12 Eukaryotic Members of the Microbial World

Eukaryotic

All members of the domain Eukarya are [__] (adj.)

• contains membrane-bound organelles

  • eg. nucleus, mitochondria, endoplasmic reticulum (ER), etc.

• more complex

• single cell or multicellular organisms

  • eg. algae, fungi, protozoa, helminths

• can undergo both asexual and sexual reproduction

Fungi

Eukaryote that can be single-celled (yeast), or multicellular (molds, mushroom)

• cell wall consists of chitin → same sugar found in exoskeletons of insects and crustaceans

• major decomposers

  • excretes enzymes to degrade larger molecules

• exist in many places

  • mostly terrestial (air, soil, surfaes)

• some pathogenic

  • large amount cause disease in plants

  • only a few cause disease in humans

yeasts

Single-celled fungi

• spherical oval or cylindrical

• reproduces through binary fission or budding

  • budding: asexual reproduction wherein the nucleus divides by mitosis and migrates into a smaller cell known as a bud

molds

Filamentous, multicellular fungi containing hypa (plural: hyphae): microscopic filament of mold that branches and twists to form mycelium

• single celled reproductive spore (sporangium) germinates and develops in hyphae

dimorphic fungi

Fungi that can grow as yeast (single-celled) or mold (multi-cellular) depending on the environment

Many pathogenic fungi are [__]!

When they are out in the environment, they are in mold form

When the are causing an infection, they are in yeast form

mycoses

Immunocompromised individuals are more susceptible to fungal disease

Fungi can cause disease in 3 ways:

• allergic reaction, from fungal spore inhalation

• fungal toxin reaction

  • may have hallucinogenic properties

  • certain species produces aflatoxin, a toxin implicated in cancer

• [__]: fungi that grows on or in the body. fungal infection

  • eg. Candida albicans: yeast part of normal flora

    • → overgrowth due to change in pH or antibiotic therapy can lead to:

    • dermitis: creates ulceration of the skin

    • thrush infections (vaginal, oral) → first sign of being immunocompromised

lactobacilli

Women of Reproductive age typically have this bacteria in their vaginal canal that breaks down sugar and produces a lot of acid → maintains acidity that keeps Candida albicans yeast in check

When they take antibiotics, [__] die » Candida albicans can overgrow in the higher pH

hallucinogen toxin

The Economic Importance of Fungi lies in their ability to

• destroy human food supply → cause starvation

  • spoilage of food and crops

  • notably, the Irish Potato Famine from 1845-1847

    • water mold decimated crops

    • est. 1.5 million people died → 25% of Ireland population

• produce toxins

  • Aflatoxins produced by Aspergillus species, which is carcinogenic

    • found in grains and peanuts

  • [__] produced by rye mold (Claviceps purpurea) → produces ergot toxin → causes ergotism: disease of severe convulsions, hallucinations, and blood constriction

    • this is responsible for Salem Witch Trials

• produce commercialized products

  • eg. beer, wine, bread, cheese, antimicrobial agents

• aid in genetic and biochemical studies

  • yeast is genetically engineered to make human products (eg. human insulin gene and hepatitis B vaccine)

  • much better than bacteria as they secrete products outside automatically; do not have to be lysed like bacteria

Algae

A photosynthetic (contains chlorophyll) Eukaryote that can be unicellular (microscopic) or multicellular (macroscopic)

• found in both fresh and salt water, alongside soil

• rigid cell wall is made out of cellulose

has various types:

[__] doesn’t cause disease directly

• has toxins which are poisonous to humans → cause disease

• seasonal algal blooms: a rapid increase in population of microscopic algae in a body of water

  • eg. “Red tide” caused by dinoflagellates

    • » when shellfish eat the dinoflagellates, they produce neurotoxins

    • » humans ingesting shellfish suffer paralytic shellfish poisoning → die primarily from respiratory failure

