MIC102 S12 - Eukaryotic microbes: Fungi and Protozoa

List the characteristic features of fungi (yeasts, molds)

Characteristic features of fungi

• individual cells about 2-10 micrometers in size

• Non-motile

• Cell wall of polysaccharide (glucans and chitin) and glycoprotein

  • mainly contain ergosterol in their cell membranes

• Produce asexual and sexual spores for dispersal and diversity

• heterotrophs

• lifestyles: decomposer, mutualistic symbiont, commensal parasite

Types of fungi

1) Mold - multicellular fungi

• form multicellular, thread-like hyphae that grow at the tip

  • mass of hyphae = mycelium

  • vegetative hyphae acquire nutrients

  • aerial hyphae are reproductive structures that aid dispersal

• mainly aerobic metabolism

2) Yeast - unicellular fungi

• primarily facultative aerobes

• Most yeasts are budding yeasts that divide asymmetrically

• Some fission yeast divide by binary fission

Example of how fungi can improve or lives or hurt us

Benefits

• Yeast → important for many baked goods

• Penicillin → type of mold and antibiotic

• Mycorrhiza → fungus that has symbiotic relationship with plant roots → stimulate growth

Cons

• Toxic species can look similar to edible species

• Can act as pathogens to us and are difficult to deal with as they are also eukaryotes

Characteristics of Protozoa

• Unicellular eukaryotes → highly diverse

• no cell wall (most) → most have pellicle - layer of closely-packed protein vescicles, assc. with the membrane

• can do sexuala nd asexual reproduction

• vegetative → trophozoite; dormant → tough cyst

Protozoan Diet

• Mainly chemoheterotrophs and are predators of other microbes

• Acquire nutrition through:

  • ingestion

    • take up particles by phagocytosis or sweeping food into mouth pores using cilia

    • digest food inside vacuoles

    • discharge waste

  • absorption

    • take in nutrients through their membrane

  • Pinocytosis

    • “cell drinking”

    • absorption of liquid nutrients

Different Classifications of Protozoa and means of locomotion

1) Amoeboids → Psuedopodia (false feet)

2) Ciliates → cilia (hair-like)

3) Flagellates → flagella (whip-like)

4) Apicomplexa → non-motile, some glide

Benefit and Harm of Protozoa

Benefits

1) Nutrient cycling in aquatic systems → control bacterial population

2) soil health → stimulate bacterial growth through predatiomn

3) bioindicators of qater quality

4) symbiosis → termite gut

5) can indirectly regulate bacterial populations and help humans

Cons

1) Pathogenic

Describe the characteristic symptoms, features, and risk groups of Valley Fever (coccidiomycosis)

Valley Fever

• Caused by Coccidioces spp

• >15,0000new cases/year, 200 deaths/year, 60% asymptomatic

• Symptoms:

  • 30% flu-like symptoms or uncomplicated pneumonia

  • 5% with severe form that can cause chronic pneumonia and lung damage

  • 0.5% dissemination to other organs including brain and spinal cord, leading to skin abscesses, blindness, and death

• Treatment:

  • restt

  • antifungals targeting ergosterol

Risk groups

• weakened immune systems (HIV/AIDS positive or take immunosuppressive drugs)

• altered immune response (pregnancy, diabetes)

• African American or Filipino

• Working is dusty occupations

• Those in CA or AZ

Life Cycle and Transmission Route of Coccidioces

Life Cycle

• Dimorphic

  • 1 - Start out as Hypha in wet soil environments

  • 2 -turn into Arthrocondia in dry conditions → branch off and break off

Transmission

• 3 - Arthrocondia displaced when dirt is displaced → go into air and is inhaled

• 4 - Spore enters the respiratory system

• 5/6 - Arthrocondia turn into spherules (yeast-like form) when it detect human body temp → compartment full of spores

• 7/8 - Spherules break and releases spores that can spread throughout respiratory system and body

