Micro Part 2

Front 1

Question: When you place genes from other organisms into the bacterial chromosome and produce useful products, this is called _______________.
A. bioinformatics B. genomics C. microbial systematics D. biotechnology

Back 1

D. biotechnology

Front 2

True or False. The genomics era brought us into the second golden age of microbiology.
A. true B. false

Back 2

A. true

Front 3

Louis Pasteur contributed what four things to science?

Back 3

1) disproved spontaneous generation
2) Discovered that living organisms discriminate between optical isomers
§ Discovered that alcoholic fermentation was a biologically mediated process
§ Developed vaccines for anthrax, fowl cholera, and rabies

Front 4

Robert Koch contributed what to science?

Back 4

Demonstrated the link between microbes and infectious
diseases
§ Identified causative agents of anthrax and tuberculosis
§ Koch’s postulates (Figure 1.15) § Developed techniques (solid media) for obtaining pure
cultures of microbes, some still in existence today

Front 5

Koch 4 postulates are?

Back 5

1) the suspended pathogenic organism should be present in all cases of the disease and absent from healthy animals
2) The suspended organism should be grown in pure culture
3) Cells from a pure culture should cause disease in a healthy animal
4) The organism should be reisolated and show to be the same as the original

Front 6

is Koch’s Postulates still relevant today?

Back 6

yes it is still the "gold stardard" for medical microbiology (though it doesn't work for every infectious disease); his postulates can be easily proved

Front 7

Question: The evolutionary relationship between two organisms is their _______________.
A. kinship B. phylogeny C. family history D. chronology

Back 7

B. phylogeny

Front 8

Question: How can you distinguish a phototroph from a chemotroph in the microscope?
A. chemotrophswillbelarger B. phototrophswillhavecolor C. phototrophs will have more energy D. chemotrophs won’t stain

Back 8

B. phototrophswillhavecolor

Front 9

Light microscopes: relatively ____ magnification; Limit of resolution for light microscope is about ______.

Back 9

low; 0.2 μm

Front 10

Resolution definition

Back 10

he ability to distinguish two adjacent objects
as separate and distinct

Front 11

How to prepare stains for microbiobial inspection

Back 11

1) spread culture over slide
2) air dry
3) heat fix
4)Flood slide with stain; rinse and dry

Front 12

Differential Stains are?

Back 12

Gram stain

Front 13

Gram-positive bacteria appear ______ and gram-negative bacteria appear _____ after staining

Back 13

purple; red

Front 14

What is Widely used in microbial ecology for enumerating bacteria in natural samples

Back 14

Fluorescence Microscopy
§ Used to visualize specimens that fluoresce

Front 15

Electron Microscopy uses ____ instead of _______ to image cells and structure and the two types of electron microscopes are?

Back 15

electrons; photons; Two types of electron microscopes § Transmission Electron Microscopes (TEM) § Scanning Electron Microscopes (SEM)

Front 16

Question: What color are gram-negative bacteria after doing the Gram stain?
A. blue B. red C. green D. purple

Back 16

B. red

Front 17

what do all microbial cells have the following in common?

Back 17

Cytoplasmic membrane
§ Cytoplasm § Ribosomes

Front 18

what's the difference betw. Eukaryotes and Prokaryotes?

Back 18

Prokaryotes: no membrane bound organelles, no nucleus, generally smaller than eukaryotes
Eukaryotes: DNA encloused in membrane bound nucleus; contain organelles and generally more complex and larger

Front 19

Viruses are ___ considered cells, they have no ____ abilities of their own and they Rely completely on ________ ________ ______ ______ _____
Infect ___ types of cells

Back 19

not; metabolic; biosynthetic machinery of infected cells; all

Front 20

Genome is?

Back 20

A cell’s full complement of genes

Front 21

Prokaryotic DNA are?

Back 21

circular (= chromosome)
§ Prokaryotes also may have small amounts of extra- chromosomal DNA called plasmids that confer special properties ( i.e. antibiotic resistance)

Front 22

Eukaryotic DNA is?

