Chapter 6 Growth and Culturing of Bacteria
the increase in the number of cells, which occurs by cell division
Bacteria generally divide by which two ways
1. binary fission
Which cell (prokaryotic or eukaryotic) follow a cell cycle?
How many circular chromosomes do most bacteria have?
What are the phases of growth found in standard bacterial growth curves
1. lag phase
2. log phase
3. stationary phase
4. decline (death) phase
phase of bacterial growth where cells are actively producing ATP preparing for cell division
phase of bacterial growth that is the period of greatest cell division
the time required for a population of cells to double
new cells are produced very near the rate at which cells die; cells begin to die due to a build-up of waste products and possible shortages of nutrients, oxygen, and water
fewer cells are able to divide and more and more cells die as conditions degrade
decline (death) phase
when cells exhibit unusual shapes [many cells may undergo this in decline (death) phase]
in decline (death) phase some genera of bacteria produce these for survival
generally formed when a single cell divides to produce a large number of cells
all of the cells in a colony descend from a single what?
How does a colony grow?
slower in the center and faster at the edges
Cells at the edges have a better advantage because of what?
because they have greater access to fresh nutrients and water and fewer waste products are located there
give three characteristics of E. Coli
* plump bacillus
* Gram -
* motile (peritrichous)
what is so bad about the killer strain of E. Coli 0157 H7
it shuts down kidneys and secretes intotoxins while alive
What is the generation time for the killer strain of E. Coli 0157 H7
prefers to grow where no oxygen is present but is able to adjust to and tolerate the environmental condition, but it can also live in other conditions
list five ways to measure bacterial growth
1. serial dilution and plate count
2. direct microscopic count
3. most probable number
5. turbidity (cloudiness)
this type of bacteria grows at the bottom of a solid medium
all cells remain on the surface of the solid medium (aerobe)
this method is used if you are not sure if it is aerobe or anaerobe
30 to 300 per plate
begins with an estimate, then dilutions and plates
most probable number
allows the cells in a sample to be dried and then weighed
dry weight measurement
the measurement of metabolic products in a sample can also be used indirectly to do what?
measure bacterial growth
what are the two major factors affecting bacterial growth
1. Physical factors
2. Nutritional factors
What are the physical factors affecting bacterial growth?
* oxygen concentration
* hydrostatic pressure
* osmotic pressure
examples of bacteria that grow best at their optimum pH.
Examples of bacteria that grow better at extreme or different body temperatures
examples of major groups of aerobes and anaerobes that affect bacterial growth
most vegetative cells can live only a few hours without this physical factor that affects bacterial growth
physical factor that affects bacterial growth that is exerted by standing water
As far as nutritional facts are concerned what factors affect bacterial growth
SPONCH (sulfur, phosphorus, oxygen, nitrogen, carbon, hydrogen)
some bacteria have special nutritional requirements and makes them hard to grow in a laboratory. These bacteria are known as what?
elements that are required in very small amounts are ions and are needed as cofactors
The type of enzymes and the number of enzymes present determine the what of an organism which normally has fewer types and numbers or enzymes than less nutritionally complex organisms
bacterial interactions affecting growth explain some peculiar adaptive aspects of bacterial bioluminescence
acts as a kind of "superorganism" with different cells responding differently within it
the formation of endospores
two genera known for producing endospores
Bacillus and Clostridium
normally produced due to deteriorating environmental conditions
The core (which consists of what) of an endospore contains what is needed to return to a vegetative cell when conditions improve
What are the two methods of obtaining pure cultures
streak plate method
pour plate method
method of obtaining pure cultures that uses agar plates
streak plate method
method of obtaining pure cultures that makes use of serial dilution
pour plate method
When we classify agar it can be what or what?
Natural or Synthetic
What are examples of natural culture media?
type of culture media that is classified by chemical make up
synthetic (defined or complex)
type of synthetic culture media that the ingredients and exact amounts are known
type of synthetic culture media that the ingredients are known, but the exact amounts may vary from batch to batch
type of culture media that is classified by how the agars are used
type of culture media that encourages one species and discourages others
type of culture media that you can see a pH or color change in
type of culture media that has extra vitamins and minerals added to it
minimize the chances that culture will be contaminated by organisms from the environment or that organisms, especially pathogens, will escape into the environment
what are the three ways to maintain cultures
a way to maintian cultures (not used for lab cultures) a pure culture that can be maintained indefinetly once an organism has been isolated
a way to maintain cultures that is a culture in which organisms are maintained in a dormant state
a preserved culture that maintains the organisms with the characteristics as originally defined
What is involution?
cells assume a variety of unusual shapes, which makes them difficult to identify (starts when the cell starts to die- death/decline phase)
Name at least two ways to measure bacterial growth
(any of the two will work)
serial dilutions & plate count; filtration; turbidity; most probable number; direct microscope count
What is meant by "generation time"?
the time required for a population of cells to double (can vary) (asyncronous)
What is selective medium?
one that encourages the growth of some organisms but supresses the growth of others
How do we obtain pure cultures? (the book listed two ways)
streak plate method
serial dilution and pour plate method
cell division in bacteria is primarily by the process of what?
Cell division in yeast occurs primarily by what?
The bacterial growth curve is divided into how many phases?
4 [lag, log, stationary, and decline (death)]
Lag phase is characterized by what
a great decrease in cell number
In stationary phase what happens to cell populations numbers?
they remain static
Endospores are most likely to be produced in great numbers in what?
The solidifying agent most commonly used in microbiological media is what?
the appropriate number of colonies to count when performing plate counts is
30 - 300
Most of the bacteria that cause disease in humans are _______.
Bacteria that prefers to grow between 25C and 40C are termed
An organism that prefers high concentrations of carbon dioxide is termed a _____.
An aerotolerant anaerobe:
requires low concentration of oxygen
The enzyme responsible for the breakdown of peroxide to water and oxygen is called ______.
A halophile requires high what for growth?
Bacteria that are difficult to cultivate due to special nutritional needs are termed what?
The process of an endospore becoming a vegetative bacterium is called what?
The spore coat is composed primarily of what?
MacConkey agar is what?
both selective and differential
A culture that has been freeze-dried is termed
Culture media that allows some microbes to grow but suppresses others is what?