fungi, algae and protozoans

mycology

study of fungi

mycoses

diseases caused by fungi

mycotoxicosis

illness caused by inhalation, ingestion of mycotoxins produced by toxigenic fungi

toxicoinfection

produciton of toxin during infection

fungi

• eukaryotic, spore forming, heterotrophs

1. primarily terrestrail

2. primarily aerobic

3. sexual and asexual reproduction

4. cell walls usually composed of chitin

• reverse colony growth

reverse colony growth

growth viewed from bottom of different types of selective agar

true fungi

• major decomposers

• beneficial relationships:

  • increased nutrition for plants and animals

  • antibiotic, steroid, and food production

    • penicillin, griseofulvin, cyclosporin, cortisone, cheese

• bad relationship:

  • major plant diseases that negatively impact agriculture

  • animal and human disease

the fungi: nutrition and metabolism

• saprophytes: nutrients from decaying organic matter

  • engage in exodigestion

• most are aerobic “some are faculative”

  • candida albicans: yeast infections

  • trichophyton rubrum/microsporum canis: ringworm

yeast are single cell fungi

• single cell fungi and facultative

• asexual reproduction occurs by budding

  • budding occurs in nutrient rich situations

• sexual reproduction produces spores

  • indicates less favorable situations

the fungi: molds

• molds are multi-cellular filaments fungi

  • hyphae: filaments of a mold

  • mycelia (mycelium): tangled masses of hyphae

• filamentous fungi reproduce by:

  • sexual reproduction which produces spores

  • asexual reproduction:

    • fragmentation of mycelium where each segment can generate a new individual

    • some can engage in budding

YM dimorphism

• dimorphic fungi can switch from yeast form (Y) to mold form (M)

  • YM shift is caused by differences between two envrionments (in host vs. outside of host)

    • major trigger is a change in temperature

• animal infections: Y form in host & M form outside host

• plant infections: M form in the host & Y form outside of the host

the fungi: spores and hard times

• spores aid dissemination of fungi during hard times

  • dissemination relies on mechanical disturbances and strong air currents

    • small size makes spores buoyant so that they stay airborne for long periods of time

• spores can also be used to identify fungi

  • bright colors, “fluffy” textures, and shapes of fruiting bodies are genes diagnostic

mycotoxins: intoxication vs infection

• illness caused by ingestion of performed toxin is called intoxication with fungi generally called mycotoxicosis

• ergot is a fruiting body containing mycotoxin produced by claviceps

  • vasoconstrictive, hallucinogenic, causes amnesia

• alfatoxins are carcinogenic mycotoxins produced primarily by toxigenic aspergillus

  • high exposure can lead to liver impairment and liver cancer

    • urinalysis can detect mycotoxins

mycotoxin benefits

• currently over a thousand compounds have been derived from erogt ingredients

• during labor:

  • can increase timing and strength of contractions

  • help deliver the placenta

  • controls post delivery bleeding or post partum hemorrhaging

• some ergotamine mixtures have been removed from the market while others remain:

  • cabergoline which can still be used to treat hyperprolactinaeia

mycoses: aspergillus

• infections caused by fungi

• in chest x-rays:

  • shows clouded region

  • sputum sample shows the presence of mycelia

  • most immunocompetent people inhale thousands of aspergillus spores on a daily basis without any effect

fungi: black mold & airborne toxins

• black mold: stachybotrys

  • produce satra toxins: skin rash, pharyngitis, and leukopenia

• one of the fungi involved in “sick building” syndrome

• can cause “hypersensitivity pneumonitis”

  • mold infects the lungs and produces toxin(s) in the lungs

    • causes allergic response in addition to pathological intoxication and infection

      • inactivated spores are still toxic

histoplasmosis: mimics TB

• carried in bird or bat droppings

  • often contracted during/after windstorms or building collapses when fungal spores become airborne

• “endemic” in Ohio and Mississippi River Valley Regions

  • → regularly found in a certain area

• usually self-limiting but >90% of patients with an acute primary infection are undiagnosed

• growth resembles TB or cancer on x-ray

  • does not respond to bacterial antibiotics or chemotherapy

algae

• photoautotrophs

• some are hetertrophic

• some are bioluminescent (emit light)

• some cause serious health problems due to intoxication (in florida)

• structure:

  • cell wall

  • chloroplast

  • mitochondria

phycotoxins

• in general, phycotoxins are toxic chemicals that are synthesized algae

• cyanobacteria also said to produce phycotoxins but this short review is based on toxigenic eukaryotes