Back 22

linear and found within the nucleus
§ Associated with proteins that help in folding of the DNA § Usually have more than one chromosome § Typically have two copies of each chromosome

Front 23

Escherichia coli Genome has _______ million base pairs

Back 23

4.68

Front 24

Human Genome _______ more DNA per cell than E. coli

Back 24

1,000x

Front 25

Evolution

Back 25

Change in a line of descent § Results in new varieties and species of organisms

Front 26

Phylogeny

Back 26

Evolutionary relationships between organisms
§ Relationships can be deduced by comparing genetic information (nucleic acid or amino acid sequences)

Front 27

__________ are excellent molecules for determining phylogeny

Back 27

rRNA

Front 28

Ribosomal RNA (rRNA) Gene Sequencing and Phylogeny steps?

Back 28

1) isolate DNA 2) PCR 3) sequence anaylsis 4) make tree

Front 29

Comparative rRNA sequencing has defined three distinct lineages of cells called ______.

Back 29

domains; bacteria, Archaea. Eukarya

Front 30

§ Archaea and Bacteria are ____ closely related.
______ are more closely related to Eukarya than Bacteria.

Back 30

NOT; archaea

Front 31

Mitochondria and chloroplasts took up residence in Eukarya eons ago
§ This arrangement is known as _________

Back 31

endosymbiosis

Front 32

Mitochondria and chloroplasts also contain their own _____ and _______

Back 32

genomes; ribosomes

Front 33

Chemoorganotrophs

Back 33

Obtain their energy from the oxidation of organic
molecules

Front 34

Chemolithotrophs

Back 34

Obtain their energy from the oxidation or inorganic
molecules § Process found only in prokaryotes

Front 35

Phototrophs

Back 35

Contain pigments that allow them to use light as an
energy source § Oxygenic photosynthesis produces oxygen § Anoxygenic photosynthesis does not produce oxygen

Front 36

All cells require ______ as a major nutrient

Back 36

carbon

Front 37

Autotrophs

Back 37

§ Use carbon dioxide as their carbon source § Sometimes referred to as primary producers

Front 38

Heterotrophs

Back 38

§ Require one or more organic molecules for their carbon
source
§ Feed directly on autotrophs or live off products produced by autotrophs

Front 39

Organisms that inhabit extreme environments are called __________.

Back 39

extremophiles; Habitats include boiling hot springs, glaciers, extremely salty bodies of water, and high pH environments

Front 40

Hyperthermphile

Back 40

high temperture;

Front 41

psychrophile

Back 41

low temperature

Front 42

acidophile

Back 42

pH low

Front 43

Alkalphile

Back 43

high pH

Front 44

barophile

Back 44

pressure

Front 45

halophile

Back 45

salt

Front 46

The _______ make up the largest division of Bacteria.
- Gram-_______

Back 46

proteobacteria; postition

Front 47

_____ are relatives of gram-_______ bacteria
§ ________ to the evolution of life

Back 47

cyanobacteria; negative and are _______

Front 48

Green sulfur bacteria and green nonsulfur bacteria are
___________

Back 48

photosynthetic

Front 49

Deinococcus?

Back 49

are extremely resistant to radioactivity

Front 50

Chlamydia

Back 50

are obligate intracelluar parasites

Front 51

Methanogens:

Back 51

anaerobically degrade organic matter,
produce methane (natural gas)

Front 52

Extreme halophiles:

Back 52

require high salt concentrations for metabolism and reproduction

Front 53

Thermoacidophiles:

Back 53

grow in moderately high temperatures and low pH environments

Front 54

Crenarchaeota

Back 54

Vast majority of cultured Crenarchaeota are
hyperthermophiles § Some live in marine, freshwater, and soil systems

Front 55

3 Euryarchaeota are?

Back 55

Methanogens;Extreme halophiles;Thermoacidophiles

Front 56

Eukaryotic microorganisms are collectively known as _______.

Back 56

protists

Front 57

Algae and fungi have __________ whereas protozoa do not

Back 57

cell walls

Front 58

_______ are an example of a mutualistic relationship between two groups of protists
§ Fungi and cyanobacteria § Fungi and algae

Back 58

lichens

Front 59

Major chemical elements in organisms:

Back 59

S, P, O, H, N, C
Support for People with Oral and Head and Neck Cancer

Front 60

Covalent bond:

Back 60

strong bond between chemical elements Electrons are shared equally between atoms

Front 61

Molecule:

Back 61

two or more chemically bonded atoms

Front 62

True or False. Without microbes humans would not exist.
A. true B. false

Back 62

Answer: A. true. The simplest explanation is the universal ancestor was a microorganism. All life evolved from that ancestral cell; therefore, without microbes we wouldn’t exist. Also, take note that oxygen would not have formed on earth without microbes and we require oxygen to breath. There are countless examples the importance of microbes to humans.

