MIMM 211 Final Review

Not a 100% perfect study guide

2 Types of Parasites

Multicellular (helmiths) and Unicellular (protozoan)

3 Most Common Helmith Infections

Ascariasis (4.2 B at risk), Trichuris (3.2 B at risk), Hookworm (3.2 B at risk)

3 Most Common Protozoan Infections

Malaria, Leishmaniasis, Trypanosomiasis

Treatments for Helmith Infection

Ivermectin and Benziomidazoles to paralyze adults, does not kill eggs

Non-Soil Affiliated Helmiths

Lymphatic Filariasis, Schistosomiasis, and Onchocerciasis

DALY

Disability Adjusted Life Years, amount of healthy years lost due to infection

Plasmodium

Parasite responsible for malaria; forms merozoites in liver that infect red blood cells.Infected RBCs form clots.

Transmitted by mosquito.

Trypanosome Brucei

Causes African Sleeping Sickness, transmitted by Tstete Fly, and affects the central nervous system. Grows in lymph, blood, and spinal fluid.

Endemic to Africa

Trypanosome Cruzi

Causes Chagas Disease, transmitted by Triatomine, and infects muscles. Grows in mastigote cells before bursting out into the blood. Eventually causes heart attack.

Endemic to South America

Leishmania Major and Donovani

Responsible for Cutaneous (Leishmania Major) and Visceral (Leishmania Donovani) leishmaniasis; transmitted by sandflies.

Wuscheria bancroft

Causes lymphatic filariasias (elephantism) by blocking lymph. Mosquito transmitted.

Treatment for Visceral Leishmaniasis

Ambisome, treats in one day

Ascaris Life Cycle

Grows in soil, enters through contaminated food/water, both intestine→lungs→small intestine

Hookworm Life Cycle

Eggs in soil grow into larvae, enter through skin→lungs→small intestine

Wucheria bancroft Life Cycle

Not soil associated, transmitted by mosquitoes. Enters skin→lymph system. Produces microfilaria in to be taken up by mosquitos.

Plasmodium Life Cycle

Mosquito bites, injects sporozoites into skin→blood→liver. At liver, sporozoites turn into merozoites that infect red blood cells. Some merozoites sexually reproduce to make gametocytes.

Trypanosome Brucei Life Cycle

Replicates in spinal fluid/blood and in Tstete fly

Trypanosome Cruzi Life Cycle

Replicates in amastigotes and in Assassin bug, triatomine.

Leishmania Life Cycle

Sandflies inject flagellated promastigotes in blood→macrophages. Eventually, they burst out of macrophages as amastigotes to be taken up by sandflies

Zoosporic Fungi

primitive aquatic fungi, spread via zoospores (asexual), anchored via rhizoid structure, parasite/symbiont/saprotroph

Zygomycetous Fungi

land based, saprotroph, aseptated filamentous fungi, spread via zygospores (sexual) and/or sporangiospores (asexual)

Dikarya

Ascomcyota:

live as septated fungi or yeast, spread via ascospores (sexual) and conidia (asexual)

Basidiomycota:

live as septated filamentous fungi or yeast, spread via basidiospores (mostly sexual)

Basidiospores

Spores germinate to form septated hypae (mating types). Buller’s Drop collects spores as it rolls down gills, surface tension launches spores into convection current.

Ascomycetes spores (ascocarps)

Shotgun (apothecium), rifle (perithecium), and grenade (cleistothecium) to launch spores.

Zygomycetes spores

Spores form at tip of sporangiophore, making a sporangium. Osmotic pressure builds as the fungi grows, finally launches the spores.

Dutch Elm Disease

Mountain Pine Beetle + Blue Stain Fungi (3 species) devastate pine trees. Fungi colonize phloem, feed on sap.

Superficial Fungal Infection

Most common/benign.

Dermatophytes (Tinea)-feed on keratin (ringworm+athlete’s foot).

Candida albicans (yeast)- oral thrush, diaper dermatitis.

Invasive Fungal Infection

Rare and dangerous, normally in immunocompromised patients.

Yeast- systemic, rarely pulmonary (Candida sp.+ Cryptococcus sp.)

Molds- primary pulmonary (aspergillus fumigatis + mucorales)

Dimorphic- primary pulmonary but spreads (Histoplasma + blastomyces)

Candida albicans

yeast, morphologically switch to pseudo- and true hyphae. Can reach other organs through blood vessels.

Cryptococcus sp.

yeast, encapsulated, can infect both immunocompetent and compromised patients. Forms lesion called Cyrptococcosis. Can hijack macrophages to go to brain, causing menigitis.

