Ch. 4 Microbiology Assignment Questions

Identify the first four stages of the growth curve that correspond to the numbers 1-4 on the figure: The 5th stage, or "phase of prolonged decline," is already given.

1. lag phase 2. exponential/log phase 3. stationary phase 4. death phase

Energy and carbon source of photoautotroph

Energy: sunlight, Carbon: CO2

Energy and carbon source of photoheterotroph

Energy: sunlight, Carbon: organic compounds

most probable number

a statistical estimation rather than a precise measurement of cell numbers

A(n) ___ requires only carbon dioxide as a sole carbon source

autotroph

For many hundreds of years, people have often preserved food by which of the following methods? a) refrigerating them to inhibit microbial growth b) adding large amounts of salt or sugar c) keeping the foods hydrated so they would not dry out d) sealing them raw in airtight containers

b) adding large amounts of salt or sugar

Which of the following is most likely to be a pure culture? a) a petri dish covered with bacteria following inoculation from a single patient b) a broth culture growing in a flask c) a single colony growing on a streak plate d) a bacterial lawn of growth covering an agar plate

c) a single colony growing on a streak plate

consumption of O2 by aerobic growth allows for

creation of a low O2 microenvironment

The amount of O2 in the Earth's atmosphere is about a) 79% b) 3% c) 95% d) 20%

d) 20%

___ media work by showing distinct reaction types, such as a color change in some colonies but not in others

differential

Media designed to highlight distinguishing characteristics of different organisms are called which of the following?

differential media

An organism that must consume organic matter is called a(n) ___

heterotroph

A(n) ___ is a microbe that prefers environments near or at a pH of 7

neutrophiles

production of metabolic wastes by one microbe allow

nutrients for another microbe

The viable plate method is based on the principle that each colony represents ___ cell or colony forming unit

one

A species grows most rapidly as its ___ growth temperature

optimum

If a solute concentration is higher outside the cell than inside the cell, water will diffuse out due to osmosis. This will result in ___

plasmolysis

pure cultures are

simpler to reproduce in the laboratory

A ___ medium means that the medium does not contain any viable microbes

sterile

In the ___-___ method, a small amount of culture or sample is spread over a solid medium with a sterile inoculating loop, gradually diluting the sample over the surface of the medium to yield isolated colonies

streak plate

Microorganisms that prefer hot environments (optimum temperature 45 C to 70 C) are termed ___

thermophilic

True or false: a pure colony is a distinct mass of microorganisms which develop from a single cell growing on a solid medium

true

Bacteria that require growth factors and complex nutrients are termed ____

fastidious

A ___ sensor can detect the slight decrease in pH that accompanies the production of carbon dioxide by various microorganisms

fluorescent

In binary fission, the doubling time of a particular microbial species is also known as its ___ time

generation

membrane filtration

good for concentrating dilute samples of cells

What term is used to describe essential organic compounds, such as a vitamin or amino acid, that must be provided in the diet?

growth factors

An extreme ___ specifically requires high concentration of salt for growth

halophile

Optimum environment for mesophile

human body

A microorganism that has a temperature optimum close to the boiling point of water is a

hyperthermophile

synthesis of toxic compounds

inhibits competitors

___ phase describes the initial phase after bacterial cells are placed into a new environment and are gearing up for cell division, but their numbers have not yet increased

lag

A container/tube of liquid or solid culture ___ provides the proper nutrients required for microbial multiplication.

medium

a microbe that requires small amounts of O2 (2-10%) for aerobic respiration but is inhibited by higher concentrations is called a(n) __

microaerophiles

A(n) ___ aerobe, or strictly aerobic organism, requires O2 for survival

obligate

bacteria cannot multiply if O2 is present, and are often killed by even brief exposure to air, are termed ___ ___

obligate anaerobes

direct microscopic count

rapid; involves a thin chamber that holds a known volume atop a microscopic grid

___ media are used to isolate specific types of microorganisms from saliva, feces, or any other sample that contains many microbial species