Protozoa

Microscopic, single-celled Eukaryote that is found in water, on land, and in parasites. [__] → “animal-like”

• complex; much larger than a prokaryote

  • has a complex life cycle

• lacks a rigid cell wall

• mostly motile through a cilia, flagella, or pseudopodia (temporary arm projection)

Many cause disease

• Giardia lamblia → causes giardiasis

• Trichomonas → STDs

• Plasmodium → malaria

• Toxoplasma → toxoplasmosis

Giarda lamblia

The protozoa responsible for causing giardiasis: gastrointestinal infection → very contractive diarrheal illness that is often asymptomatic

• forms cyst that is shed in feces of animals and humans, which contaminates water that could be drunk

• symptoms (if they occur) are foraminating (foamy/gassy) diarrhea → “explosive diarrhea”

• can stay with person for 30 years

Trichomonas

Protozoa responsible for causing STDs

• [__] vaginalis effects seen mostly in females as vaginitis (inflammation/infection of vagina); less outward symptoms in males

• causes irritation, no long-term effects

• identifiable by wet mounts

Plasmodium

An intracellular pathogenic protozoa that occupies red blood cells and causes malaria: disease with flu-like fever symptoms and pain in joints and muscles

• transmitted by mosquitoes

• migrates to the liver and then the RBCs

• no.1 cause of death of pregnant women in the world; (no.1 cause of death in the US is domestic violence)

  • infects ~219 million / year » ~660,000 deaths

• identified by blood smear

Toxoplasma

Protozoa associated with causing toxoplasmosis: disease that affects the brain through hemolytic processes, leading to bleeding and dementia,

mainly associated with cats → shed cysts in their feces in litter box

• when infected, pregnant women are likely to pass disease unto fetus (crosses placenta)

• immunocompromised individuals contract disease through consumption of infected beef

This protozoa and disease can be identified by brain biopsy

helminths

Multicellular, Eukaryotic parasitic worms. Includes:

• free-living and parasitic worms

• roundworm: [__] with cylindrical tapered body. i.e, (nematodes)

• flat worms: [__] with flat body form. further divided into

  • tapeworms (cestodes)

  • flukes (trematodes)

• obtained from water and soil

• common in children all over the world in developing countries

Nematode

Helminth; also known as a round worm.

Invades GI tract and bloodstream

• pinworms » ingested in food

  • symptoms of anal itching come from [__]s depositioning their eggs in perianal skin

• Ascaris » ingested in fish

  • lives in GI tract; robs host of nutrients

  • → children get malnourished

  • → GI tract gets blocked

  • → can enter bloodstream and settle in the lungs

• Trichinella » ingested in animal flesh

  • reproduced in the GI tract

  • larvae travels to and encyst in the muscles

Cestode

Flatworm also known as a tapeworm or flatworms

Contracted from eating undercooked raw meat (beef and pork) or fish

Remains in GI tract and rob host of nutrients or migrate to muscles to encyst

can be 30m long

Trematode

Flatworm also known as a fluke

• found in lakes and ponds

• transmitted through undercooked cray

• sucks fluid from host

arthropods

Multicellular parasite that serves as a vector of transmission

i.e, they can transmit pathogens to humans directly, or indirectly as an organism that the disease can multiply within (like a vector)

Insects

» mosquitos — transmits

→ malaria; symptoms are fevers and chills

→ dengue fever; fever, headache, bleeding and shock

→ West Nile Virus; fever, nausea, convulsions, coma

» fleas → plague (caused by Yesinia pestis);

fever, headache, confusion, enlarged lymph nodes, skin hemorrhage

Ticks

transmit Rocky Mountain Spotted Fever ; fever, hemorrhagic rash, confusion

→ Lyme Disease; fever, rash, joint pain, nervous system impairment

Lice (eg. body lice)

» transmission of typhus; fever, hemorrhagic rash, confusion

and other fevers

Arachnids (eg. mites)

» trigger asthma

» cause intense itching