Fungi: Molds and Cultures

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Questions and Answers

Which surface texture of fungal colonies is characterized as appearing mostly wrinkled?

Velvety or Silky (correct)

Granular or Powdery

Moist

Cottony or Woolly

What is a primary disadvantage of using KOH or LPCB in fungal colony sampling?

It can damage the vegetative spores.

It is not effective for systemic fungi sampling.

It limits sampling to reproductive spores only. (correct)

It destroys the morphology of the fungi.

Where is the best place to observe the pigmentation of fungi?

On the top surface of the medium

Under bright light

On the underside of the medium (correct)

In the surrounding environment

What is a primary advantage of the hair baiting technique in fungal culture sampling?

It does not destroy the morphology of the fungi. Signup and view all the answers

What is primarily observed when sampling fungal colonies?

The color of the pigmentation Signup and view all the answers

Which type of surface texture of a fungal colony is described as cottony or woolly?

A fluffy and soft texture Signup and view all the answers

What form do dimorphic fungi take at 37°C?

Yeast Signup and view all the answers

What is the optimum temperature range for saprophytic molds?

20-30°C Signup and view all the answers

Which feature is characteristic of molds?

Multicellular Signup and view all the answers

How long should fungal cultures be incubated for optimal growth?

21 days Signup and view all the answers

What type of reproduction do molds use?

Both sexual and asexual Signup and view all the answers

What is the standard incubation temperature for fungi?

30°C Signup and view all the answers

Which of the following is NOT a form of fungal growth?

Bacteria Signup and view all the answers

What factor can induce a dimorphic fungus to change its form?

Change in temperature Signup and view all the answers

What is the typical growth temperature range for parasitic fungi?

30-37°C Signup and view all the answers

What process forms a new yeast cell?

Budding Signup and view all the answers

What happens to a yeast bud once it has formed?

It remains attached until it splits. Signup and view all the answers

What is binary fission in the context of yeast?

A method where DNA is duplicated and the cell divides. Signup and view all the answers

Which of the following represents how a yeast cell duplicates its genetic material?

Replication Signup and view all the answers

Which type of diseases can Griseofulvin be used against?

Mycosis Signup and view all the answers

What type of bacteria can cephalosporin target?

Both Gram+ and Gram- bacteria Signup and view all the answers

What is typically true about higher fungi?

They can be consumed directly as mushrooms. Signup and view all the answers

How does a yeast cell ensure that each new organism receives DNA during division?

By duplicating and then splitting DNA. Signup and view all the answers

During mitotic division, what is the phase where the cell divides its cytoplasm called?

Cytokinesis Signup and view all the answers

Which characteristic describes budding in yeast?

It produces identical offspring. Signup and view all the answers

What type of hyphae do Penicillium exhibit?

Septate hyphae Signup and view all the answers

Which structure is characteristic of Rhizopus?

Sporangium Signup and view all the answers

What is the function of phialides in fungi like Penicillium?

Produce conidiospores Signup and view all the answers

Which of the following fungi has nonseptated hyphae with no rhizoids?

Mucor Signup and view all the answers

Which of the following statements is true about Phialophora?

It has septate hyphae. Signup and view all the answers

What are the structures in Rhizopus that support the sporangium?

Sporangiophores Signup and view all the answers

In which fungi are conidiospores arranged in chains?

Penicillium Signup and view all the answers

What type of hyphae is characteristic of Mucor?

Coenocytic hyphae Signup and view all the answers

Which fungal structure is flask-shaped and contains conidiospores?

Phialide Signup and view all the answers

What is the role of sporangiophores in fungi?

Support for the fruiting body Signup and view all the answers

What characteristic do dematiaceous fungi exhibit?

They produce melanin in their cell walls. Signup and view all the answers

What type of patients are most commonly affected by fungal meningitis caused by dematiaceous fungi?

Immunocompromised patients Signup and view all the answers

Where are dematiaceous fungi commonly found?