Front 63

True or False. Microorganisms can change the characteristics of their habitat.
A. true B. False

Back 63

Answer: A. true. For example, microbes that colonize the teeth and fo plaque can ferment sucrose and produce lactic acid, which lowers the p of the mouth; therefore, changing the habitat.

Front 64

Question: When you place genes from other organisms into the bacterial chromosome and produce useful products, this is called _______________.
A. bioinformatics B. genomics C. microbial systematics D. Biotechnology

Back 64

Answer: D. biotechnology

Front 65

True or False. The genomics era brought us into the second golden age of microbiology.
A. true B. False

Back 65

Answer: A. true
§ The sequencing of genomes began in the 1990s. The first genomes sequenced were those of microorganisms. When these genomes were studied a number of discoveries were made, which stimulated much interest in microbes.

Front 66

Question: The evolutionary relationship between two organisms is their _______________. A. kinship B. phylogeny
C. family history D. chronology

Back 66

B. phylogeny

Front 67

Question: How can you distinguish a phototroph from a chemotroph in the microscope? A. chemotrophswillbelarger B. phototrophswillhavecolor
C. phototrophs will have more energy D. chemotrophs won’t stain

Back 67

Answer: B. phototrophs will have color

Front 68

Question: What color are gram-negative bacteria after doing the Gram stain? A. blue B. red
C. green D. purple

Back 68

B. red

Front 69

Question: The two strands of DNA are held together by _______________. A. hydrogen bonds B. ionic bonds
C. peptide bonds D. none of the above

Back 69

hydrogen bonds

Front 70

Question: The amino acids of a growing peptide chain are held together by _______________.
A. hydrogen bonds B. ionic bonds C. peptide bonds D. none of the above

Back 70

Answer: C. peptide bonds
§ The amino and carboxylic acid groups of amino acids form a peptide bond.

Front 71

Question: The hydrogen atoms of a water molecule are bonded to the oxygen atom by _______________ bonds, whereas neighboring water molecules are held together by _______________ bonds. A. hydrogen; ionic
B. hydrogen; polar covalent C. polar covalent; hydrogen D. ionic; covalent E. polar covalent; ionic

Back 71

Answer: C. polar covalent; hydrogen
§ Within a single water molecule, the bond is a polar covalent because the electrons are shared but are shared unequally. Because of this, one atom becomes slightly negatively charged and the other slightly positively charged. This results in two water molecules joining by a hydrogen bond where the slight positive charge of one end is attracted by the slight negative charge of the other.

Front 72

Question: What three things make up nucleotides?
A. sugar, phosphate, nitrogenous base B. acid, phosphate, sugar C. nitrogenous base, sugar, acid D. phosphate, nitrogenous base, acid

Back 72

Answer: A. sugar, phosphate, nitrogenous base
§ The sugar is ribose in RNA or deoxyribose in DNA. Phosphate exists in both RNA and DNA. The nitrogenous bases are A,U, C, or G in RNA or A,T, C, or G in DNA.

Front 73

Question: What four groups make up an amino acid?
A. amino, variable (R), hydroxyl, hydrogen B. amino, variable (R), ester, hydrogen C. amino, variable (R), carboxylic acid, hydrogen D. amino, variable (R), carboxylic acid, ether

Back 73

Answer: C. amino, variable (R), carboxylic acid, hydrogen
§ The amino and carboxylic groups make up the peptide. Each amino acid also has a variable group, specific for each amino acid, and a hydrogen group.

Front 74

Question: A peptide bond is formed when _______________.
A. two amino acids join together and water is released B. two amino acids join together and water is added C. two amino acids are separated and water is released D. two amino acids are separated and water is added

Back 74

§ Answer: A. two amino acids join together and water is released
§ When a peptide bond joins two amino acids together, the –OH from the hydroxyl group and a hydrogen from the amino group bond together, resulting in the release of water.

