New Content Micro Final

Define the differences between the kingdoms of protista and animalia. Why aren’t viruses considered a kingdom? What are amoeba?

Protista: unicellular protozoa, includes protists, apicomplexans, study using 18S rRNA gene

Animalia: multicellular metazoa, includes helminths

Amoeba: protists that use pseudopodia for movement and feeding

Viruses aren’t alive, and therefore aren’t considered a separate kingdom. They are considered obligate intracellular parasites.

Describe the differences between a direct lifecycle and an indirect lifecycle and provide an example of each.

Direct: no intermediate host (ex: Giardia)

Indirect: does have intermediate host (ex: Plasmodium and Anopheles mosquito)

Describe the three non-apicoblast protists discussed in this course.

Giardia intestinalis: flagellated anaerobe, equal sized nuclei, tx w/ metronidazole

Entamoeba histolytica: waterborne, liver abscesses

Naegleria fowleri: brain-eating, enters nose, warm water/soil, fatal meningoencephalitis

Describe the nature of apicomplexans and the four described in this course

• Apicomplexans have apicoplasts (nonfunctional chlorophyll remnants) and are protists

Plasmodium: Anopheles, infects RBCs

Toxoplasma gondii: cat feces/undercooked meat, birth defects + brain damage, usually asymptomatic

Leishmania: sandflies, cutaneous/visceral, infects macrophages

Cryptosporidium parvum: Cl- resistant, watery diarrhea, rupture of intestinal epithelial cells, direct lifecycle, low infectious dose, sporozoites, diary calves/piglets

Describe the two types of trypanosomiasis and their vectors

African sleeping sickness: T. brucei in tsetse flies, CNS + spinal fluid

Chagas: American, T. cruzi in kissing bugs, chronic heart + GI symptoms, megacolon/megaesophagus, transovarial + no antigenic variation

• local chancre, mesenchymal cell infection, Romana sign (periorbital edema)

• Mammalian cycle: in humans, extracell trypomastigotes in peripheral blood become intracell amastigotes that divide

Describe lieshmaniasis

Flagellated protozoan, replicates in macrophages, nodules + ulcers

cutaneous/visceral

tx: antimony compounds

Describe the difference between +ssRNA and -ssRNA

ssRNA = single-strand RNA

+ssRNA: ‘ready to read recipe’, acts as mRNA + direct translation by host ribosomes

-ssRNA: ‘needs transcription first’, needs viral RNA polymerase to make mRNA, always packages RdRNAp

dsDNA = double-strand DNA, lower mutation rate, highly stable

Define capsid and naked/enveloped viruses

Protein shell that surrounds genome of a virion

Enveloped: outer phospholipid bilayer + capsid

Naked: no capsid

Define capsomere

Individual proteins patterned around a capsid

Define helical symmetry

Rod-shaped viruses, width determined by size of capsomeres, length determined by length of nucleic acid

Define icosahedral symmetry

spherical, most efficient storage of nucleic acid

Describe the five steps of viral replication

1. attachment/adsorption: requires host cell receptors to match

2. Penetration: T4 lysomizes pore in peptidoglycan, membrane-fusion or R-mediated endocytosis

3. Uncoating/Synthesis: of proheads using ATP

4. Replication

5. Synthesis/Release of progeny (lysis)

Describe the one-step growth curve for viruses

1. latency

2. eclipse: when genome is replicated

3. release (lysis/budding)

4. burst size: #virions/infected cell

Describe the example bacteriophage T4

E. coli, icosahedral head + helical tail, dsDNA, lytic

• 5-hydroxymethylcytosine stops host restriction endonucleases

Define lytic vs temperate

lytic: always lyses host cell

temperate: doesn’t lyse host cell, can be in lysogeny (integrates into host genome + replicates in tandem)

Define lysogenic conversion

the virus imparts new properties onto host bacterium

Describe tropism

the specificity a virus has for a host cell

Describe the four ways parasites are classified

1. motility

2. A/sexual reproduction

3. host location (skin/GI tract/etc)

4. intra/extracellular (viruses vs ticks)

Describe HIV/AIDS

targets CD4+ cells over time, retrovirus

RNA → (reverse transcriptase) DNA→(integrase) into host genome

tx: protease inhibitors (stops cleavage of viral proteins to create immature noninfectious virions [stay undetectable])

1. initial infection

2. acute viremia

3. AIDS progression

4. end-stage AIDS

tx: HAART

no vax? high variability, glycan shielding, CD4 latency, lack of animal model, safety/ethical concerns

Describe the two respiratory viruses in this course

influenza: -ssRNA, antigenic drift/shift, tx w/ neuraminidase, A/B/C, birds

• shift: abrupt change, new hemagglutinin/neuraminidase proteins, reassortment

• drift: small change, mutation

SARS-CoV-2: +ssRNA, uses ACE2r for entry

both: cause cytokine storm, inflammation