Bio 205 chapter 5
At what phase does broth become turbid and visible colonies appear on agar in the bacterial growth curve?
Log phase
At what point in the bacterial growth curve are bacteria the most vulnerable to antibiotics?
Log phase
At what stage of the bacterial growth curve are the bacteria dividing rapidly and the graph is rising in a straight line?
Log phase
In humans, at what stage of the bacterial growth curve are disease symptoms developing because the bacteria are causing tissue damage?
Log phase
Most of the human pathogens are
Mesophiles
You have isolated an organism from the human intestinal tract. It grows better when you capped the culture tube with a semipros plug than when you used a plug that is completely permeable to oxygen. This organisms should be classified as a
Microaerophile
Which of the following is not a limiting factor for the growth of microorganisms?
Not enough humidity
Which of the following types of media are examples of a chemically undefined medium, or complex medium?
Nutrient agar
The stomach protects us from a large number of microbes that might be in our because
Of its high level of acidity
As a culture of Clostridium enters the decline phase of the growth curve, the vegetative cells will have
Produced endospores
An organism that grows at 5 C is classified as a
Psychrophile
A mesophilic bacterium could
Reproduce at 37 C Produce human disease Grow at human body temperature
A soil sample is added to a culture medium that has been deigned to promote the growth of the genus Pseudomonas while inhibiting the growth of fungi. The test uses a
Selective medium
The agar in nutrient agar serves as a
Solidifying agent
Which of the following methods of measuring population growth is a direct count?
Standard plate count using a dilution series
There are some mesophilic bacteria that are salt tolerant. An example is
Staphylococcus
At what phase in the bacterial growth curve in a patient do antibodies from the immune system and phagocytosis by white blood cells affect the process of the disease?
Stationary phase
At what stage of the bacterial growth curve do the reproductive and death rates equalize?
Stationary phase
In a culture tube at what phase of the bacterial growth curve do available nutrients become scarce and waste products begin to accumulate?
Stationary phase
Which one of the following diseases does not involve endospores?
Syphilis
Which of the following conditions are most likely to affect the growth of bacteria?
Temperature, oxygen and pH
When relating generation time of microbes to disease, which is a correct general statement that could be made?
The faster the generation time, the shorter the incubation period
How does the GasPak system work?
The hydrogen in the GasPak reacts with oxygen in the presence of a catalysts to form water, thereby creating an oxygen-free atmosphere
In the log phase of growth
The number of cells in the population increase rapidly
How can you take a mixed unknown sample and separate out pure colonies to identify them?
The pour plate method of mixing the sample with melted agar, then poured into petri dishes and allowed to harden A sterila loop can take a sample and streak for solution onto an agar plate An individual colony can be subcultured onto another agar plate
Hyperthermophile
These have been found in seawater rom hot water volcanic events
Thermophile
These organisms are present in compost piles and hot springs
Barophile
They are able to withstand high pressure
Aerololerant
They are insensitive to oxygen and still grow well when oxygen is present
Acidophile
They can tolerate acidic pH 2.0 to a pH 9.5
Anaerobe
They do not or cannot use oxygen
Facultative anaerobe
They grow in either the presence of or a reduced concentration of oxygen
Psychrotroph
They organisms live at the bottom of the ocean
Capnophile
They require an atmosphere low in oxygen but rich in carbon dioxide
Halophile
They require relatively high levels of salt
Microaerophile
They survive in environments where the concentration of oxygen is relatively low
Mesophile
This group has most of the pathogens as they grow at body temperature
Obligate anaerobe
This group requires oxygen for metabolism, just like us
Which of the following statements about generation time is correct?
Under optimal conditions some prokaryotes have a very fast generation time of 20-30 minutes Some organisms have much slower generation times of 20-30 hours
An acidophils would grow best at a pH of
2
Under what conditions would you find vegetative growth from Clostridium botulinum endospores?
A vacuumed seal can of food
____ are important food producing bacteria because they can be used to produce dairy products like buttermilk, sour cream and yogurt from milk and cream.
Acidophiles
A selective medium is one that
Allows one type of bacterium to grow while inhibiting another type
How is asexual reproduction used in prokaryotic cells?
An increase in the population size with each cell being identical to the parent cell
How does cytokinesis work in prokaryotes?
An inward pinching of the cell envelop, tubular homolog is part of the fission ring
A bacterium that grows only at the bottom of a thioglycollate broth tube should be classified as
Anaerobic
Bacteria that can grow only in the absence of oxygen are said to be
Anaerobic
Psychrophiles and thermophiles differ with respect to their
Best temperature for growth
Archaea reproduce by a process known as
Binary fission
The process by which bacteria reproduce is known as
Binary fission
Which of the following diseases are all caused by endospore forming Clostridia?
Botulism Gas gangrene Tetanus
An example of a mesophile that is most frequently identified cause of infective diarrhea is
Campylobacter
Some organisms like Neisseria grow well in an atmosphere that is low in oxygen and rich in carbon dioxide. What is the best name for these organisms?
Capnophiles
In a bacterial growth curve, when the number of dying cells exceeds the number of new cells formed, what stage are they in?
Decline phase
Endospores are heat-stable resting forms of all of the bacteria listed below except
Escherichia coli
A bacterium that grows turbid throughout a thioglycollate broth tube should be classified as
Facultative
The interval time between successive binary fission of a cell or population of cells is known as the
Generation time
Endospores are found primarily in which kind of organism?
Gram-positive bacillus
Facultative bacteria are those that
Grow in the presence or absence of oxygen
What are organisms called that require high amounts of salts?
Halophiles
Endospores are very difficult to destroy. Because of this, which of the following techniques will work to get rid of them?
Heat them under high pressure for several hours
Under the conditions of bioterrorism where were endospores from Bacillus anthraces found?
Inside an envelop On the surface of the skin On the surface of machinery like in the mail sorting room
An important contribution was made to microbiology with the introduction of agar by Robert Koch. Which of the following statements about agar is correct?
It contains no essential nutrients It remains liquid until cooled below 36 C As a solid in a petri dish it is useful to isolate pure colonies
At what stage in the bacterial growth curve are the bacteria growing in size, storing nutrients, and synthesizing enzymes in preparation for binary fission?
Lag phase
At what stage in the bacterial growth curve are there no cell divisions occurring, because the bacteria are adapting to their new environment?
Lag phase
Which of the following is not one of the four phases of a bacterial growth curve?
Lead phase
A bacterium that grows only at the top of a thioglycollate broth tube should be classified as
aerobic
Most bacteria grow best as
neutral pH