Fungi, Protozoa, and helminths can cause infectious disease in humans

Algae is not infectious but produce toxins

Anthropods can be vectors of transmission

Myco - usually means fungus of some type

Fungi

Features:

• Chemoheterotrophic

• Decompose organic matter

• Plants depend on symbiotic fungi

• Food source and drug source

Compared to bacteria, fungi:

• Grow in acidic environments

• more resistant to osmotic pressure

• can grow in low moisture content

Molds and Fleshy Fungi

• the body (thallus) possess cells in filaments → hyphae (can be septate or coenocytic)

  • Septate - small compartments that’s basically a cell

  • Coenocytic - No compartments; the nuclei basically float around

• Vegetative (submerged) hyphae: nutrient uptake, metabolism, & growth

• Aerial (above the mass of fungus) hyphae - for reproduction → spores

• Mycelium - usually made up of the vegetative hyphae

Life Cycle

• reproduction of fungi

  • Asexual →

    • Fragmen of hyphae

    • Asexual spores →

      • Conidiophore - not enclosed in a sac

      • sporangiophore - enclosed in a sac

  • Sexual →

    • Gamete formation →

      • sexual spores

Yeasts

yeast - non-filamentous, unicellular fungi

• reproduce by budding yeasts & binary fission yeasts

• Facultative anaerobes

Dimorphic fungi: two forms of growth

• Di = two, morphic = shape

• grows as mold or yeast; depends on temp (25ºC: mold like, 37ºC yeast like)

• feature of many pathogenic fungi

Fungal disease → mycosis →

• systemic - throughout the body

• cutaneous - shallow part of the skin (EX: athlete’s foot)

• subcutaneous - deeper or underneath the skin

  • Cutaneous or subcutaneous are called dermatophytes because they feed on skin or dead skin cells (DERMA)

Lichens

Fairly harmless and don’t cause disease in humans

Lichens - fungi that have a mutualistic relationship with algae or cyanobacteria

• Diverse with more than 13,000 species

• Often the first life forms to inhabit newly exposed soil or rock. Also found on trees, concrete structures, roof tops.

• Think a fungi mixed with algae or cyanobacteria

Growth: lichen thallus (body) grows as fungal hyphae grow around the algal cells (forms the medulla)

• Rhizines - hyphal projections below the body; anchors the lichen

• Cortex - protective covering of hyphae

Fungus receives carbohydrates from alga; algae receives attachment and protection

Lichens can be indicators of air quality, food source for animals, and some produce antimicrobials.

Algae

It is not algae themselves that can harm of cause sickness to humans. It’s the toxins they produce

• Eukaryotic photoautotrophs lacking plant tissues

• Reproduce asexually/sexually

• Multicellular: brown (kelp) & red algae, green algae

• Unicellular (plankton): dinoflagellates; diatoms → these ones are the problems

  • Eutrophication causes a burst of these dinoflagellates creating a red tide

  • Agal disease - not infectious, disease ingestion of toxins

    • Dinoflagellates create a saxitoxin that’s eaten by and concentrated in sea life. When we eat these sea life, it causes harm through that build up of toxins

    • Neurotoxin - red tide from eutrophication → saxitoxin

      • Ciguatera - foodborne illness; in fish containing toxin

    • Diatoms - domoic acid toxicosis

Protozoa

Protozoa - unicellular eukaryotes, mostly aerobic heterotrophs

• some anaerobic types, a few photosynthetic

Characteristics:

• Motility via:

  • Flagella/flagellum

  • Cillia

  • undulating membrane

  • Pseudopods

• Nutritional structures:

  • Digestion in vacuoles

  • Ciliates: intake of food via cytosomes

  • Amoeba: pseudopodia

• reproduce asexually → fission/budding/schizogony (nuclei divide in cell)

  • Schizogony - cell full of nuclei where the nuclei divide

• reproduce sexually → via conjugation/via union of gametes

  • not transferring plasmids but gametes

• Some produce cysts under adverse conditions (encystment)

  • cysts are kind of the more dormant and resistant form in the environment that humans will then ingest

Cyst formation (Not mentioned much in the lecture but I don’t know if it’ll be on the test)

• When the protozoan feels the environment become unfavorable (temp, ph, etc), it enters the process of encystation → protozoan secretes a thick, protective wall around itself, creating a cyst. → inside the cyst, the protozoan stops or slows down its metabolism in order to allow it to stay in the cyst for long periods of time

• When the environment becomes favorable, the protozoan goes through excystation → cysts break open, allowing the protozoan to go on as normal

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Apicomplexa - protozoan group possessing complex life cycles

• Are obligate intracellular parasites → parasites that need to reproduce and live in the host in order to survive.

• Contain a number of pathogens → plasmodium spp (malaria)

• Malaria process:

  • Anopheles mosquito - carries sporozoite form (infective) in saliva

  • Sporozoites → form multiple merozoites (progeny) via schizogony in liver cells

  • Merozoites → infect red blood cell; become trophozoites (feeding stage)

  • Some merozoites develop into gametocytes; picked up by Anopheles bite

Terms part of the life cycle

• Schizogony - mitosis to form numerous merozoites

• Gamogony - mitosis and maturation of gametes

• Sporogony - mitosis to form sporozoites within mosquito cells

Helminths

• Multicellular eukaryotic animals

• Specialized to live in hosts

  • May lack digestive system

  • reduced nervous system

  • reduced or lacking locomotion

  • complex reproductive system: can have complex life cycle; multiple hosts to complete each larval stage

Parasitic worms →

• Platyhelminthes (flatworms) →

  • Trematodes (flukes)

  • Cestodes (tapeworm)

• Nematodes (roundworms)

Trematodes

• Flat, leaf-shaped; have ventral and oral sucker

• absorb food through cuticle covering

• Both vertebrate & mollusk host in life cycle

• named for host tissue in which adult form lives

  • Paragonimus spp. - lung fluke, Schistosoma - blood fluke

Tapeworm

• Scolex - head that has suckers for attachment

• absorb food through skin (cuticle)

• Proglottids - body segments making up the tapeworm

  • As it grows, it adds these proglottids and grows longer

  • contain male and female reproductive organs

Platyhelminth pathogens

• Schistosomiasis (blood fluke, Schistosoma)

• Lung fluke (Paragonimus spp): contaminated shellfish

• Tapeworms (Taenia spp): eggs are generally ingested through food, water, or soil contaminated with human or animal (host) feces

Nematodes

Roundworms

• Cylindrical; complete digestive system

• Dioecious; males contain spicules

• Free living and parasitic

Nematode pathogens

• Eggs infective - Ascaris; pinworm (Enterobius); whipworm (Trichuris) → found in intestines of human hosts

• Larva infective:

  • hookworm (Necator) - intestinal parasite

  • Trichinellosis - undercooked meat of infected animal

  • Heartworm (dirofilaria)