Lab 3: Macroscopic And Microscopic Observations Of Microorganisms Flashcards
What are the visual characteristics that differentiate Bacillus megaterium and Escherichia coli colonies?
B. megaterium colonies are large pearly mucoid, while E. coli colonies are much smaller
Macroscopic and microscopic differences include B. megaterium being gram-positive rods and E. coli being short gram-negative rods.
What terms do microbiologists use to describe macroscopic colony characteristics?
- Size
- Abundance
- Form
- Elevation
- Margin
- Surface
- Opacity
- Pigmentation
These terms help differentiate between various bacterial colonies.
What are the beneficial roles of fungi?
- Decomposition of matter
- Mycorrhizae systems providing nutrition to plants
- Source of antibiotics (e.g., penicillin)
- Used in fermentation of food products (e.g., bread, wine, beer, cheese)
Fungi play crucial roles in ecosystems and human industries.
What are the two main categories of fungi?
- Yeasts
- Molds
Some fungi are dimorphic, meaning they can exist in both forms.
Which yeast is commonly used in the production of beer, wine, and bread?
Saccharomyces cerevisiae
This species has been observed in laboratory settings.
What is the average size of yeast compared to bacterial species?
Yeast: 4-12 µm; Bacteria: 0.5-2 µm
Size is a distinguishing feature in wet mounts and Gram stain samples.
What is mycelium?
A tangled network formed by hyphae in molds
Mycelium gives molds their characteristic fuzzy appearance.
What are the six major phyla of fungi?
- Basidiomycota
- Zygomycota
- Chytridiomycota
- Ascomycota
- Microsporidiomycota
- Glomeromycota
These phyla encompass a wide variety of fungal species.
Which phylum do true mushrooms belong to?
Basidiomycetes
This phylum includes fungi that produce fruiting bodies.
What is the significance of Ascomycetes in veterinary microbiology?
- Includes the genus Penicillium, source of penicillin
- Contains pathogenic bacteria like Microsporum and Trichophyton
Dermatophytes from this group can cause ringworm.
What is the danger posed by Aspergillus flavus?
It can produce aflatoxin, a mycotoxin that causes liver damage and cancer in livestock
Mycotoxins are harmful compounds produced by certain fungi.
What is the purpose of obtaining pure cultures in microbiology?
To understand the biological and biochemical activities of microorganisms
This is crucial for controlling pathogenic microbes.
How can media be classified in microbiology?
- Undefined
- Defined
- Selective
- Differential
Each type of media serves different purposes in culturing microbes.
What is selective media used for?
To inhibit the growth of most bacteria while allowing a select group to grow
This media enriches for specific bacterial species.
What does differential media contain?
A chemical compound that changes appearance in the presence of specific bacterial groups
This helps in detecting specific bacteria.
What is the streak plate method used for?
To isolate individual microbial cells on agar medium
This method helps in obtaining pure cultures.
What is the role of lactic acid bacteria (LAB) in microbial communities?
They produce lactic acid and can grow at lower pH levels
LAB are often abundant in environments like silage.
What happens when sodium azide is used in culture media?
It inhibits cytochrome oxidase, blocking the electron transport chain in aerobic organisms
This allows LAB to grow in selective conditions.
What should you observe when examining silage macroscopically?
Smell (acidic, sweet, foul), appearance of vegetable matter, fluid, and surface/air interface
Macroscopic observations provide insight into microbial activity.
What is the incubation temperature for APT-azide cultures?
37°C for 2-4 days
This temperature is optimal for the growth of many bacteria.
Fill in the blank: The edge of a colony is referred to as the _______.
Margin
Colony morphology includes examining the margin for distinctive features.
What are the macroscopic characteristics to describe when observing colonies?
- Shape
- Color
- Size
- Unusual characteristics
Detailed descriptions aid in microbial identification.
