LT Bacteria Flashcards
What are the two types of bacterial media?
Broth: liquid medium, high cell concentrations, mixtures.
Agar: semi-solid, supports isolated colony growth for inspection.
Why is aseptic technique important?
Prevents contamination of cultures and tools.
Avoids growth of undesired microorganisms.
Ensures accurate experimental results.
How do Gram-positive and Gram-negative bacteria differ?
Gram-positive:
- Thick peptidoglycan layer.
- Stains purple/blue.
Gram-negative:
- Thin peptidoglycan + outer membrane.
- Stains red/pink.
What are some colony characteristics used in bacterial identification?
Shape:
Surface:
Color:
Texture:
Transparency:
Shape: Circular, irregular, filamentous, etc.
Surface: Smooth, rough.
Color: Pigmented or non-pigmented.
Texture: Glossy, matte.
Transparency: Translucent or opaque.
What metabolic capabilities can distinguish bacteria?
Nutritional modes: Chemoheterotrophs, photoautotrophs.
Oxygen requirements: Obligate aerobes, obligate anaerobes.
Enzyme production (e.g., amylase).
How can susceptibility to antibiotics identify bacteria?
Antibiotic sensitivity linked to cell wall structure or enzymes.
Clear zones of inhibition indicate sensitivity.
Helps determine effective treatment.
What steps are critical in creating a bacterial lawn?
Label plate underside.
Sterilize tools and avoid contamination.
Inoculate agar surface entirely.
Add antibiotic discs carefully.
What does a clear zone around a bacterial colony indicate in a starch agar test?
Presence of amylase enzyme.
Bacteria metabolize starch, preventing iodine staining.
What are the key features of bacterial growth and replication?
Binary fission: Bacteria divide every ~20 minutes under ideal conditions.
1 bacterium can produce 4 × 10²¹ clones in 24 hours.
Growth is limited in natural environments due to non-ideal conditions.
What are the natural habitats of E. coli and B. subtilis?
E. coli: Lower intestine of vertebrates (facultative anaerobe).
B. subtilis: Soil (obligate aerobe).
What is the purpose of storing agar plates upside-down?
Prevents condensation on the lid from dripping onto the culture.
Maintains sterile conditions.
What are the four nutritional modes of organisms?
Photoautotrophs
Chemoautotrophs
Photoheterotrophs
Chemoheterotrophs
Photoautotrophs: Use light and CO₂ (e.g., plants, some bacteria).
Chemoautotrophs: Use chemicals and CO₂ (unique to prokaryotes).
Photoheterotrophs: Use light and organic compounds (unique to prokaryotes).
Chemoheterotrophs: Use chemicals and organic compounds (e.g., animals, fungi).
What are endospores?
Resistant dormant cells produced by some species (e.g., Bacillus, Clostridium).
Allow survival in extreme environments.
What does the starch hydrolysis (amylase) test determine?
Tests for presence of amylase enzyme.
Positive result: Clearing around bacteria after iodine addition (starch hydrolyzed).
Negative result: No clearing, dark color indicates starch remains.
What are antibiotics, and where do they come from?
Produced by bacteria/fungi as evolutionary adaptations.
Many antibiotics are semi-synthetic or synthetic.
