BIOL0510: Protists and Helminths (Eukaryotic Microbiology)

List common infections caused by protists

• malaria: spread via misquito bites

• trichomonas: sexually transmitted protozoan infection (STI)

• giardia: by drinking contaminated water; intestinal cramps and diarrhea

• cryptospordium: #1 cause of recreational water disease outbreaks (ex. in lakes and ponds)

• taxoplasma: forms cysts in muscles and brain; spread by cats

What are the four kingdoms of eukaryotes? Make sure to define any subcategories.

1. fungus

2. protists

   • protophyta: protists that are more plant-like (ex. have pigments seen in plants)

   • protozoa: protists that are more animal-like (ex. have motility structures)

3. animals

   • helminths

4. plants

What does the term “protist” mean?

describes any microbial eukaryote that is not a plant, animal or fungus (60,000-200,000 species)

Draw a more detailed phylogenetic tree corresponding to the branch of eukarya. Include plant, fungi, and animal branches

List the five protist clades

1. archaeplastida

2. SAR clade

3. excavates

4. amoebozoa

5. opisthokonta

Describe the archaeplastida clade

• describes the entire plant kingdom and algae

• all are photosynthetic

• the lineage resulted from primary endosymbiosis (eukaryotic cell engulfed a cyanobacterium, where the two eventually evolved to depend on each other) of chloroplasts

What evidence supports the endosymbiotic theory?

• similar size as chloroplasts

• MIN 15

Describe an example of an organism from the archaeaplastida clade

characteristics:

examples:

Describe the characeristics of Stramenophiles (from the SARS clade)

characteristics:

• short, hair-like extensions

• chemoorganotrophic and phototrophic members

Describe diatoms: stramenophiles

• in fresh water and marine habitats

• cell walls made of silica

Describe oomycetes: stramenophiles

• water molds - filamentous growth

• cell walls are made of cellulose

Describe golden algae: stramenopiles

• most are unicellular

• motile via flagella and some are colonial

• chloroplast pigments dominated by fucoxanthin

Describe brown algae: stramenophile

min 20

Potato famine example

min 20

Describe the characteristics of alveolata (SARS clade)

characteristics:

• presence of alveoli (sacs underneath the cytoplasmic membrane)

ex.

• cilliates

  • possess cilia at some stage in life

• dinoflagellates

  • some are free-living

• apicomplexans (causes malaria)

Describe Rhizaria (SARS clade)

characteristics:

• have threadlike pseudopodia that they use to move and feed

ex. chlorarachniophyta, foraminifera, radiolarians

What is the difference between primary and secondary endosymbiosis? Use an example of each to explain

• primary:

  • ex.

• secondary:

  • ex. chlorarachniophyta: chloroplasts have 4 membranes (instead of 2) derived from engulfed eukaryotic algae

Describe the clade: Excavates

characteristics: an asymmetrical appearance with a feeding groove

Discuss 3 subgroups of excavates

1. diplomonads (cause waterborne illness)

   • have 2 equal-sized nuclei

   • ex. giardia intestinalis

2. parabasalids

   • lack mitochondria but have hydrogenosomes for anaerobic metabolism

   • most genes lack introns

   • ex. trichomonas (most common STI)

3. kinetoplastids (causes african sleeping sickness)

   • has a mass of DNA present in their single large mitochondrion

   • ex. LIST THE 3

break up this slide!!!!!

List the characteristics of amoebozoa

• terrestrial and aquatic

• use pseudopodia for movement and feeding

• ex.

  • slime molds

  • gymnamoebas

  • entamoebas

List and describe the subgroups of amoebozoa

1. gymnamoebas

2. entamoebas

3. slime molds

Describe opisthokonta clade

includes animals, fungi, and. the protists Choanoflagellida and Nucleariidae

NEED TO KNOW OF THE STUFF IN SLIDES 1-22

• name and list characteristics of 3 nonpathogenic protists

Describe parasitism

a type of symbiosis: organisms that obtain food and shelter by living on or within another organism

• physiologically and metabolically dependent on the host

kinds of symbiosis: commensalism, mutualism, parasitism

What is a parasite in medical terms?

a eukaryotic pathogenic organism belonging to protozoa and helminths

List and define the different types of parasitic hosts?

• host:

• definitive host: the organism that the parasite lives in during its adult and sexual stage

• intermediate host

  • vector

• reservoir host

• paratenic host

Explain the two ways parasites are transmitted?

