5.8 - Growth of Bacteria Flashcards
(38 cards)
Define Colony
Population of cells arising from a single cell of endospore, or from a group of attached cells.
Define pure culture
Only one species or strain of bacteria
-Aids in ID by characteristic colony color, shape, texture, size
Define mixed culture
Multiple strains or species of bacteria
Explain Obligate Aerobes oxygen use and if they have SOD and Catalase
Have both SOD and Catalase
Example: Mycrobacterium tuberculosis
Explain Facultative anaerobes oxygen use and if they have SOD and Catalase
have both SOD and Catalase
Example: Escherichia coli
Explain Microaerophiles oxygen use and if they have SOD and Catalase
- Damaged by normal atm. levels O2 levels (above 20%), needs 2-10% O2 levels
- Usually has SOD and Catalase in very low concentrations
- Example Helicobacter pylori
Explain Obligate/Strict anaerobes oxygen use and if they have SOD and Catalase
Usually lack both SOD and Catalase
Example: Clostridium
Explain Aerotolerant anaerobes oxygen use and if they have SOD and Catalase
- Ignore O2
- Usually have SOD and lack Catalase
- Example: Propionibacterium acnes
Superoxide Dismutase oxygen derivatives reaction equation
2 (02) + 2H –> O2 + H202
Catalase oxygen derivatives reaction equation
2 H2O2 –> 2 (H2O) + 02
Define Fastidious
If the bacteria requires many micronutrients or growth factors, they are considered fastidious
Define Complex media
Supports growth of wide variety bacteria
-Example nutrient agar
Define Enriched media
Addition of sterols, blood, serum, serum, egg yolk
Example: Sheep blood agar, Chocolate agar
Sheep blood agar used for?
Most clinically important Gr+ and Gr-
Chocolate agar used for?
- Heated lysed blood
- Fastidious organisms such as Neisseria gonorrhoea or Haemophilus influenzae
Define Selective Media
Ingredients that inhibit growth of some organisms but allow others to grow
Mannitol Salt Agar (MSA)
- High Concentration of NaCl (7.5%)
- Inhibits growth of most organisms but permits staphylococci to grow.
- Yellow color on altar indicates the bacterial species can ferment mannitol.
MacConkey agar
- Bile salts, dye crystal violet
- Inhibits growth of gram positive bacteria and selects for gram negative (but not fastidious gram negative)
- Lactose fermenters and pH indicator, allows for differentiation of Gram negative based on their ability to ferment lactose (turns pink for lactose fermentors)
What are the four stages of the bacterial growth curve?
Lag, Log, Stationary, and Death phases
Define Lag phase of bacterial Growth curve?
Cells synthesizing new macromolecules
Define Log phase of Bacterial Growth curve?
- Cell growing and dividing at maximal rate possible given their genetic potential and the local environment.
- Dividing and doubling at regular intervals.
Define Stationary Phase?
- Total number of viable cells remains constant.
- Nutrient limitation, accumulation of toxic wastes, depletion of O2.
- Endospore formation
- Secondary metabolite synthesis. e.g. toxins, antibiotics
Define Death Phase?
Decrease in number viable cells often exponential
What is the best phase for harvest of useful products in the bacterial growth curve?
Stationary phase
