MRS Mold Biology & Identification 2 — Questions and Answers
Question 1: Which cellular structure is responsible for producing mold spores asexually?
- Rhizoid
- Conidiophore (Correct answer)
- Sporangiophore
- Ascus
Correct answer: Conidiophore
Conidiophores are specialized hyphal structures that produce conidia (asexual spores) in many common mold species.
Question 2: What is the primary function of melanin pigment in mold cell walls?
- Nutrient absorption
- Reproduction signaling
- Protection against UV radiation and desiccation (Correct answer)
- Enzyme production
Correct answer: Protection against UV radiation and desiccation
Melanin in mold cell walls provides protection against UV radiation, desiccation, and host immune responses.
Question 3: Which mold genus is characterized by a flask-shaped perithecium as its sexual reproductive structure?
- Aspergillus
- Penicillium
- Fusarium
- Chaetomium (Correct answer)
Correct answer: Chaetomium
Chaetomium produces flask-shaped perithecia with characteristic hairy appendages, making it a common indicator of water damage.
Question 4: A mold sample shows hyphae with regular cross-walls dividing the filament into compartments. These walls are called:
- Rhizoids
- Septa (Correct answer)
- Stolons
- Sporangia
Correct answer: Septa
Septa are cross-walls that divide hyphae into separate cells, distinguishing septate fungi from coenocytic (non-septate) fungi.
Question 5: Which of the following describes the 'xerophilic' characteristic of certain mold species?
- Preference for high-temperature environments
- Ability to grow at very low water activity levels (Correct answer)
- Requirement for direct sunlight
- Dependence on wood substrates
Correct answer: Ability to grow at very low water activity levels
Xerophilic molds can grow at water activity (aw) levels as low as 0.70–0.75, allowing them to colonize seemingly dry materials.
Question 6: Stachybotrys chartarum is classified as a 'hydrophilic' mold, meaning it requires:
- Water activity above 0.93 (Correct answer)
- Temperatures above 30°C
- Cellulose-free substrates
- Exposure to light for germination
Correct answer: Water activity above 0.93
Stachybotrys chartarum requires very high water activity (above 0.93) and is only found after prolonged, significant water intrusion.
Question 7: When viewed under a microscope, Cladosporium conidia appear in what characteristic arrangement?
- Single spherical spores in clusters
- Branching acropetal chains (Correct answer)
- Unbranched basipetal chains
- Star-shaped single conidia
Correct answer: Branching acropetal chains
Cladosporium produces branching chains of conidia in an acropetal (youngest at tip) arrangement, appearing tree-like under the microscope.
MRS Mold Biology & Identification 2
Which cellular structure is responsible for producing mold spores asexually?