Front 75

Question: Carbohydrates have carbon, hydrogen, and oxygen in a ratio of _______________.
A. 1:3:1 B. 1:2:1 C. 2:1:1 D. 1:1:2

Back 75

Answer: B. 1:2:1 § C6H12O6 (glucose) is an example. 6:12:6 is the same ratio as 1:2:1.

Front 76

Question: The bond that holds carbohydrates together is called a _______________. A. hydrogen bond B. peptide bond
C. phosphodiester bond D. glycosidic bond

Back 76

Answer: D. glycosidic bond
§ Two OH groups combine so that there is the release of one molecule of water and then the remaining oxygen atom links the two sugar molecules together in a glycosidic bond.

Front 77

Question: A hydroxyl group is _______________.
A. –OH B. –NH2 C. –CH3 D. –COOH

Back 77

Answer: A. –OH
-NH2 is an amino group. CH3 is a methyl group and COOH is a carboxylic acid group.

Front 78

True or False. A population of spherical cells with a diameter of 1 μm will persist better in a nutrient- limiting environment than a population of spherical cells with a diameter of 5 μm.
A. true B. False

Back 78

Answer: A. true
§ A smaller diameter means a smaller radius, which results in a larger surface area to volume ratio. A larger SA/V ratio allows smaller cells to support a greater nutrient exchange per unit volume.

Front 79

Question: If you had a cell with the structures listed below, what would be the outermost layer of this hypothetical cell?
A. peptidoglycan B. LPS C. slime layer D. cytoplasmic membrane

Back 79

Answer: C. slime layer From the inside to the outside of a gram-negative cell you would find the cytoplasmic membrane, peptidoglycan, LPS, and slime layer.

Front 80

Question: Approximately what percentage of the gram-positive cell wall is composed of peptidoglycan?
A. 10% B. 50% C. 90% D. 100%

Back 80

Answer: C. 90% Gram-negative cell walls have approximately 10% peptidoglycan.

Front 81

Question: What aspects of the peptidoglycan are responsible for its strength?
A. the beta 1,4-glycosidic bonds and the techoic acids
B. thebeta1,4-glycosidicbondsandthecrosslinksthat connect the chains of peptidoglycan
C. the peptide bonds in the tetrapeptide side chains and the techoic acids
D. the ester linked phospholipids

Back 81

Answer: B. the beta 1,4-glycosidic bonds and the cross links that connect the chains of peptidoglycan

Front 82

Question: What portion of the gram-negative cell wall is toxic?
A. peptidoglycan B. O-polysaccharide C. phospholipid D. lipidA

Back 82

Answer: D. lipid A Lipid A is an endotoxin that is released by gram-negative cells when they lyse open. This toxin can cause shock and fever in some hosts.

Front 83

Question: A slime layer or capsule helps a cell to _______________.
A. prevent osmotic lysis B. transportnutrients C. disperse in a liquid environment D. make a biofilm

Back 83

Answer: D. make a biofilm A biofilm is a polysaccharide matrix containing microbial cells. Cells typically secrete a polysaccharide layer (slime layer) during biofilm formation.

Front 84

Question: Sporulation in endospore-forming bacteria occurs when _______________.
A. a key nutrient used by the organism becomes depleted
B. theorganismexperienceselevatedtemperature
C. the organism is exposed to antibiotics
D. the environment surrounding the organism becomes very moist

Back 84

Answer: A. a key nutrient used by the organism becomes depleted A vegetative cell produces an endospore when a nutrient becomes depleted. Spore germination can occur if the endospore experiences elevated (but not lethal) temperatures.

Front 85

Question: Which portion of the flagella is responsible for changing the direction of its rotation?
A. mot proteins B. l-ring C. flagellin D. fli proteins

Back 85

Answer: D. fli proteins They act as the switch that changes the rotation of the flagella.

Front 86

Question: What happens when a motile cell with a chemotactic response senses a higher concentration of an attractant?
A. its flagella spin faster B. thetumblesbecomelessfrequent C. the flagella switch the direction of rotation D. the tumbles become more frequent

Back 86

Answer: B. the tumbles become less frequent. The runs occur longer.

