Chapter 9 - The Study of Microbial Growth Flashcards
Microbial growth occurs at what two levels?
- Growth at a cellular level with increase in size
2. Increase in population
Division of bacterial cells occurs mainly through ______ _______.
Binary fission
Time required for a complete fission cycle is called the __________, or ________ time.
Generation or doubling
Populations exhibit ___________ growth.
Exponential
Generation times vary from _______ to ____.
Minutes to days
What is the equation for calculating population size over time?
Nf = (Ni)2^n
What does Nf stand for in the equation for calculating the population size over time?
Total number of cells in the population
What does Ni stand for in the equation for calculating the population size over time?
Starting number of cells
What does the exponent n stand for in the equation for calculating the population size over time?
Denotes generation time
What does 2^n stand for in the equation for calculating the population size over time?
Number of cells in that generation
In laboratory studies, populations typically display a predictable pattern over time. What is this called?
Growth rate
What are the stages in the normal growth curve?
- Lag phase
- Exponential growth phase
- Stationary phase
- Death phase
What are the methods of analyzing population growth?
- Turbidometry
2. Enumeration of bacteria
What is enumeration of bacteria?
- Viable colony count
- Direct cell count
- Using a cytometer
- Using a Coulter Counter
How do you measure direct cell count?
- Using a cytometer
2. Using a Coulter Counter
What are environmental factors that affect the function of metabolic enzymes?
- Temperature
- Oxygen requirements
- pH
- Osmotic pressure
- Barometric pressure
Lowest temperature that permits a microbe’s growth and metabolism
Minimum temperature
Highest temperature that permits a microbe’s growth and metabolism
Maximum temperature
Promotes the fastest rate of growth and metabolism
Optimum temperature
Optimum temperature below 15 degrees C; capable of growth at 0 degrees C
Psychrophiles
Optimum temperature is 20 - 40 degrees C; most human pathogens
Mesophiles
Optimum temperature greater than 45 degrees C
Thermophiles
- As it is utilized it is transformed into several toxic products
- Most cells have developed enzymes that neutralize those chemicals
- If a microbe is not capable of dealing with toxic oxygen, it is forced to live in oxygen free habitats
Oxygen
What are the two categories of oxygen requirement?
- Aerobe
2. Anaerobe
- Obligate aerobe
- Facultative anaerobe
- Microaerophilic
Aerobe
- Obligate anaerobe
- Aerotolerant anaerobes
Anaerobe
All microbes require some ______ _______ in their metabolism.
Carbon dioxide
Grows best at higher CO2 tensions than normally present in the atmosphere
Capnophile
Majority of microorganisms grow at a pH between __ and __
6 and 8
What are the exceptions for those that grow at a pH between 6 and 8?
- Obligate acidophiles
- Alkalinophiles
- Osmotic Pressure
Most microbes exist under _________ or ________ conditions
Hypotonic or isotonic
What are the exceptions for those that exist in hypotonic or isotonic conditions?
- Halophiles
- Osmotolerant
- Atmospheric Pressure
Most microbes live under ______ atmospheric pressures
Normal
What is the exception for those that live under normal atmospheric pressure?
Barophiles
What is an environmental factor that influences microbes?
Niche
