BIOL 314 Module 1 (Pt. 2)

Mycology, parasitology, and antimicrobials (Lecture 2 starting on slide 7 and lecture 3)

Hyphae

• In fungi

• Filamentous cells that compose most of the vegetative growth of the organism

Septa

Divisions between hyphae

Cell wall composition of fungi

Contains chitin

Pathogenic fungi morphologies (three)

• Yeast (single cell)

• Mold

• Dimorphic

Membrane sterol present in fungi

Ergosterol

How does dimorphic fungi behave at different temperatures?

Mold-like at room temperature and yeast-like at body temperature

Describe this fungus morphology

Mold (septate hyphae)

Describe this fungus morphology

Mold (non-septate hyphae)

Describe this fungus morphology

Yeast

Mechanisms of fungal disease (three)

• Primary: Overgrowth of normal flora, inhalation of spores, traumatic

• Traumatic inoculation into skin (e.g., gardener is pricked by thorn on rose bush)

• Toxins (e.g., ingestion of aflatoxins)

• Allergic reactions (e.g., bronchopulmonary aspergillosis)

Aflatoxins

• Refers to a group of carcinogens and mutagens produced by mold

• Type of mycotoxins

• Most often produced by mold of the genus Aspergillus

• Children have lower tolerance than adults

Infection by which group of parasites (of the two main groups) increases eosinophil count?

Helminths

Two main groups of parasites

Helminths and protazoa

Why are parasitic infections often more difficult to treat than viral, bacterial, and fungal infections?

Parasite cells are more similar to human cells (as many are animals or animal-like protists), so it is difficult to find drugs that target aspects unique to the parasites without harming us

How does treatment using antiparasitic drugs differ from antibacterial drugs? Why is this necessary?

• Far longer course of treatment (often several months)

• Lower dose

• Since parasitic cells are quite similar to human cells, there is a higher risk of side effects

• Often static rather than cidal

Simple (1) vs. complex (2) parasite life cycle

1. Parasite requires only one host species to complete its life cycle

2. Parasite requires at least 2 host species to complete its life cycle

Do fungi or bacteria have a longer incubation period?

Fungi

Fungi are o_______ pathogens, meaning…

• Opportunistic

• Tend to cause infections in individuals with compromised immune systems, or who are on antibiotics

Why are fungi less likely to infect humans than other pathogens?

Slower reproduction → our microbiome can typically control the growth

Mechanisms of fungal disease (three)

• Primary: overgrowth of normal flora, spore inhalation, or traumatic innoculation of the skin

• Toxins (e.g., ingesting aflatoxins)

• Excessive immune response

Rank the following in terms of reproduction speed, from fastest to slowest: bacteria, fungi+parasites, viruses

Viruses, bacteria, fungi+parasites

Intermediate host

• The host in which asexual reproduction occurs

Definitive host

• Host in which the parasite reaches sexual maturity and sexually reproduces

• AKA primary host

• The final host

Reservoir host

• Host that maintains the parasite

• Is not harmed by the parasite

What causes tissue damage in parasitic infections (two)?

1. The parasite itself (some have teeth)

2. Host immune response

Differences between bacteria and animal cells that can be targeted by antibiotics

• Cell wall containing peptidoglycan

• 70s ribosomes (as opposed to 80s in animal cells)

• (Bonus) Different enzymes for replication and transcription

• (Bonus) Enzymes in the folic acid pathway (they synthesize their own folic acid, while we acquire ours through diet)

Differences between fungal and animal cells that can be targeted by antifungal drugs

• Cell wall containing chitin

• Membrane containing ergosterol (as opposed to cholesterol in animal cells)

Most common pattern of parasitic infections

Chronic

Most common pattern of fungal infections

Chronic (CHECK THIS; SKETCHY)

Where does movement originate in ameoba (with pseudopods)?

Where does movement originate in ciliates?

Where does movement originate in flagellates?

Where does movement originate in apicomplex sporozoite?

Plot twist, it doesn’t originate anywhere (no obvious means of locomotion)

Do protazoa multiply inside of the host?

Yes

Do helminths multiply inside of the host?

No

Are chronic parasitic infections always symptomatic?

No

Static vs. cidal

• Lowkey a myth according to more recent studies…

• Cidal kills the pathogen, while statics inhibits it from growing and reproducing (allegedly)

• “Indeed, every single ‘static' antibiotic on the market today kills bacteria—there are no antibiotics that inhibit growth but do not kill” (Spellberg et al., 2025).

β-lactamase

Enzyme produced by some bacteria; confers resistance to beta lactam antibiotics, such as penicillin, by destroying them

Rank the following methods of diagnosing bacterial infections by quality from highest to lowest (not necessarily speed or affordability): PCR, bacterial culture, and rapid antigen testing

1. Bacterial culture (takes minimum 48 hours)

2. PCR (often ideal middle ground; quick and accurate)

3. Rapid antigen testing (fastest and cheapest, but most prone to innaccurate results)

Are false positive or false negative results more common from rapid antigen tests?

False negative results

What type(s) of ribosomes do helminths (1) and protazoa (2) have?

1. 80s

2. 80s