• toxin grouping is based on symptoms:

  • neurotoxic: consumption, inhalation, contact

  • paralytic: consumption

  • amnesic: consumption

  • ciguatera: consumption

  • diarrheic: consumption

• consumption of shellfish (mussels, clams, oysters, scallops) and finfish (grouper, red snapper)

algae that produce phycotoxins

• some algae produce phycotoxins that can cause toxicosis in human due to:

  • inhalation of phycotoxin during HABs

  • ingestion of phycotoxin contaminated food/water

  • dermal contact with phycotoxin laden water

    • diatoms

    • golden brown algae

    • dinoflagellates

dinoglagellates: Karenia brevis

• can be bioluminescent, photosynthetic, heterotrophic and not all are toxigenic

  • population explosions generate a rust color or red tide

  • some produce neurotoxins called brevetoxins

    • during blooms, becomes airborne due to wave action and can cause harmful intoxications in people, especially those with pulmonary issues

    • bioluminescence in dinoflagellates created during mechanical disturbance

dinoflagellate: pfiesteria piscicida

• produces a neurotoxin

• enter the system by inhalation and through cracks in teh skin

• inhalation or absorption of toxin can lead to irreversible neurological damage

• first reported cases occured in Chesapeake Bay watermen

  • displayed neurodegenerative symptoms

  • eventually some deaths were felt to be due to exposure to this neurotoxin

phycotoxins and harmful algal blooms: HABs

1. paralytic shellfish poisoning

• occurs when shellfish that have fed on toxic dinoflagellates or cyanobacteria are eaten

  • saxitoxin causes paralysis

2. amnesic shellfish poisoning

• occurs when shellfish that have fed on toxic diatoms or golden brown algae are eaten

  • domonic acid causes amnesia

toxins can also become airborne during wave action or due to the law of mass action and carried by wind

the protozoa

• moist or aquatic habitats

• most are free living and feed on bacteria and other microbes

• unique features

  • no cell wall have a pellicle

  • contractile vacuole: primitive kidney

quinine

• alkaloid derived from the bark of one species of cinchona tree and was originally used to treat malaria → fluoresce under UV light

• british developed “gin and tonic” a way for soldiers to ingest quinine in the push to prevent malaria infections in the troops

• dont know the active mechanism after 400 years of use

• still used today and its derivatives but new drugs have been developed

the protozoa: unique features

• anaerobic protozoa: have hydrogenosomes instead of mitochondria

  • hydrogenosomes produce H2 and ATP and proton motive forces but there is no ETC

  • multiple origins

  • not found with mitochondria in a cell

• protozoan parasites that have hydrogenosomes

  • trichomonas vaginalis: trichomoniasis

  • giardia lamblia: giardiasis

pyruvate → CO2, H2, Acetyl-CoA, ATP

hydrogenosomes

• difficult group of protozoa differ in their biochemical mechanisms, thus concerted evolution

• do not coexist with mitochondria

• not detected in eukaryotic organisms that have extended periods of an aerobic lifestyle during their life cycles

featured parasite: giardia lamblia → giardiasis

• 1# globally reported protozoa infection

• anaerobic parasite attaches to the wall of the intestines using a ventral sucker and prevents uptake of lipids resulting in greasy fishy smelling, loose stool

• beavers are primary source in back-packing and camping enthusiast that drink from outdoor streams

• acquired by fecal oral route of contaminated water

  • often self limiting, 50-80% asymptomatic

• treatment:

  • drugs that are activated in the presence of hydrogenosomes or dugs targeting other vital functions

the protozoa: cysts and dormancy

• formation and germination of cysts occur in some protozoan parasites but not all:

  • giardia, toxoplasma, cryptosporidium

  • cysts: tough resistant dormant resting structures that protect the parasite as it moves through the environment from one host to another and occurs with intestinal parasites

    • encystation: formation of cysts in response to decreasing nutrients

    • excystation: germination of vegetative form, trophozoite, triggered by return of favorable conditons

• other parasites that generate systemic infections exhibit spontaneous “periods of dormancy” during their lifecycles

  • triggers for conversion between dormant and nondormant forms are not well understood

  • however, in infected individuals even a small portion of dormant parasites can escape killing by antiparasitic drugs and then reemerge to continue the infection after treatment has stopped

parasites: protozoans of medical concern

• trypanosoma cruzi: chagas fever

• leishmania: leishmaniasis

• plasmodium: malaria

• crytosporidium

• toxoplasma: toxoplasmosis

• naegleria: PAM - primary amebic meningoencephalitis