Front 87

Question: Which of the following uses gliding motility?
A. Escherichia coli B. Cyanobacteria C. Rhodospirillum D. Pseudomonas

Back 87

Answer: B. Cyanobacteria E. coli has peritrichous flagella, Pseudomonas uses twitching motility and Rhodospirillum has a polar flagella.

Front 88

Question: Which structure confers buoyancy on a cell and allows it to float up and down in a water column?
A. flagella B. magnetosome C. polyphosphate D. gas vesicle

Back 88

Answer: D. gas vesicle Flagella are used for motility and chemotaxis. Magnetosomes allow cells to respond to magnetic fields. Polyphosphate allows cells to store phosphate.

Front 89

Question: Which of the following macronutrients makes up both amino acids and nucleotides?
A. nitrogen B. phosphorous C. iron D. potassium

Back 89

§ Answer: A. nitrogen
§ Nitrogen is found in the amino group of amino acids and some of the variable group side chains. It is also found in the nitrogenous bases in nucleotides. Phosphorous is found in nucleotides but not amino acids. Iron and potassium are not found in either amino acids or nuceotides.

Front 90

Question: Which of the following is considered a growth factor? A. iron B. vitamins
C. hydroxamic Acid D. potassium

Back 90

§ Answer: B. vitamins
§ Iron, hydroxamic acid, and potassium are all trace metals. Vitamins are the only growth factors.

Front 91

Question: In which type of media would an investigator add specific factors or nutrients that would allow certain organisms to grow that would not normally grow?
A. chemicallydefined B. differential C. selective D. enrichment

Back 91

§ Answer: D. enrichment
§ Certain bacteria require enrichment media that contains a complex defined medium with additional nutrients added that allow certain bacteria to grow.

Front 92

Question: Which type of media allows the bacteria to become visible and form colonies? A. liquid culture B. solid culture C. chemically defined media D. chemically complex media

Back 92

§ Answer: B. solid culture
§ When bacteria are grown on a solid culture, they are grown on a petri dish with hardened media. The colonies become visible on top of this media.

Front 93

Question: If ΔG0' < 0, then _______________.
A. B. C. D.
the reaction is exergonic and can occur spontaneously the reaction is endergonic and can occur spontaneously the reaction is exergonic and cannot occur spontaneously the reaction is endergonic and cannot occur spontaneously

Back 93

§ Answer: C. the reaction is exergonic and can occur spontaneously
§ By definition, if ΔG0' < 0, the reaction is exergonic. A reaction that is exergonic does not require an input of energy and can occur spontaneously.

Front 94

Question: Which of the following are characteristics of enzymes?
A. they are consumed by the enzyme-mediated reaction B. they are not altered by the enzyme-mediated reaction C. they raise activation energy D. all of the above

Back 94

§ Answer: B. they are not altered by the enzyme-mediated reaction § Enzymes can be used again in other reactions because they are not altered.
Enzymes also lower the activation energy.

Front 95

Question: Which of the following terms relate to enzymes?
A. proteins B. active site C. catalysts D. all of the above

Back 95

§ Answers: D. all of the above
§ Enzymes are under the class of molecules known as proteins. The substrate binds to the enzyme at the active site. Enzymes speed up the rate of a reaction without being altered so they are also classified as catalysts.

Front 96

Question: Which of the following macronutrients makes up both amino acids and nucleotides?
A. nitrogen B. phosphorous C. iron D. potassium

Back 96

§ Answer: A. nitrogen
§ Nitrogen is found in the amino group of amino acids and some of the variable group side chains. It is also found in the nitrogenous bases in nucleotides. Phosphorous is found in nucleotides but not amino acids. Iron and potassium are not found in either amino acids or nuceotides.

Front 97

Question: Which of the following is considered a growth factor? A. iron B. vitamins
C. hydroxamic Acid D. potassium

Back 97

Answer: B. vitamins Iron, hydroxamic acid, and potassium are all trace metals. Vitamins are the only growth factors.

Front 98

Question: In which type of media would an investigator add specific factors or nutrients that would allow certain organisms to grow that would not normally grow?
A. chemicallydefined B. differential C. selective D. enrichment

Back 98

§ Answer: D. enrichment
§ Certain bacteria require enrichment media that contains a complex defined medium with additional nutrients added that allow certain bacteria to grow.

