Ch.4 Flashcards
Pure Culture
- population of cells derived from a single cell
- allows study of a single species
- Organisms may behave differently than in nature
- Only about 1% of microorganisms can be cultured
- Pure culture obtained using aseptic technique: Minimizes accidental introduction of other organisms
Which technique is used to isolate bacteria from a mixed culture into a pure culture?
Streak-plate method
Which polysaccharide derived from Red Seaweed is used to solidify media for bacterial growth?
- Agar used to solidify medium
Why is agar preferred over gelatin?
for its non-nutritive qualities, which allow for bacterial growth without being digested
In the growth curve of a bacterial population, at which phase are the bacteria rapidly increasing?
Exponential (log) phase:
- Cells divide at constant rate
– Generation time measured
– Most sensitive to antibiotics
During which phase of the bacterial growth curve does the total number of viable (live) cells decline?
Death phase:
- Total number of viable cells decreases at constant rate
- Exponential, but slower than cell growth
thermophile
- 45 C to 70 C
- love hot tempertures –> common in hot springs and compost heaps
What happens to proteins inside of bacteria that cannot survive these types of conditions?
- Proteins of thermophiles resist denaturing
- Thermostability comes from amino acid sequence
- Number and position of bonds that determine structure
obligate aerobe
organism requires O2 to grow
Facultative aerobes
use O2, but don’t require it
Obligate anaerobes
cannot use O2
Aerotolerant anaerobes
obligate fermenters (can grow in O2, but they don’t use it)
How do high concentrations of salt and sugar in food help preserve food?
- All microorganisms require water for growth
- Dissolved salts, sugars make water unavailable to cell
- If solute concentration is higher outside of cell, water diffuses out (osmosis)
- Some microbes withstand or even require high salt
Which are the 6 major elements that are needed to build organic molecules and biological bodies?
Carbon
Hydrogen
Nitrogen
Oxygen
Phosphorus
Sulfur
What is the definition of “growth factors” when it comes to bacterial growth?
organic molecules that an organism cannot synthesize; must be present in the environment
- Growth factor requirements reflect biosynthetic capabilities
– Most E. coli strains synthesize all cellular components from glucose; no growth factors needed
What do the prefixes “Photo” and “Chemo” mean when it comes to microbial nutrition?
Photo = use light as an energy source
Chemo = gain energy from inorganic compounds
Phototrophs
- Phototrophs obtain energy from sunlight
– Plants, algae, photosynthetic bacteria
Chemotrophs
- Chemotrophs extract energy from chemicals
– Mammalian cells, fungi, many types of prokaryotes extract energy from organic molecules
What do the prefixes “Hetero” and “Auto” mean when it comes to microbial nutrition?
Hetero = organisms incapable of making their own food from light or inorganic compounds
Auto = an organism that is self-nourishing or capable of generating its own food.
Photoautotrophs
energy from sunlight; carbon from CO
Photoheterotrophs
energy from sunlight; carbon from organic compounds
Chemolithoautotrophs
energy from inorganic compounds; carbon from CO2
Chemoorganoheterotrophs
energy and carbon from organic compounds
What is the function of “selective” media?
- Selective media inhibit growth of certain species in a mixed sample, while allowing growth of species of interest
