Ch. 7 Advanced
Assuming you start with just one microbe and it could divide every 30 minutes, how many microbes would you have after 2 hours?
16
Cell population growth can be represented by the number ______ with an exponent, where the exponent increases by ______ in each generation.
2; 1
Escherichia coli has a generation time of 20 minutes. If 1 million parent cells were placed in a flask of sterile nutrient broth and incubated under optimal growth conditions, approximately how many cells would be present in the broth after 1 hour?
8 million
Which of the following describes a relationship where microorganisms compete for survival in a common environment?
Amensalism
Which relationship does not require a particularly close association between microbes or between microbes and other organisms?
Amensalism syntropy
What term is used to describe a continuous culture system that provides nutrients and removes waste to stabilize cell cultures?
Chemostat
Which of the following is NOT part of binary fission? Septum formation completes and cell membrane patches. Daughter cells separate. Septum begins to form and chromosomes are pulled to opposite sides of the cell. Chromosomes line up so that crossing over occurs. Cell components enlarge and bacterial chromosome is duplicated.
Chromosomes line up so that crossing over occurs.
_______ is the process by which a change in one symbiotic partner leads to a change in the other, which may in turn lead to change in the first partner, and these changes can continue to occur over time.
Coevolution
What common term describes the single bacterium in an original sample that gives rise to a colony on a plate?
Colony forming unit
Which of the following is defined as a relationship between organisms where one benefits and the other is unharmed?
Commensalism
_______ is a type of symbiotic relationship between two organisms in which one species derives benefit without harming the other.
Commensalism
_______ is the term used to describe a situation where organisms gain mutual benefit from their association but can survive independently outside the partnership.
Cooperation
After a bacterial culture acclimates to a medium, the bacteria will divide in what type of pattern?
Exponential
Microbes are most susceptible to antimicrobial agents during which growth phase?
Exponential phase
A Coulter counter can count viable cells as well as determine their size. T/F
F
True or false: A Coulter counter can differentiate between living and dead or gram-positive and gram-negative organisms.
F
True or false: A person shedding bacteria in the late stages of infection is more likely to spread it to others than a person in the early or middle stages.
False
Which best describes a parasitic relationship between microbe and host?
Flesh-eating bacteria on human skin
Which term describes the length of time of a microbial species needs to divide?
Generation time
What term is used to describe a graphical representation of a change in population size over time?
Growth curve
What are the compounds that are released by members of a biofilm that accumulates as the population grows and stimulate gene expression in its members?
Inducer molecules
Which is FALSE regarding binary fission? Daughter cells are identical to each other. Binary fission occurs only once in the life of a single cell. It leads to genetic variation. It is a type of asexual reproduction.
It leads to genetic variation.
Which of the following characterizes the lag phase of a normal bacterial growth curve?
Little increase in cell numbers
______ is a type of symbiotic relationship between two organisms in which both species benefit.
Mutualism
Which of the following describes a type of symbiotic relationship between two organisms in which both species benefit?
Mutualism NOT: Symbiosis Reason: Symbiosis refers to any close relationship between two organisms, not necessarily the specific one described here. Commensalism Reason: Commensalism is a relationship between two organisms where one organism benefits and the other is unharmed. Parasitism Reason: Parasitism is a relationship between two organisms where one organism benefits and the other is harmed.
Which term best describes the association between a human host and the normal microbiota that aids in digestion?
Mutualistic
Real-time ______ can be used by scientists to quantify bacteria without culturing or isolating them.
PCR
Which of the following detection methods rely on nucleic acids for detection?
RT-PCR
Why is refrigeration of leftover food an effective way to prevent spoilage?
Refrigeration temperatures are not optimal for reproduction and growth of food-associated pathogens.
During which phase of growth does the number of new cells balance the number of declining cells?
Stationary phase
Which term describes any close relationship between two organisms?
Symbiosis
_________ is a close association between individuals from two species that may be helpful, harmful or neither to both members.
Symbiosis
A closed culture system is used to determine a population growth curve. T/F
T
Syntrophy and amensalism typically occur between different species of microbes. T/F
T
Syntrophy occurs when microbes share a habitat and feed off of substances made by each other, but this relationship is not necessary for their survival. T/F
T
The direct cell count, using a flow cytometer, can determine both viable cell numbers and number of dead cells in the sample. T/F
T
The time that it takes for a freshly inoculated agar culture to develop visible colonies is principally governed by that species' generation time. T/F
T
True or false: Biofilms are very common.
T
True or false: Microbes in the exponential phase of growth are more vulnerable to antimicrobial agents than those in the lag or stationary phases of growth.
T
True or false: Population growth can be calculated mathematically.
T
True or false: The rate of growth in a bacterial culture can be measured in hours, days, or weeks depending upon the species.
True
What term is used to describe the cloudiness of a broth culture?
