derived from two endosymbiotic events and thus has four membranes surrounding it - first was a cyanobacteria engulfed by an algae, followed by the engulfment of both by an apicomplex parasite This parasite is therefore susceptible to some antibacterial antibiotics due to this organelle.

Question 58

What is unique about the intracellular invasion of apicomplexa parasites?

Answer 58

They will invade a cell membrane and invaginate the plasma membrane, while using a 'molecular sieve' to remove any transmembrane proteins - thus, the resulting vacuole is 'naked' and cannot interact with any intracellular proteins (prevention of lysosomic fusion)

Question 59

What is one reason that toxoplasma has such a broad host range?

Answer 59

Toxoplasma inserts its own receptor for invasion into the host cell - therefore, it does not require a matching host cell surface receptor

Question 60

Schizogony

Answer 60

Type of replication in malaria parasites. Nuclei continue to divide along side essential organelles without division of the plasma membrane. After there are ~30 nuclei, all separate into individual cells (somehow)

Question 61

Dormant hypnozoites

Answer 61

Certain malaria parasites (P. vivax and P. ovale) have dormant liver stages called hypnozoites that can reactivate and cause relapse up to 10 years later after initial infection

Question 62

How long is the RBC lytic cycle for malaria parasites?

Answer 62

48 hours. This causes the periodic fever spikes - synchronous bursts causes bursts of cytokines in the blood. The fever response controls the synchronicity.

Question 63

What is the quality control of RBCs conferred by the spleen?

Answer 63

The spleen filters RBCs and ensures that they are sufficiently pliable in order to squeeze through the capillaries. RBCs with tons of parasites obviously fail this test, so malaria must find a way to avoid the spleen.

Question 64

How does malaria avoid being cleared by the spleen?

Answer 64

Malaria makes surface proteins that are trafficked to the plasma membrane of the iRBC that interact with endothelial cells - cytoadhesion - that prevents their circulation. This is where most of the pathogenesis of malaria arises from, apart from anemia from hemolysis.

Question 65

Why does toxoplasma want to activate the immune system?

Answer 65

Toxoplasma has a highly *invariable* surface antigens - infects recruited DCs and changes DCs to be more motile to disseminate to other tissues. It 'wants' to be controlled by the immune system - forms cysts when targeted by the immune system.

Question 66

Tachyzoite

Answer 66

Toxoplasma form - fast replication and host cell lysis (1 day), resulting in tissue destruction Disseminates by infecting monocytes Invariant SAG1 surface coat SAG1 is highly immunogenic

Question 67

Bradyzoite

Answer 67

Toxoplasma form Slow replication, long term stability (months) Forms protective cyst wall No SAG1 expression

Question 68

What triggers the tachyzoite to cradyzoite conversion in toxoplasma?

Answer 68

Nitric oxide, TNFa, IFNg

Question 69

What determines where in the world that we can find malaria

Answer 69

1. Definitive host range (mosquitos) 2. High enough temperature for replication to be fast enough in mosquitos before they die 3. Infected people

Question 70

Tuft cells

Answer 70

A very rare chemo-sensing epithelial cell type that is spread throughout the gastrointestinal and respiratory tracts. Tuft cells secrete the alarmin IL-25 in response to parasitic infections and perhaps other stimuli and are thought to be important sentinels for and innate initiators of the type 2 response.

Question 71

Goblet cells

Answer 71

A specialized, mucus-secreting epithelial cell found throughout the gastrointestinal and respiratory tracts and across mucosal surfaces. Goblet cells and their secreted mucins are critical for protecting mucosal surfaces, maintaining barrier integrity and removing large extracellular irritants and debris.

Question 72

Alarmins

Answer 72

considered to be some of the earliest of the type 2 cytokines to be secreted following tissue damage, and they have the capacity to both initiate and propagate a fulminant type 2 immune response Include IL-25, IL-33, and thymic stromal lymphopoietin (TSLP)

Question 73

What are the specific ligands from microbial communities?

