Chapter 9 - Microbial Growth Flashcards
The growth of individual cells is _________________.
Exponential
The exponential growth of individual cells is a simple consequence of the ___________________ nature of the growth process.
Autocatalytic
What do we mean when we say that exponential growth is the result of autocatalytic nature?
The process of growth involves the synthesis of new macromolecules from simple precursor molecules, which requires catalysts that are themselves macromolecules. Thus, growth involves the synthesis not only of new structures but also of new catalysts for growth as well. The catalytic capacity of the cell increases steadily through the life cycle and hence the absolute rate of growth increases as well
Be familiar with the following figure.
A common way prokaryotes divide is by _______________ ______________.
Binary fission
Cell division in most prokaryotic cells involves inward growth of a ___________________.
Septum
The mechanism controlling septation is still unclear, but it involves the ring of the protein __________ that assembles just below the cell membrane around the equator of the cell when DNA replication finishes.
FtsZ
________ is analogous to tubulin.
FtsZ
Some cells divide by _______________, an unequal division, or multiple fission.
Budding
What is multiple fission?
A few prokaryotes grow until the mother cell is many times the size of a baby cell and then undergo multiple rounds of division without any additional growth
The _______________ _______ is the period between the “birth” of a cell by division of its mother cell and its own division into two baby cells.
Interdivision time
What is the most common measure of growth rate?
Generation time
What is “generation time”?
The time it takes for a population to double in number
Growth rates typically vary over about a __-fold range.
10
Bacterial chromosomes replicate ___________________ from a _____________ origin.
Bidirectionally
Single origin
In bacteria, successive cell cycles can overlap. Why is this significant?
Because “grandma” E. coli, for example, began making chromosomes for grandaughter cells when the daughter cell was born
The ___ period is the amount of time it takes for the bacterial chromosome to be replicated.
C period
In the __ period, division ocurs.
D period
There is an obligatory period of __ minutes between the completion of chromosome replication and cell division.
20 minutes
There is no obligatory G1 period; however, when the enviornment constrains growth to a generation time longer than __ minutes, there is a period equivalent to G1, and as the growth rate gets ______________, the gap gets _______________ until it disappears entirely at a generation time of __ minutes.
60 minutes
Shorter
Shorter
60 minutes
As the population grows increasingly quickly, the ___________________ time for DNA replication is pushed back further in the previous cycle.
Initiation
What are two reasons for the rapid growth rates seen in bacteria?
- Dispense with G1
- Overlap their cell cycles
At what point are bacterial cells least able to handle stress?
Cellular division
Microbial population growth is normally measured by ____________________.
Spectrophotometry
A ___________________ is an instrument that shines light of a chosen wavelength through a specimen and determines the amount that gets through.
Spectrophotometer
Microbial population growth is __________________.
Exponential
What is the instantaneous growth rate proportional to?
The number of cells present
When are generation times calculated?
During the exponential phase of growth
How do can you calculate the doubling time or generation time (g)?
From a natural log plot
y = kN, where k is the growth rate constant and equivalent to the slope of the line
If N = 2, the point at which the population has doubled, the equation can be re-written as ln(2) = kg
Once k (slope) is determined, g or doubling time can be determined 0.6931/k = g
Populations enter ________________ phase when they run out of nutrients or accumulate toxic quantities of waste materials.
Stationary phase
Cells that have been in exponential growth for several generations are in ________________ growth.
Balanced
When do most mutations occur?
Stationary phase
You must be able to label a standard growth curve.
When should tests on bacterial cells be completed?
During log phase/exponential phase
Why should tests be done during the log/exponential phase?
A culture growing exponentially remains quite constant in all of its important properities (average cell size, macromolecular composition, etc), and physiological experiments done on such cultures are much more reproducible