Aspergillus

Mold, spores land in alveoli and invades lungs.

Invasive- mold grows all over lungs (immunocompromised).

Chronic- mold forms lesion in patients with compromised lung function

Dimorphic Fungi

environmental mycelium form → infecting yeast form. Blastomyces dermatiditis and Valley fever (Coccidioides). Can infect immunocompetent individuals.

Angel of Death (Amanita sp. and Galerina sp.)

contains heat-stable amatoxins, responsible for almost all mushroom poisoning deaths, inhibits RNA poly II

Psilocybin and Psilocin

magic mushrooms, contains agonist to corticol serotonin 5-HT2a receptor, used by Aztecs.

Echinocandins

Fungal cell wall inhibitor, fungicidal in yeast but only fungistatic in mold

Polyenes

Binds to ergesterol, forms ion channels in membrane. Fungicidal in both yeast and mold. High similarity to human cholesterol, so very toxic.

Azoles

Inhibits ergesterol synthesis, fungicidal in mold but fungistatic in yeast.

Effect of Global Warming on Fungi

Increases range, promotes fungi to increase their growing temps.

Mycorrhizal Fungi

symbiotic relationship with plants (80% of plants), most common interactions are arbuscular and ectomycorrhizae. Fungi secrete glomalin (improves soil) and stimulate plant’s immune system.

White Nose Syndrome

P. destructans (ascomcyota) infects bats. Only prevalent in US due to mycovirus. Kills 70%-100% of bats in infected cave.

Fusarium (Wilt and Oxyporium)

Wilt- Drove old banana “Big Mike” to extinction

Oxyporium- Drove Cavendish banana to extinction

Virus

Obligate intracellular parasite with DNA/RNA genome, protein capsid (capsomeres), and possibly phospholipid envelope.

Virion

Extracellular viral particle

Helical Capsid Virus

Spiral/rod shaped, length determined by nucleic acid length, can only package ssRNA

ex. tobacco mosaic virus and ebola

Icosahedral Capsid Virus

Spherical and rigid, packages all genome types, made of identical triangular proteins (most efficient)

ex. most animal viruses, HPV, polio

Complex Viruses

bacteriophages and the pox virus

Enveloped Viruses

Acquire envelope from host during replication/release (budding). Envelope helps with host recognition, provides protection from immune system. Delivers virus via endocytosis or membrane fusion.

Hershey-Chase Experiment

1952, proof DNA is genetic material using bacteriophage T2 and radioactive phosphorus.

Fraenkel-Conrat Experiment

used hybrid viruses to prove that RNA is the genetic material of the tobacco mosaic virus

Giant Virus

Mimivirus, ~1000 genes and 400nm large, able to be co-infected with microvirus

ICTV Classification

Order name: -virales

Family name: -viridae

Genus name: -virus

Class 1 virus

dsDNA

Transcription: uses host RNA polymerase

Replication: uses host machinery

ex. herpesvirus

Class 2 virus

(+) ssDNA

transcription: uses host machinery (RNA poly)

replication: circular genome uses dsDNA intermediate, needs host DNA poly

ex. parvoviruses

Class 3 virus

dsRNA

transcription + translation: uses carried RNA Dependent RNA Polymerase (RdRP)

ex. rotovirus

Class 4 virus

(+)ssRNA

transcription: uses host machinery

translation: encodes for RdRP so (-)ssRNA can be made for template

ex. Hep C

Class 5 virus

(-)ssRNA

transcription and translation: must carry RdRP to make mRNA and to make template

ex. influenza

Class 6 virus

ssRNA w/ Reverse Transcriptase (RT)

must carry RT and integrase to insert into host genome

transcription and translation: uses host machinery for both

ex. HIV

Class 7 virus

DNA w/ RT

uses cellular repair mechanism to convert gapped DNA into fully dsDNA

transcription: dsDNA transcribed into mRNA in nucleus

replication: uses ssRNA intermediate as template for viral reverse transcriptase

ex. pararetrovirus

What classes use viral RdRP?