selective

MacConkey agar contains bile salts and dyes that inhibit Gram-positive organisms and Gram-negative cocci, making it ___; it also contains a pH indicator that turns pink-red when lactose in the medium is fermented, making it ___

selective, differential

plate count

time-consuming but technically simple; counts living cells only

Optimum environment for psychotroph

refrigeration

Function of iron

Part of certain enzymes

Function of potassium, magnesium, and calcium

Required for the functioning of certain enzymes

How do high levels of salt or sugar work to preserve food? a) they create a hypotonic environment that leads to plasmolysis of bacterial cells b) they reduce water availability, making it difficult for food spoilage microbes to grow c) they encourage growth of beneficial microbes, which outcompete food spoilage microbes

b) they reduce water availability, making it difficult for food spoilage microbes to grow

When bacteria or archaea are grown on agar plates or in tubes or flasks of broth, these closed systems are a ___ culture. By contrast, cells can also be grown in an open system, or a continuous culture.

batch

Many bacterial communities secrete polysaccharides and other hydrophilic polymers. This mesh-like accumulation can help protect the bacteria growing within from antibiotics or disinfectants. These communities are called ___

biofilms

Which of the following are true statements regarding reactive oxygen species (ROS) a) ROS are used by obligate anaerobes instead of O2 b) ROS are commonly found in anaerobic environments c) ROS are formed as byproducts of aerobic respiration d) ROS are toxic to obligate anaerobes which typically lack protective mechanisms e) ROS can damage cell components

c) ROS are formed as byproducts of aerobic respiration d) ROS are toxic to obligate anaerobes which typically lack protective mechanisms e) ROS can damage cell components

What are the advantages of using chemostat to keep microbial cells in a state of continuous growth? a) all five phases of growth are represented b) the chemostat is a good way to maintain sterility c) a uniform population of cells is maintained d) a constant growth rate and cell density can be maintained

c) a uniform population of cells is maintained d) a constant growth rate and cell density can be maintained

Many medically important aerobes are ___, meaning they require atmospheres that have additional CO2

capnophiles

Which enzyme converts hydrogen peroxide, formed in aerobic respiration, to water and O2?

catalase

A ___ is a continuous culture system that adds nutrients and removes waste in order to maintain a constant growth rate and cell density

chemostat

flow cytometer

detects the scatter of a laser beam as bacteria pass through a narrow channel

conditions in close microbial associations are

difficult to reproduce in the laboratory

In which group do most human pathogens belong? a) hyperthermophile b) psychrotroph c) thermophile d) psychrophile e) mesophile

e) mesophile

viable cell count

especially valuable when working with dilute samples, also for determining the number of living cells

True or false: a direct cell count typically determines only the number of live cells in a sample

false

True or false: as a result of exponential multiplication, a few cells of a pathogen may give rise to thousands in only a matter of hours

true

True or false: in a growth curve, cell numbers increase exponentially during the log phase and decrease exponentially during the death phase

true

True or false: the spread plate techniqure uses a sterile tool, such as an L shaped glass rod, to distribute the sample evenly around the surface of a plate

true

direct cell counts

useful for determining the total number of microbes, including living and dead, plus those that cannot be cultured

Function of nitrogen

Component of amino acids and nucleic acids.

Function of carbon, oxygen, and hydrogen

Component of amino acids, lipids, nucleic acids, and sugars

Function of phosphorous

Component of nucleic acids, membrane lipids, and ATP

Function of sulfer

Component of some amino acids

Identify any of the following which contain nitrogen a) RNA b) carbohydrates c) DNA d) proteins e) fats

a) RNA c) DNA d) proteins

Based on your current understanding of the microbial world, which of the following would you anticipate would need phosphorous? a) helminths b) viruses c) viroids d) bacteria e) prions

a) helminths b) viruses c) viroids d) bacteria

When working with anaerobes, what advantage does an anaerobe chamber give compared to an anaerobe container in terms of the needs of the microbes? a) the anaerobic chamber protects strict anaerobes that cannot tolerate even brief exposures to O2 b) the anaerobic chamber gives the researcher the convenience of more space to work c) the anaerobe container is cheaper and easier to use, but many more are needed to yield the same space

a) the anaerobic chamber protects strict anaerobes that cannot tolerate even brief exposures to O2

