Fungi

What are the four major taxa of fungi of medical importance?

1. Pneumocystidomycetes: asexual trophic form 2. Saccharomycetes: asexual yeast cells 3. Eurotiomycetes: contains the haploid ascospores. 4. Sordariomycetes: contains teleomorphs

What are the essential differences between asexual and sexual reproduction?

Asexual Replication: mitosis only Produce anamorph spores Sexual Replication: meiosis, preceded by fusion of protoplasm and nuclei of two compatible mating types Produce teleomorph spores

What are the two types of asexual spores?

Asexual spores consist of two general types: sporangiospores and conidia. Sporangiospores are asexual spores produced in a containing a structure or sporangia and are a characteristic of genera belonging to the Mucorales such as Rhizopus and Mucor. Conidia are asexual spores that are borne naked on specialized structures as seen in Aspergillus, Penicillium and the dermatophytes

What are the main sites of action for antifungal drugs?

Cell wall- Echinocandins (glucan synthesis) Nikkomycin (chitin synthesis) Cell membrane- Azoles (ergosterol synthesis) Allymines (ergosterol synthesis) Polyenes (direct damage) Endoplasmic reticulum - Sodarins (protein synthesis) Azasordarins (protein synthesis) Nucleus - Flucytosine (nucleic acid synthesis) Griseofulvin (inhibition of mitosis)

What are conidia and what do they do?

Conidia are formed from aerial hyphae and used to disseminate the fungus

What are ascospores?

Created by Ascomycota Produced in sac called ascus Each ascus contains 8 haploid ascospores

What is ergosterol?

Ergosterol serves many similar actions as cholesterol in animal cells

What are the unique features of fungal cell walls?

Fungal cell walls are ridged and composed of chitin and glucan. The cell membranes contain ergosterol instead of cholesterol as the major component.

What is so special about the cell membranes and walls of fungi?

Fungal cell walls are ridged and composed of chitin and glucan. The cell membranes contain ergosterol instead of cholesterol as the major component.

In addition to morphology and genetic identification, what is another way to classify fungi?

Fungi are also characterized by molecular characteristics and mode of spore production

What is a key difference between fungal pathogens and viruses, archaea and bacteria?

Fungi are eukaryotes and have their own domain

What are hyphae? What are vegetative hyphae?

Hyphae are threadlike tubular structures that elongate at their tips by a process known as apical extension. Hyphae are either coenocytic (hallow) or septate (cross walls). Vegetative hyphae can grow on an agar or on other solid surfaces. It grows on or beneath the surface of the cultured medium.

What is MALDI - TOF MS?

MALDI- TOF MS uses species-specific patterns of peptides and protein masses to identify microorganisms. It has been shown to be highly accurate in identifying a broad array of bacteria and recently has been shown to provide a rapid and reliable tool for identification of yeasts, yeast-like fungi and molds. Form of mass spectroscopy that recognizes peptide secretions and creations Recognizes the 'fingerprint' and unique chemical composition

What is molecular mimicry and how might fungal pathogens use it?

Pathogen produces molecules similar to host molecules Fungi produces molecules that are functionally similar to host molecules

What does it mean to be primary pathogen?

Primary pathogens are capable of initiating infection in a normal apparently immunocompromised host. they are able to colonize the host, find a suitable micro environmental niche with sufficient nutritional substrates, avoid or subvert the normal host defense mechanisms and then multiply within the micro environmental niche.

What is dimorphism and why is it relevant for fungal pathogenesis?

Saprobic phase (hyphae) to pathogenic phase (yeast)

What are sporangia?

Sporangia are some sort of enclosure which produces and houses asexual fungal spores

How is a telomorph different from an anamorph?

Teleomorph Spores- Produced during sexual replication Anamorph Spores- Produced during asexual replication

What are the azoles?

The azole class of antifungals may be divided in terms of structure into the imidazoles (two Nitrogen's in the azole ring) and the triazoles (three Nitrogen's in the azole ring). Amongst the imidazoles only ketocaonazole has systemic activity. The triazoles all have systemic activity and include fluconazole, itraconazole, coriconazole, posaconazole, and isavucanazole. In general terms, what is the main mechanism of action for Echinocandins?

What's the prinicple classification feasture for yeasts and molds?

Yeasts are unicellular, while molds are multicellular

How might fungal pathogens be using diverse proteinases in pathogenesis?

help establish an infection neutralization of host defenses help allow entrance through skin mucosal barriers

What are some of the identifying characteristics that are helpful for fungal diagnosis?

morphological: looking for growth immunologic: looking for antibodies histopathologic : studying of tissues

How were fungi previously classified?

morphology and mode of spore production

How is this changing and what's a common method for classification now?

on biochemical and molecular characteristics

Are fungi often considered primary pathogens- why or why not?

some of them can be considered primary pathogens because they can infect immunocompromised individuals.

What does it mean to be saprophytic?

they live off dead or decaying organic matter.