Turbidity
Identify the ways that salt and/or sugar inhibit microbial growth. Multiple select question. Weakening the molecular structure of DNA Prevention of nutrient uptake Conversion to compounds with anti-microbial activity Interfering with bacterial motility Reducing the water activity needed for survival and growth Increasing osmotic pressure
Weakening the molecular structure of DNA Conversion to compounds with anti-microbial activity Reducing the water activity needed for survival and growth Increasing osmotic pressure
A relationship where microorganisms compete for survival in a common environment is known as _______
amensalism
Actinomycetes produce an antibiotic that inhibits growth of fungi
amensalism
Antibiotics released by one microbe to inhibit or kill other microbes demonstrates an antagonistic relationship called _________
amensalism
In one form of amensalism, microbes release specific chemicals called ______ into the environment to inhibit or kill other microbes.
antibiotics
A _______ is a complex association of microorganisms in which the members are bound to each other and a substrate by an extracellular matrix.
biofilm
Most microbes on earth live in a complex, organized association known as a(n) _________.
biofilm
When organisms attach to a substrate and secrete an extracellular matrix, a _______ is formed.
biofilm
A ______ is a continuous culture system that provides nutrients and removes waste to stabilize the growth rate and cell number of cultures.
chemostat
A genetic or evolutionary change in one symbiotic partner that leads to a genetic or evolutionary change in the other symbiotic partner is known as ________.
coevolution
Differences in the bacteria found in the GI tract of humans compared to those found in the GI tract of primates is most likely an example of __________.
coevolution
In the viable plate count method, a measured sample of a culture is evenly spread across an agar surface and incubated. Each __________ on the agar surface represents one __________ from the sample.
colony; cell
Colonies of Haemophilus clustered around growth of Staphylococcus
commensalism
A nondependent form of mutualism, where both partners can survive independently outside the relationship is called ______.
cooperation
A __________ ________ electronically scans a culture as it passes through a tiny pipette in order to obtain a cell count, but cannot differentiate between living and dead cells..
coulter counter
The ________ ________ count is obtained using a procedure that involves counting the number of cells in a sample microscopically using a special calibrated slide with a premeasured grid.
direct cell
Which of the following bacterial growth phases correlates to the acute stages of a bacterial infection?
exponential
A _________ ________ electronically scans a culture and counts live and dead cells tagged with fluorescent antibodies and can differentiate between gram positive and gram negative cells.
flow cytometer
When it is important to count the number of cells, determine cell size and differentiate between dead and live cells a/an __________ is used.
flow cytometer
A(n) ________ can scan a culture of bacteria or a sample of blood and differentiate between blood cells. viable plate count flow cytometer real-time PCR Coulter counter spectrophotometer
flow cytometer Coulter counter
The formula Nf = (Ni)2n is a mathematical formula representing bacterial ________.
growth
Molecules released by members of the biofilm that accumulate as the population grows and stimulate gene expression in its members are called ________ molecules
inducer
Microbes normally exist in which of the following locations on or in the human body?
intestines genitourinary tract mouth
During the ______ phase of microbial growth, numbers of cells are difficult to count because cells are adjusting to growth media, they have not reached their maximum growth rate, and the overall number of cells is sparse.
lag
________ phase is when a bacterial cell is placed into a new environment and cell division is slow.
lag
Put the phases of a normal population growth curve in order.
lag log stationary death
Lactobacilli are part of the natural microbiota found in the vaginas of females. The bacteria feed off of glucose molecules produced by the female and ferment them to lactic acid. This reduces the pH of the vagina to a level that cannot be tolerated by other more harmful bacteria. This relationship can best be described as __________.
mutualism
Nitrogen-fixing bacteria growing on plant roots
mutualism
The E. coli that normally live in the human large intestines and produce vitamin K that the body uses would be best termed a __________ relationship.
mutualistic
An association where a parasite spends all or most of its life cycle gaining nutrients and support within a host cell is called ______ parasitism.
obligate intracellular
Salt or sugar can be used to increase ______ that will restrict the growth of bacteria in foods.
osmotic pressure
A symbiotic relationship where one organisms benefits at the expense of another is termed ____.
parasitism
Plasmodium growing inside red blood cells
parasitism
______ is a relationship between two organisms where the host is harmed and the colonizer benefits.
parasitism
A critical number of members required in a group, such as a minimum number of cells in a population, is referred to as a(n) _________
quorum
_______ sensing is the ability of some microbes to detect the number of other microbes and act accordingly.
quorum
Which terminology describes the ability of some microbes to detect the numbers of other microbes and alter their behavior?
quorum sensing
The general term used to denote a situation in which two organisms live together in a close partnership required by one or both members is __________.
symbiosis
Limited growth during the lag phase of a growth curve is due to the need for cells to
synthesize new enzymes to metabolize nutrients in the culture media.
A beneficial relationship involving communal feeding between organisms sharing a habitat is called _________
syntrophy
A relationship in which the products given off by one organism are usable as nutrients for another organism is called ______.
syntrophy
Which relationships do not require a close association between microbes? syntrophy commensalism amensalism parasitism mutualism
syntrophy amensalism
In a normal bacterial growth curve, what quantity is represented on the x-axis?
time
Enumeration of bacteria can be achieved by the __________ cell count, in which a cell suspension in a chamber is viewed under the microscope.
total