The streak plate technique works by using an inoculating loop to spread a bacterial sample in a pattern that thins it out, but this only works if: a) the inoculating loop is resterilized at each thinning step of the pattern b) the culture is poor to begin with c) the inoculating loop is sterilized only at the beginning of the pattern d) there is a new diluted sample added at each step

a) the inoculating loop is resterilized at each thinning step of the pattern

An ___ is an organism that prefers alkaline pH (pH above 7)

alkaliphiles

Which of the following describe selective media? a) display visible differences among microorganisms b) allow the growth of desired organisms c) inhibit the growth of certain species d) select for growth of a broad spectrum of organisms

b) allow the growth of desired organisms c) inhibit the growth of certain species

Animals could not survive without autotrophs because without them the world would run out of a) inorganic carbon b) organic carbon c) organic nitrogen d) inorganic nitrogen

b) organic carbon

Choose the best description of bacteria found during stationary phase of the growth curve a) the length of time cells spend in stationary phase is consistent within a species, regardless of environmental conditions, b) some cells utilize nutrients released by other dead cells in order to multiply c) secondary metabolites are not produced during stationary phase d) some cells in the population are dying e) the total number of viable cells remains relatively constant

b) some cells utilize nutrients released by other dead cells in order to multiply c) secondary metabolites are not produced during stationary phase d) some cells in the population are dying e) the total number of viable cells remains relatively constant

If you start with a single bacterial cell that has a generation time of 20 minutes, there will be ___ cells after 1 hour

8

Energy and carbon source of chemolithoautotroph

Energy: inorganic chemicals, Carbon: CO2

Energy and carbon source of chemoorganoheterotroph

Energy: organic compounds, Carbon: organic compounds

What are limitations of using a spectrophotometer to measure turbidity in order to determine cell numbers? a) a relatively high number of cells must be present to yield a turbid culture b) low numbers of bacteria result in a clear solution that cannot be counted c) results must be tested and correlated to a direct cell count method for each species and condition d) individual cells are counted as they pass a detector, so although automated, the process can take some time e) this method is very routine because it can be performed so rapidly

a) a relatively high number of cells must be present to yield a turbid culture b) low numbers of bacteria result in a clear solution that cannot be counted c) results must be tested and correlated to a direct cell count method for each species and condition

Microbial cells must maintain a near-neutral internal pH. Because of this, bacteria that grow in alkaline environments have mechanisms to __ a) bring protons into the cell b) pump out protons that enter the cell

a) bring protons into the cell

Viable cell counts determine the number of a) cells capable of multiplying b) total cells (live and dead) c) live cells

a) cells capable of multiplying

Which of the following are examples of an enriched complex medium used to support the growth of fastidious microorganisms? a) chocolate agar b) glucose salts agar c) blood agar d) nutrient agar e) macconkey agar

a) chocolate agar c) blood agar

Ingredients that could be in complex media but not chemically defined media include which of the following? a) extracts of animals, plants, or yeasts b) cell secretions c) disodium hydrogen phosphate d) sodium chloride e) blood and serum

a) extracts of animals, plants, or yeasts b) cell secretions e) blood and serum

Which of the following are true regarding freezing? a) freezing is a good method for preserving foods for long-term storage b) freezing is an effective means of destroying microbes c) freezing is a common method used to preserve stock cultures d) freezing prevents all microbial growth

a) freezing is a good method for preserving foods for long-term storage c) freezing is a common method used to preserve stock cultures

From which environment would you most likely observe growth of psychrophilic microorganisms? a) frozen foods b) frozen foods and water from a hot tub c) water from a hot tub

a) frozen foods

Which of the following are examples of chemotrophs? a) fungi b) photosynthetic bacteria c) mammalian cells d) bacterial pathogens of humans e) algae

a) fungi c) mammalian cells d) bacterial pathogens of humans

Which of the following describe a Petri dish? a) it excludes airborne contaminants b) it is an airtight container that maintains culture purity c) it is a two part covered container made of plastic or glass d) a culture medium in a petri dish can be referred to as a plate of that medium (Ex. an agar plate)

a) it excludes airborne contaminants c) it is a two part covered container made of plastic or glass d) a culture medium in a petri dish can be referred to as a plate of that medium (Ex. an agar plate)