• direct: 1 host

  • ex. cryptosporidiosis in contaminated water is ingested by a person who then becomes the definitive host

• indirect: intermediate host

  • the duck is the definitive host because it produces an egg which transmits the pathogen to the snail and, eventually, the human

Define the types of parasites

• obligate: only live in host

• facultative: live in host or free form

• endoparasites: live inside host body

• ectoparasites: live on host body surface

• epiparasites: live in or on another parasite

What is the difference between horizontal and vertical parasite transmission?

horizontal: from infected host to neighbor

vertical: mother to offspring (during fetal development - 2 weeks post-birth)

• rare with parasites

both apply to bacteria as well

What is spillover and spillback transmission?

spillover:

spillback:

Know 3 examples of maternal-fetal infections

List the 3 types of protist (protozoan) infections

1. trypanosomes

   • leishmania

2. trichomonas

3. toxoplasma

Describe Leishmaniasis (cause, cases, symptoms (3), hosts, and target)

cause: several Leishmania genus species

cases: 12 million, 1 million/year

symtoms:

• cutaneous lesions that eventually create ulcers

• mucocutaneous ulcers develop on the oral or nasal mucosa

• visceral: found throughout the body

hosts: multiple (ex. humans, dogs, monkeys)

target: macrophages

Describe Trichomoniasis

what: trichomonas vaginalis (most common STI)

cases: 2 million/year

host: more common in women

symptoms: 70% of patients are asymptomatic

Describe Toxoplasmosis

cause: Toxoplasma gondii

cases: worldwide distribution (1/3 of the population has it)

symptoms: mostly asymptomatic

• symptomatic people develop cysts in muscles and sometimes other tissues (ex. brain)

spreads: via domestic cats

rare complications:

• pregnancy: premature birth, stillbirth, miscarriage, blindness, fetal brain damage

• immunosuppressed people at risk of encephalitis, myocarditis, and pneumonitis

Describe the lifecycle of toxoplasma

1. cysts ingested by cat (definitive host)

2. unsporulated toxoplasma oocytes are released in feces

3. oocytes sporulate and spread to food, water, or soil, eventually being ingested by intermediate hosts (mice)

4. cysts form in intermediate hosts’ tissues

5. ingesting cysts in infected meat (raw or undercooked) passes toxoplasma to humans

6. tachyzoites can then be transmitted through placentas to fetuses

List examples of helminths and their death rates

Describe helminths

• in the animal kingdom

• invertebrates

• macroscopic and multicellular

• considered worms

• either free-living or parasitic in nature

• 1/3 of world population is infected with a helminth currently

List the elements of helminth anatomy

• they are cephalopods (have a head)

• bodies covered in tough cuticle

How do worms acquire nutrients in host?

through absorption or ingestion of host body fluids

HIGHLY DEVELOPED… FINISH

Why are we worried more about oviparous infections than viviparous worm infections?

oviparous

List elements of helminths that aid in their defense mechanisms

• tough cuticle protects from enzymes

• large size

• elaborate attachment to host

• might have multiple hosts and shift to the more favorable environment at a given time

• hide out in immunologically protected areas (brain, spinal cord)

• can sometimes suppress host immune system

• shed surface antigen once host antibodies attach to surface

Which types of worms cause human infections?

platyhelminthes (flatworms) and nematoda roundworms

Describe flatworms (platyhelminthes)

physical: soft body, ribbon-shaped, flat, mucoid, eye spot and brain, incomplete digestive system (no anus)

• undulating form of locomotion

What are the two subcategories of flatworms we discussed?

1. trematodes (flukes)

2. cestodes (tapeworms)

Describe an example of a trematode: Schistosomiasis (snail fever)

definitive host: human

intermediate host: snail

area: subsaharan Africa

infection: egg in fecal material gets to drinking water; uses snail as intermediate host to mature; passes to fish; human eating the fish acquires infection

Describe cestodes

min 4:10

List the characteristics of nematodes (roundworms) and provide examples

unsegmented, cylindrical fusiform body that is bilaterally symmetrical

ex.

• whipworms

• FINISH

Describe the nematode case study: lymphatic filariasis

min 73

Describe the nematode case study: Guinea worm

nematode: Dracunculus medinensis

prevalence: 14 human cases in 2024

contraction: ingesting contaminated water

symptoms: itch that only feels better when skin is subjected to water

• problem: when affected body parts are submerged in water, the female worm releases larvae, which are ingested by copepods (fish that are eaten again by humans, thus spreading the infection)

Which populations are at risk for helminth infections?

FINISH

How are helminth infections diagnosed?

• asking about travel history and food intake

• elevated eosinophil numbers (a type of WBC)

• morphological

• FINISH

What treatment exists for helminth infections?

1. prevention: increasing sanitation

2. early chemotherapy

   • was toxic

     • heavy metals (arsenic)

     • quinine (toxic metabolites accumulate in parasite cells)

     • f

     • p

What is premunition? Why might it be good to have it for a helminth infection?

resistance to a disease due to the persistence of viable organisms at low concentrations within the body of the host

• a small amount of helminths in the body can provide immunity

How do eosinophils and IgE work together to expel worm infections?

Describe the hygiene hypothesis

an ultra-hygenic environment fails to educate our immune system and increases the risk of developing allergies, asthma, and autoimmunity