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18 Cards in this Set

  • Front
  • Back
Define binary fission.
-most common means of reproduction by bacteria
-once cell divides into two, split to make four, which become eight, etc
Define lag phase.
-adjustment period of bacteria in new medium/environment
-no cell number growth, but increase size/girth
-increase rate of RNA, DNA, and ribosome production
Define logarithmic phase.
-cell numbers increase in exponential growth
-doublings occur at regular intervals
-the period of balanced growth in which the rates of synthesis of importnat componenets are maximized for condistions
-all units increase in equal intervals per time
-most cells viable
-largest sized cells due to largest number of ribosomes and proteins
Define total cell count.
-the sum of all living and dead cells
What are factors that affect the length of lag phase?
-status of transferred cells
-previous environment
-number of viable cells transferred
Define Viable Cell Count.
-Only the living cell count
When are cells most vulnerable to chemicals and antibiotics?
-logarithmic phase
What is the stationary phase?
-growth rate begins to taper off
-growth and death rates are equal
-bacterial growth reaches a plateau
-cells become smaller and old, nutrients become limiting and wastes accumulate
What is the death phase?
-lack of nutrients lead to starvation
-dead cells lyse which can serve as nutrients for other cells
What is the difference of solid media verses liquid in growth?
-solid medium has tightly packed cells leading to quicker use of resources
-outside of colonies are in exponential growth while center is in death phase
What is diauxic growth?
-growth of microorganisms in two phases
What is cryptic growth?
-cells in center of colony die releasing nutrients that viable cells can use
What is catabolite repression?
-breakdown of nutrients is inaccessible
-use of enzyme is needed for growth and can exhibit how a microorganism uses diauxic growth
What are two common ways to measure bacterial culture growth?
-plate count
-optical density
What is a plate count?
-using a plate or liquid culture of bacteria
-bacteria plated, incubated, and cells grown after 24 hours are counted for viable cells
-expensive and time consuming
What is the optical density method of bacterial count?
-measure of turbidity
-inexpensive and quick
-accuarate readings for log phase
-innacurate otherwise because of dead cells refracting light as well
What is generation time?
-doubling time
-the time required for the formation of two new cells from one cell
-dependent on the cells genetic ability to carry out catacolic and anabolic processes
How do you find the generation time from a graph?
-draw a straight line in log phase
-find any OD number on x-axis and draw line to y axis (mark as beginning value)
-double this time and find on y axis (mark end time)
-the distance between these two points horizontally is the doubling time