In pigeon droppings Signup and view all the answers

What is used to identify the capsule of Cryptococcus neoformans?

India ink wet mount Signup and view all the answers

What visual characteristic indicates dematiaceous fungi when hyphae are observed?

Brown color Signup and view all the answers

What does a clear halo against a dark background indicate in the India ink preparation?

The presence of a fungal capsule Signup and view all the answers

Which of the following describes the colonies of dematiaceous fungi?

Dark and pigmented Signup and view all the answers

What type of staining method is demonstrated by using India ink?

Negative staining Signup and view all the answers

What type of fungal infection can dematiaceous fungi cause?

Meningitis among immunocompromised patients Signup and view all the answers

A sample observed with brown-colored hyphae would most likely be categorized as what type of fungus?

Dematiaceous fungi Signup and view all the answers

Study Notes

Molds

Are multicellular
Have a filamentous, branching form
Grow at room temperature

Dimorphism vs. Monomorphism

Dimorphic fungi are able to exist in both mold and yeast forms
This change is usually triggered by environmental conditions, such as temperature
- For example, they exist as yeasts at 37°C (body temperature) and molds at room temperature
Thermally dimorphic fungi are an example of dimorphism

Fungal Cultures

Saprophytes (molds) have an optimal temperature for growth of 20-30°C
Parasitic fungi (yeasts) have an optimal temperature for growth of 30-37°C
The standard incubation temperature for fungal cultures is 30°C
Fungal cultures are incubated in a humidified environment for 21 days
Bacterial cultures require an incubation temperature of 37°C

Fungal vs Bacterial Cultures

Fungal cultures are clinically important in the diagnosis and treatment of fungal infections
Anti-fungal medications are used to treat infections caused by fungi

Fungal Reproduction

Fungi can reproduce sexually or asexually
- Asexual
  - Budding: a new cell is formed through mitotic division and remains attached to the parent cell until it splits
  - Binary fission: a yeast cell replicates its genetic material (DNA) and then divides into two parts, with each receiving one copy of DNA
Sexual: Involves the fusion of gametes or nuclei from two parent organisms, resulting in the formation of spores.

Dematiaceous Fungi

Produce melanin in their cell walls
Have a characteristic brown color when grown on agar
Have dark colonies and pigmented fungal elements
India Ink Wet Mount: used to identify the capsule of Cryptococcus neoformans (a dematiaceous fungus)
- CSF is examined by adding one drop of India ink
- The capsule appears as a clear halo against a dark background (negative staining)

Penicillium

Septate hyphae with a conidiophore that exhibits branching to form metulae
Brush-like conidiophore (metulae) give rise to phialides with conidiospores
Spores are arranged in chains

Phialophora

Septate hyphae with flask-shaped phialides with cup-shaped collarettes with conidiospores
NO CONIDIOPHORE

Rhizopus

Nonseptated hyphae
With rhizoids (root-like structures)
With sporangiophores (stalk-like structures)
With sporangium (sac-like structure)

Mucor

Nonseptated hyphae with no rhizoids
Sporangiophores arise singly with a sac called sporangium
Sporangium contains sporangiospores

Topography of Fungal Cultures

It's important to observe the surface texture and pigmentation of fungal colonies.
Surface texture can be:
- Cottony or woolly
- Velvety or silky
- Granular or powdery
- Moist
Pigmentation can be observed on the surface or on the reverse side of the culture medium
Cellophane Tape Preparation:
- Used to sample sporulating fungi
- A cellophane tape is placed on the fungal culture and lifted
- The tape is then put on a slide with KOH or LPCB
- It's good for sampling sporulating fungi but may not show hyphae or rhizoids
- Advantage: does not destroy the morphology of fungi
- Disadvantage: limited to sampling reproductive spores and not vegetative spores

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Description

Explore the fascinating world of fungi, focusing on molds and their growth conditions. Learn about dimorphism, the difference between fungal and bacterial cultures, and the significance of environmental factors in fungal growth. This quiz is ideal for students of microbiology and mycology.