Answer 73

``` TLR and NLR ligands Adenosine SCFAs PSA SlpA metabolites ```

Question 74

ILC2 phenotype in the lung

Answer 74

Lin-CD25+CD127+IL-33R+

Question 75

What do all kinetoplastids have in common in their transmission?

Answer 75

All kinetoplastids are transmitted by an insect host at some point in their lifecycle.

Question 76

What is unique about trypanosome genetics (besides kinetoplast)?

Answer 76

Genome is polycistronic - has one promoter that encodes the entire genome, which is then spliced and polyadenylated by other means.

Question 77

How do malaria parasites sense that they are in a host fly?

Answer 77

drop in temperature, xanthurenic acid (in the gut of flies), change in pH.

Question 78

VSG in trypanosomes

Answer 78

Variant Surface glycoprotein that covers the entire outer surface of trypanosomes. Highly variable and used to thwart the immune system by expressing different types.

Question 79

How is antigenic diversity maintained in a chronic trypanosome infection?

Answer 79

There are a large reservior of silent. VSG genes. Many are encoded on small, circular minichromosomes (~100) and many more are encoded sub-telemeromically (~1000). These genes can be converted in a similar manner to V(D)J recombination where different parts of different VSG genes are spliced together, or a new VSG gene is switched out altogether.

Question 80

What is the only point of endo- and exocytosis in trypanosomes?

Answer 80

The flagellar pocket (targeted by innate immune system ApoL1)

Question 81

SRA

Answer 81

Serum Resistance Associated gene evolved by some species of trypanosomes to prevent ApoL1 from lysing their lysosome, thus being able to infect humans.

Question 82

Eflornithine

Answer 82

failed cancer drug that kills trypanosomes efficiently. PRoduction was ceased in 1995 by Aventis. In 2001, they resumed production because it was discovered that it was also a hair removal treatment ($$$)

Question 83

Artemisinin

Answer 83

Discovered by Tu Youyou (Nobel Prize). Malaria treatment drug that targets free iron (digested by malaria from hemoglobin) Iron bound by hemoglobin in the blood is not affected. Has a very short halflife (90 minutes) that some parasites have evolved resistance to through alteration of their cell cycle length.

Question 84

Digestive vacuole in malaria parasites

Answer 84

Vacuole wherein hemoglobin is digested, freeing up amino acids for the parasite. The iron that is released is crystallized into hemozoin, which is targeted by quinine and other treatment drugs and stored in the digestive vacuole (also makes them magnetic).

Question 85

Hemozoin

Answer 85

crystallized iron from digested hemoglobin in malaria infections (stored in digestive vacuole of malaria)

Question 86

Why can only immature malaria iRBCs be identified in the circulation

Answer 86

More mature iRBCs are swelled and distorted and thus need to avoid clearance by the spleen, thus they cytoadhere to the endothelium.

Question 87

PfEMP1

Answer 87

Surface protein receptor that is expressed on the PM of iRBCs and binds to endothelial receptors in order to cytoadhere. Malaria is able to undergo significant antigenic variation of this protein to avoid immune detection.

Question 88

var genes

Answer 88

genes encoding different forms of PfEMP1 proteins in malaria parasites. Under epigenetic control (so, no recombination).

Question 89

uORF

Answer 89

upstream reading frame of a particular var gene in malaria that encodes for a PfEMP1 protein that targets the placenta (var2csa). uORF disallows transcription of var2csa unless in a pregnant woman. Also, var2csa serves as a 'node' to switch to between variations.

Question 90

How does adding additional choline lead to changes in var gene expression in malaria parasites?

Answer 90

Choline is upstream of the CDP pathway, which uses the CDP pathway for lipid synthesis without the need for SAM for methyl groups. This increases the SAM pool that is available for the methylation used by HMTs to trigger histone modification and gene expression.