Front 99

Question: Which type of media allows the bacteria to become visible and form colonies? A. liquid culture B. solid culture C. chemically defined media
D. chemically complex media

Back 99

§ Answer: B. solid culture
§ When bacteria are grown on a solid culture, they are grown on a petri dish with hardened media. The colonies become visible on top of this media.

Front 100

Question: If ΔG0' < 0, then _______________.
A. B. C. D.
the reaction is exergonic and can occur spontaneously the reaction is endergonic and can occur spontaneously the reaction is exergonic and cannot occur spontaneously the reaction is endergonic and cannot occur spontaneously

Back 100

§ Answer: C. the reaction is exergonic and can occur spontaneously
§ By definition, if ΔG0' < 0, the reaction is exergonic. A reaction that is exergonic does not require an input of energy and can occur spontaneously.

Front 101

Question: Which of the following are characteristics of enzymes?
A. they are consumed by the enzyme-mediated reaction B. they are not altered by the enzyme-mediated reaction C. they raise activation energy D. all of the above

Back 101

§ Answer: B. they are not altered by the enzyme-mediated reaction § Enzymes can be used again in other reactions because they are not altered.
Enzymes also lower the activation energy.

Front 102

Question: Which of the following terms relate to enzymes?
A. proteins B. active site
C. catalysts D. all of the above

Back 102

§ Answers: D. all of the above
§ Enzymes are under the class of molecules known as proteins. The substrate binds to the enzyme at the active site. Enzymes speed up the rate of a reaction without being altered so they are also classified as catalysts.

Front 103

Question: Which of the following molecules could serve as an electron donor in the electron transport chain?
A. FAD+ B. NADH C. NAD+ D. NADPH

Back 103

§ Answer: B. NADH
§ Both NADH and NADPH could serve as electron donors but NADPH is involved with photosynthesis. NAD+ and NADP+ could serve as electron acceptors.

Front 104

True or False. During lag phase cells are not very metabolically active. A. true B. false

Back 104

§ Answer: B. false
§ During lag phase the cells are very metabolically active. They are actively creating monomers and macromolecules and creating energy to gear up for log phase.

Front 105

Question: If you wanted to increase the growth yield of a continuous culture you would _______________. A. increase the concentration of the nutrients in the culture B. increase the dilution rate of the continuous culture
(flow rate of media)
C. decrease the concentration of the nutrients in the culture
D. decrease the dilution rate of the continuous culture (flow rate of media)

Back 105

§ Answer: A. increase the concentration of nutrients in the culture
§ With cells in steady state in a chemostat, if the nutrient concentration is increased in the system and the dilution rate is kept constant, the growth yield (concentration of cells/ml) is increased in the system.

Front 106

True or False. A culture in a test tube is an example of a batch culture. A. true B. false

Back 106

Answer: A. true
Batch cultures are closed systems (no input of fresh nutrients or loss of waste).

Front 107

Question: When a culture is incubated at a temperature that is above the organism’s maximum temperature for growth, what happens?
A. the transport of nutrients into the cell is slow; therefore the cells grow more slowly than normal
B. the cells grow much faster than normal because the enzymatic reactions are occurring at a much faster rate.
C. thecellmembranescollapseandproteins denatureand the cell usually dies
D. the cell continues to grow at the normal rate

Back 107

§ Answer: C. the cell membranes collapse and proteins denature and the cell usually dies
§ At temperatures below the optimum the transport of nutrients into the cells is slow; therefore the cells grow more slowly than normal. The cells grow at their fastest rate when they are at their optimal temperature for growth.

Front 108

Question: What is the optimum temperature for a thermophile? A. above 80 degrees C B. 45 to 80 degrees C
C. 20 to 40 degrees C D. below 40 degrees C

Back 108

§ Answer: B. 45 to 80 degrees C § Hyperthermophiles have optimum temperatures above 80 degrees.

Front 109

Question: If you have 100 cells at 1:00 p.m. and these cells have a generation time of 30 minutes, how many cells do you have at 5:00 p.m. (assuming the cells are growing exponentially)?
A. 400 cells B. 800 cells C. 1,600 cells D. 25,600 cells

Back 109

§ Answer: D. 25,600 cells § No=100, N=?, n=?, g=30 minutes, and t=240 minutes § n=t/g=240min/30min per generation
§ n=8 generations § N=No(2n)=100 cells x 28=25,600 cells

Front 110

Question: A _______________ is used to estimate culture concentration by measuring turbidity.
A. pour plate method B. viable count
C. spectrophotometer D. microscope

Back 110

§ Answer: C. spectrophotometer
§ This measures percent transmittance of light at a specific wavelength passing through the culture. %T can be converted to optical density, which can be used to estimate culture concentration.

