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What are the essential nutrients for bacteria?
- inorganic salts
- trace materials
What is the main source of energy for bacteria?
What are the inorganic salts?
What are the trace minerals?
What are the factors that affect bacterial growth?
- gas requirements
- osmotic pressure
Bacterial enzymes are _____.
Low temperatures _____ enzyme activity.
High temperatures _____ proteins.
Which bacteria are cold-loving (0-30 degrees C)?
Which bacteria are the most pathogenic (20 - 40 degrees C)?
Which bacteria are heat-loving (40-80 degrees C)?
require free oxygen
grow only in absence of oxygen
grow in absence or presence of oxygen
grow best in concentrations of oxygen that are lower than that of air
What is the optimum pH for most bacteria?
6.5 - 7.5
Are bacterial cell membranes semipermeable?
How does water pass through a cell?
in and out freely
Exposure to a hypertonic solution causes _____ of a bacterial cell.
Exposure to a hypotonic solution causes _____ of a bacterial cell.
What type of bacterial reproduction does bacteria have?
Describe binary fission.
- cell increases in size, elongates
- splits down the middle
- separates into two new cells
- nuclear and cellular materials are divided between the two
Under the right conditions, how long does it take for bacteria to reach adult size and divide?
15 - 30 minutes
When bacteria are introduced into a medium, they grow in four phases. What are the phases?
- lag phase
- logarithmic phase
- stationary phase
- death or decline phase
Describe the lag phase.
- when first inoculated
- do not immediately "take off"
- need to adjust to the medium, temperature, environment
Describe the logarithmic phase.
- population of bacteria is doubling at regular intervals
- cell division rate greatly exceeds the death rate
- cells produced are young, viable, and show the most typical characteristics
Describe the stationary phase.
- growth rate levels off as nutrients are exhausted
- growth rate equals death rate
- bacterial cells are most resistant during this phase
Describe the decline phase.
- death rate exceeds reproductive rate
- due to depletion of nutrients
- presence of toxic products of metabolism
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