Which of the following are considered major elements that make up cell constituents? a) phosphorous b) oxygen c) molybdenum d) copper e) cobalt f) hydrogen g) nitrogen h) carbon

a) phosphorous b) oxygen f) hydrogen g) nitrogen h) carbon

Which environment is more dynamic and complex? a) soil and its surroundings b) a laboratory environment

a) soil and its surroundings

Environmental factors that influence microbial growth include a) temperature b) pH c) oxygen availability d) water availability e) humidity

a) temperature b) pH c) oxygen availability d) water availability

Which of the following apply to BOTH the spread plate and pour plate methods of counting viable cells? a) the concentration of colony forming units (CFUs) is the original sample can be determined b) plates are incubated, and then the number of colonies is counted c) samples are transferred onto a plate of solid agar and spread over the surface d) a serial dilution of the original sample is performed e) samples are overlaid with melted agar cooled to 50 degrees C and swirled gently to mix

a) the concentration of colony forming units (CFUs) is the original sample can be determined b) plates are incubated, and then the number of colonies is counted d) a serial dilution of the original sample is performed

Which describes the various media that can be prepared for bacterial growth? a) they are diverse in nutrient content and consistency b) they are all similar with respect to their nutrient content c) there are a few different types

a) they are diverse in nutrient content and consistency

Which of the following correctly described facultative anaerobes?a) they can grow without O2 b) their growth is faster when O2 is available c) they can only grow in the absence of O2 d) they can grow in the presence of O2 but do not use it to harvest energy e) they grow better if O2 is present

a) they can grow without O2 b) their growth is faster when O2 is available e) they grow better if O2 is present

Why are species of Staphylococcus halotolerant? a) they have evolved to survive in dry, salty environments such as human skin b) they require high levels of salt in order to survive c) they live in high salt environments, like the salt flats of Utah and the Dead Sea

a) they have evolved to survive in dry, salty environments such as human skin

What term is used to describe the cloudiness of a broth culture? a) turbidity b) clarity factor c) cloud point d) clarity point

a) turbidity

A batch culture has which of the following characteristics? a) wastes are not removed b) it is a closed system c) it is an open system d) it typically involves growth of bacteria or archaea either on agar plates or in tubes or flasks of broths e) nutrients are not renewed f) cells are maintained in a state of continuous growth

a) wastes are not removed b) it is a closed system d) it typically involves growth of bacteria or archaea either on agar plates or in tubes or flasks of broths e) nutrients are not renewed

An ___ is an organism that prefers acidic pH (pH below 7)

acidophiles

A microbe that doesn't use O2 but can grow in environments containing O2 is described as a ___ anaerobe

aerotolerant

The following are steps involved in obtaining a pure culture using the streak-plate method. Place them in the correct order starting from the top. a) the inoculating loop is drawn several times across the surface of a sterile agar plate b) a sterile inoculating loop is dipped into a microbe-containing sample c) the loop is sterilized, and a new series of parallel streaks is made across and at an angle to the original ones d) the petri dish is incubated; distinct, well-isolated colonies form from cells that were separated sufficiently e) the loop is sterilized, and a final set of parallel streaks is made, dragging into the area some organisms from the previous section

b) a sterile inoculating loop is dipped into a microbe-containing sample a) the inoculating loop is drawn several times across the surface of a sterile agar plate c) the loop is sterilized, and a new series of parallel streaks is made across and at an angle to the original ones e) the loop is sterilized, and a final set of parallel streaks is made, dragging into the area some organisms from the previous section d) the petri dish is incubated; distinct, well-isolated colonies form from cells that were separated sufficiently

