Lecture 7: Bacteria Growth And Measurment Flashcards
What is bacterial growth?
Increase in cell number in a population
This growth is often measured in terms of population size over time.
What is binary fission?
Cell gets bigger in volume, chromosome is replicated, cell contents divided up & distributed, septum forms, cell divides and becomes 2 new daughter cells
This is the primary method of reproduction in bacteria.
What is the microbial growth curve used for?
To study microbial population growth in batch culture in a closed system
It plots the number of live cells versus time.
What are the 4 phases of microbial growth?
Lag Phase
Exponential/Log Phase
Stationary Phase
Death Phase
Each phase represents different growth dynamics and behaviors of the microbial population.
What does ‘g’ represent in the context of bacterial growth?
Generation (or Doubling) Time
It is the interval between complete divisions or doubling time.
What is the range of generation time for bacteria?
20 min. - 33 hr.
This varies widely among different bacterial species.
What is the formula for calculating the number of bacteria at a given time?
Nt = N0 X 2n
Where N0 is the original number of bacteria and n is the number of generations.
True or False: The growth rate is inversely proportional to the generation time.
True
A shorter generation time results in a higher growth rate.
What is a Colony Forming Unit (CFU)?
A unit used to estimate the number of viable bacteria in a sample
This is important for quantifying bacterial populations.
What are the temperature ranges for Psychrophiles?
0-20°C, optimum ≤ 15°C
These bacteria thrive in cold environments.
What is the optimum temperature range for Mesophiles?
15-45°C, optimum 20-40°C, human body 37°C
Most human pathogens fall into this category.
What is the effect of high temperatures on microbial growth?
High temperatures kill microbes
Methods include boiling, pasteurization, and using ovens or microwaves.
Fill in the blank: Refrigeration is typically at ______.
4°C
This temperature slows down bacterial growth.
Fill in the blank: Refrigeration is typically at ______.
4°C
This temperature slows down bacterial growth.
What is water activity (aw)?
A measure of the availability of water for microbial growth
Ranges from hypotonic (high aw) to hypertonic (low aw).
What are the pH ranges for Acidophiles?
Optimum pH 1.0-5.5
These bacteria thrive in acidic environments.
What are the pH ranges for Acidophiles?
Optimum pH 1.0-5.5
These bacteria thrive in acidic environments.
What type of bacteria are obligate aerobes?
Bacteria that must have O2 to grow
They rely on oxygen for respiration.
What are microaerophiles?
Bacteria that require a specific amount of O2
They thrive in environments with reduced oxygen levels.
How does radiation affect bacteria?
It damages DNA
Some bacteria have mechanisms to resist damage from radiation.
What types of food are preserved using gamma radiation?
Seafood
Fruits
Vegetables
Meat
This method helps eliminate pathogens and extend shelf life.