Classes 3, 4, and 5

Infectious Cycle

Early Phase: attachment/absorption→entry/penetration→ uncoating→ biosynthesis

Late Phase:

biosynthesis→assembly→release

Early vs. Late Protein

Early protein: RdRP

Late protein: capsomere

2 Cycles of Bacteriophage

Lytic Cycle: ends w/ cell death and lysis

Lysogenic Cycle: host remains alive, phage DNA is incorporated

Requirements for Successful Infection

1. enough virus

2. susceptible and permissive cells

3. local antiviral defence absent or overcome

Types of Tropism

Cellular- only replicates in one cell type

Tissue- only replicates in one tissue type

Host- only replicates in one species

3 Types of media for viruses

mature organisms, eggs, and cultured cells

Embyronated Egg

sterile, inexpensive, widely used for growing and isolating viruses, used in vaccines

Mature animals

rats, mice, and guinea pigs

tabacco

Plaque Assay

Culturing viruses in bacteria. Bacteriophages and bacteria are mixed, and the phages lyse the bacteria to make plaques. Plaques can be counted to allow an estimation of phage numbers.

Cell Culturing

Less expensive than mature organisms, sterile and easy to work with. Cells can be primary (derived from tissue) or transformed (cancerous).

Cytopathic Effect

Changes in morphology due to virus infection.

ex. death, swelling, fusion forming syncytia, and changes in inclusion bodies.

Multiplicity of Infection (MOI)

average number of viral particles added per cell, modelled by Poisoon Distribution

Oncogenic Viruses

Viruses may carry oncogene copies, oncogene promoters, or interfere with tumor repressors. All are due to integration with host DNA.

DNA Oncogenic Viruses

Epstein-Barr (dsDNA)

Hep B (dsDNA + RT)

HPV (dsDNA)

RNA Oncogenic Virus

Human Leukemia Viruses (HTLV 1+2)

Some retroviridae

Oncolytic Virus

Virus that infects and lyses cancer cells

mRNA Vaccines

mRNA encoding antigen of choice encased in lipid nanoparticle. Preps the immune system to recognize and eliminate antigen + virus.

Influenza

(-)ssRNA, segmented genome, helical capsid, enveloped w/ glycoproteins (hemagglutinin and neuraminidase)

Very plastic genome = lots of mutations

Pathogenesis of Bacterial Disease

1. Maintain a reservoir

2. Be transported to host

3. Adhere, colonize, and/or invade host

4. Multiply or complete life cycle

5. Evade host defense

6. Leave host to enter new host/reservoir

Direct Contact

droplets, kissing, sex, sneezing, etc.

Indirect Contact

airborne, vehicle borne, vector borne

Virulence Factors

1. adhesins

2. capsules (slimy layer around cell wall)

3. nutrient acquisition systems (siderophosphates - scavenge iron)

4. virulence-associated secretion systems

5. toxins

Virulence Associated Secretion Systems

many different types, but

Type III (T3SS) spans bacterial and host membrane

uses molecular syringe w/ varying proteins

encoded by ~20 genes and present in gram-

Endotoxin

Part of the bacterial cell, such as the LPS of gram - bacteria, released by lysis or reproduction, and heat stable

Exotoxin

Secreted toxin, easily heat inactivated and can be treated with an antitoxin.

ex. botulinum toxin

Exotoxin Categories

1. AB

2. Membrane disrupting

3. Superantigens

4. Categorized by site of action (i.e. neurotoxin)

AB exotoxin

A subunit has enzymatic activity

B subunit mediates cell binding

Intoxication

Disease from pre-formed toxin w/ very fast onset

Enterohemoryhagic E. coli (EHEC)

severe E. coli poisoning, can cause hemolytic uremic syndrome (HUS) in 20% of patients

Due to T3SS injecting Tir and Shiga toxin.

May cause chronic renal and/or neurological syndromes, cannot be treated with antibiotics

What percentage of cells in the body are human?

50%

Holobiome

human genome and microbiome

Methods to Study Human Microbiome

1. 16S rDNA sequencing

2. Deep genomic sequencing

3. mRNA sequencing

4. Metabolomics

16S rDNA

phylogenetic marker found in all bacteria that contains identical and variable sequences unique to certain bacteria

Metagenomics

Sequences all genomic DNA in sample, filters out human sequences, and matches bacterial sequences.

PCA/PCOA plot

Most common microbiota plot graph.

Closer dots are more alike species of bacteria.

Most common skin bacteria

Staphylococci, streptococci, diptheriods

Most common nose bacteria

Staphylococci, streptococci

Most common mouth/oral bacteria

no teeth - aerobes

teeth - mostly anaerobes

Most common urogenital tract bacteria

vagina- lactobacillus

penis- psuedomonadaceae and oxolobactericaea

2 main phyla in Gastrointestinal tract

Bacteroidetes and Firmicutes

Axenic Mice

sterile, lab made mice treated with antibiotics and delivered via C- section