Individual behaviors to reduce personal risk and public health measure to reduce incidence of Valley fever

Individual behaviors

• Avoid dust exposure

• Weak mask

• Protect high-risk individuals

• hygiene after outdoor exposure

Public Health measures

• Better ventilation

• Move at-risk population out of certain prisons

• More research and education

• Better healthcare initiatives

Describe the characteristic symptoms, features, and risk groups of Malaria

Malaria

• Mainly caused by Plasmodium

• transmitted by the Anopheles mosquito vector

• 600,000 deaths in 2023, 95% in the WHO African region, mainly chil;dren and immunocompromised adults

Risk Groups/Factors

• Geographic → thrive in warm, humid, tropical (ex: Central/South America, Sub-Saharan Africa, South/Southeast Asia, Oceania)

• Low Socioeconomic regions → limited healthcare, shortage of drugs, rural

• Drug resistance

• Kids, pregnant women, immunocompromised

Symptoms

• Febrile (fever) disease caused by infection of RBC

  • Each 48 hours; result of RBC reupture

    • Short cold stage (chills, shaking)

    • Hot stage with fever (>40C kill mature forms)

• Severity depends on host immunity, host genetics, and Plasmodium species

• Spread depedns on density, feeding preferences, and activity of mosquito vector

• Initial symptoms

  • fever, chills, headache, muscle aches, fatigue, nausea/vomiting

• Severe

  • Seizures, anemia, hypoglycemia, altered mental status, organ failure

Life Cycle and Transmission Route of Plasmodium

Plamodium (parasite) - Anopheles (vector/mosquito) - human (host)

Asexual Reproduction Phase

1) Infected mosquito bites human; inject sporozoites that migrate through bloodstream to liver

2) Sporozites undergo schizogony → form schizonts (multinucleated cell) → schizonts divde and form merozoites (daughter cells)

3) Merozoite released into bloodstream form live and can infect RBCs

4) Merozoite develops into ring stage in RBC

5) Ring stage grows and divides, producing more merozoites

6) Merozoites are released whe RBC ruptures; some develop into make and female gametocytes -

Sexual Reproduction Phase

7) Another mosquito bites infected human and ingest gametocytes

8 ) In mosquito’s digestive tract, gametocytes unite to form zygote that invades gut and grows into sporozoites

9) Resulting sporozoites migrate to salivary glands of mosquito → cycle repeats

Notes

• Steps 1-3

  • liver stage → no RBC destruction

• Steps 4-6 → Asexual Blood Stages

  • These are the steps where symptoms usually show

• Steps 7-9

  • happen in mosquito

Individual behaviors to reduce personal risk and public health measure to reduce incidence of Malaria

Individuals Behaviors

1) Avoid Mosquito Bites → tents, long clothing, repellent, ventilated

2) Chemoprophylaxis (Preventative medication) → antimalarial drugs

3) Awareness of risk

Public Health

1) Vector control → distribute supplies like tents

2) Access to rapid diagnosis or treatment

3) Community education

4) Initiatives to provide for poorer, endemic regions

5) Malaria vaccines

Which stage in Plasmodium replication is the best to target for clinical diagnosis? The specimen should be relatively easy to collect and likely to have a high pathogen load for easy detection.

Options; Select all that apply

A. Sporozoite stage (injected parasite, free in blood)

B. Liver schizont stage (schizont inside liver cells)

C. Ring stage (ring-shaped form inside red blood cells)

D. Gametocyte stage (parasite among red blood cells)

E. Zygote stage (embedded in the mosquito gut)

Correct Answers

• C - early intraerythrocytic stage and abundant in peripheral blood → is most commonly targeted stage

• D - Gametocytes usually circulate and can be present in blood

Why other options not correct

• A - Sporozoite in initial injection are likely in low amounts → hard to detect

• B - Schizont stage → parasite inside liver cells → liver biopsy is invasive

• E - only inside mosquito → difficult to obtain adn not relevant for humans