Front 111

Question: Consider a chemostat. If you were to increase the dilution rate slightly, what would happen? (Assume the chemostat is in steady state.)
A. B.
C. D.
bacterial concentration or growth yield would increase in the chemostat
doubling time of the culture in the chemostat would decrease
growth yield would increase while doubling time would decrease in the chemostat
growth yield and doubling time would increase in the chemostat

Back 111

§ Answer: B. doubling time of the culture in the chemostat would decrease
§ During steady state increasing the dilution rate increases the growth rate (decreases the doubling time). You can continue to increase the growth rate until washout occurs. This is when the dilution rate is faster than the fastest doubling time for the culture under the conditions provided.

Front 112

Question: If you placed a mesophile at 20 degrees C, what would happen? A. it would die B. it would grow optimally
C. it would grow less than optimally D. it would lyse open

Back 112

§ Answer: C. it would grow less than optimally
§ The optimal temperature of a mesophile is around 39 degrees C. At 20 degrees C the membrane becomes more rigid and enzymatic reactions occur more slowly; therefore, the cell would grow more slowly.

Front 113

Question: An organism that grows at a pH of 9 is a(n) _______________
A. acidophile B. thermophile C. alkaliphile D. osmophile

Back 113

Answer: C. alkaliphile

Front 114

Question: Which of the following organisms have a particularly difficult time maintaining a proton motive force? A. psychrophiles
B. acidophiles C. osmophiles D. alkaliphiles

Back 114

§ Answer: D. alkaliphiles
§ When protons are shuttled across the cytoplasmic membrane during electron transport the protons will be neutralized by the alkaline environment; therefore it would be difficult to set up a gradient of protons (PMF).

Front 115

True or False. Obligate anaerobes require the enzyme catalase to detoxify byproducts of metabolism. A. true
B. false

Back 115

§ Answer: B. false
§ Catalase is used to detoxify byproducts of metabolic reactions involving oxygen. Obligate anaerobes do not use oxygen in their metabolism; therefore they wouldn’t need this enzyme.

Front 116

Question: When do batch cultures enter stationary phase? A. when the temperature of the culture changes B. when the culture is transferred to fresh media
C. when the nutrient concentration in the media is diminished D. all of the above

Back 116

§ Answer: C. when the nutrient concentration in the media is diminished
§ Two things affect when cells enter stationary phase: (1) depletion of a nutrient and (2) build up of waste.

Front 117

Question: Which of the following is true about death phase?
A. absolutely no new cells form during this phase B. the number of dying cells is greater than the number of
new cells
C. all new cells that form during this phase immediately die
D. the number of new cells is equal to the number of dying cells

Back 117

§ Answer: B. the number of dying cells is greater than the number of new cells
§ Death phase occurs when the NET number of cells stays approximately the same. Some new cells are still forming, but more cells are dying.

Front 118

Question: Lucy diluted a sample to a factor of 10-4 (or 1/104) and did a spread plate of 1 ml of the diluted culture. The next day she counted 87 colonies on the plate. What was the concentration of the original sample? A. 8.7 X 103 cfu/ml sample B. 8.7 X 104 cfu/ml sample C. 8.7 X 105 cfu/ml sample D. 8.7 X 106 cfu/ml sample

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§ Answer: C. 8.7 X 105 cfu/ml sample
§ Each colony on the plate is considered a colony forming unit in the original culture. We had 87 cfu’s in this example. If you divide that number by the volume plated, then divide that number by the dilution factor, you get 8.7 X 105 cfu/ml sample.

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Question: Before an indirect method, such as turbidity readings, can be used to measure cell concentration a _______________ has to be prepared.
A. standard curve B. growth curve C. standard culture D. fermentation balance

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§ Answer: A. standard curve § You would need to do a direct count method (plate count or direct microscopic count) for a
culture. Then you would create a graph comparing the direct count to optical density taken at various dilution levels.