The procedure shown demonstrates use of good ___ technique and the ___ methoda) sterile; solitary-plate b) aseptic; streak plate c) septic; spread-plate

b) aseptic; streak plate

Which of the following descriptions of biofilms are true? a) biofilms are involved in a small percentage of bacterial infections b) biofims are able to enhance many bioremediation efforts c) bacteria in biofilms can be hundreds of times more resistant to disinfectants than their free-living counterparts d) biofilms are involved in dental plaque, which can lead to tooth decay and gum disease e) biofilms are important in wastewater treatment facilities

b) biofims are able to enhance many bioremediation efforts c) bacteria in biofilms can be hundreds of times more resistant to disinfectants than their free-living counterparts d) biofilms are involved in dental plaque, which can lead to tooth decay and gum disease e) biofilms are important in wastewater treatment facilities

Which term describes organisms which acquire their energy from chemical compounds? a) phototrophs b) chemotrophs c) autotrophs

b) chemotrophs

Complex media contain at least one ingredient that is not chemically defined, such as which of the following? a) tryptophan b) meat extracts c) blood and serum d) extracts of animals, plants, or yeasts e) sodium chloride

b) meat extracts c) blood and serum d) extracts of animals, plants, or yeasts

Which term is used to describe organisms that can obtain energy directly from sunlight? a) saprotrophs b) phototrophs c) chemotrophs

b) phototrophs

During which phase of growth does the number of new cells balance the number of declining cells? a) log phase b) stationary phase c) lag phase d) death phase

b) stationary phase

Imagine you are a microbiologist trying to isolate new species of prokaryotes. You collect numerous samples and return to your lab, where you proceed to encourage any prokaryotes to grow. You are not successful. What is the least likely explanation? a) your atmospheric conditions did not sufficiently match those found in their environment b) there were no prokaryotes present when you sampled c) you did not manage to provide them with all the major elements, trace elements, and growth factors necessary to support their growth d) compounds or conditions that you provided inhibited their growth

b) there were no prokaryotes present when you sampled

Which of the following describe aseptic techniques used in the laboratory? a) they include antimicrobial substances applied to living tissue and skin b) they are used to keep containers, media, and instruments sterile prior to use c) they are important to minimize the chance of contaminating pure cultures

b) they are used to keep containers, media, and instruments sterile prior to use c) they are important to minimize the chance of contaminating pure cultures

The polysaccaride found in marine algae that is commonly used to prepare solid culture media is called a) starch b) peptone c) agar d) gelatin

c) agar

Which of the following best describes how the atmospheric needs of aerobic microbes can be met? a) in a special aerobic chamber b) in a sealed container flushed with a gas like CO2 to remove all the O2 c) by growing them in the air

c) by growing them in the air

In what ways is microbial growth in a colony the same as growth in a liquid? a) cells in both situations experience the same levels of nutrients b) cells in either situation are all in the same phase of growth at the same time c) in both cases, cells compete with one another for available nutrients d) both involve a lag phase followed by exponential growth

c) in both cases, cells compete with one another for available nutrients d) both involve a lag phase followed by exponential growth

In which phase of the growth curve is the generation time measured? a) stationary b) death c) log d) lag

c) log

Put the stages of binary fission in the correct order. a) DNA is moved to each future daughter cell, and a cross wall forms b) the cells separate to yield two daughter cells c) the cell gets longer and DNA is replicated d) the cell divides into two cells

c) the cell gets longer and DNA is replicated a) DNA is moved to each future daughter cell, and a cross wall forms d) the cell divides into two cells b) the cells separate to yield two daughter cells

Optimum environment for psychrophile

cold Arctic regions

Optimum environment for thermophile

compost heap

Consider the following scenario. Unwanted algal blooms in a small lake in Seattle were cleared up by removing excess phosphate from the water. This restricted algal growth. This tells you what about phosphate in this lake? a) phosphate stimulates growth of algae b) phosphate is a trace element c) phosphate is an important source of carbon for algae d) phosphate is the limiting nutrient

d) phosphate is the limiting nutrient.

Which of the following is not a good example of a chemoorganoheterotroph? a) fungi b) humans c) E. coli bacteria d) plants

d) plants