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53 Cards in this Set
- Front
- Back
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If cells are grown in media containing amino acids labeled with radioactive nitrogen (15N), most of radioactivity will be found in the cells' __________.
a) DNA b) proteins c) phospholipids d) DNA and proteins e) DNA and phospholipids |
d) DNA and proteins |
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Which of the following elements is NOT correctly matched with its cellular function?
a) nitrogen - needed for amino acid synthesis b) sulfur - used for synthesis of thiamin and biotin c) phosphorus - incorporated into nucleic acids d) magnesium and potassium - required as cofactors for enzymes e) none of the answers is correct; all of the elements are correctly matched |
e) none of the answers is correct; all of the elements are correctly matched |
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Pathogenic bacteria isolated from the respiratory or intestinal tract of humans are _________.
a) strict aerobes that grow best in candle jars b) capnophiles that prefer highly oxygenated growth conditions c) capnophiles that grow best in carbon dioxide incubators d) strict aerobes that grow best in reducing media e) facultative anaerobes that require reducing media for growth |
c) capnophiles that grow best in carbon dioxide incubators |
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The biosafety level (BSL) for most introductory microbiology laboratories is ________.
a) BSL - 1 b) BSL - 2 c) BSL - 3 d) BSL - 4 |
a) BSL - 1 |
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The biosafety level (BS) for a clinical microbiology working with potentially airborne pathogens, such as tuberculosis bacteria, is _________.
a) BSL - 1 b) BSL - 2 c) BSL - 3 d) BSL - 4 |
c) BSL - 3 |
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A sample of milk is tested for its bacterial content in a plate count assay. A one-milliliter sample of the milk is diluted in a 1:10 dilution series. One milliliter of the third dilution tube is plated in a pour plate. After incubation, the plate has 54 colonies, indicating that the original milk sample contained _________.
a) 54 cells b) 540 cells c) 5400 cells d) 54,000 cells e) 540,000 cells |
d) 54,000 cells |
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The addition of which of the following to a culture medium with neutralize acids?
a) sugars b) carbon c) heat d) buffers e) pH |
d) buffers |
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Salts and sugars work to preserve foods by creating a ____________.
a) hypertonic environment b) depletion of nutrition c) hypotonic environment d) lower osmotic pressure e) lower pH |
c) hypotonic environment |
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The term aerotolerant anaerobe refers to an organism that _________.
a) requires more oxygen than is present in air b) is killed by oxygen c) does not use oxygen but tolerates it d) uses oxygen or grows without oxygen e) requires less oxygen than is present in air |
c) does not use oxygen but tolerates it |
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Which of the following is an advantage of the standard plate count?
a) can readily count cells that form aggregates b) can be performed on very dilute samples, such as lake water c) provides immediate results d) can be used to count heat-sensitive bacteria e) determines the number of viable cells |
e) determines the number of viable cells |
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Which of the following is an advantage of the direct microscope count?
a) requires no incubation time b) can readily count organisms that are motile c) sample volume is unknown d) can easily distinguish live from dead cells e) requires a large number of cells |
a) requires no incubation time |
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Most bacteria reproduce by _________.
a) aerial hyphae b) binary fission c) mitosis d) fragmentation e) budding |
b) binary fission |
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Thirty-six colonies grew in nutrient agar from 1.0 ml of diluted sample in a standard plate count. How many cells were in the original sample?
a) 4 b) 9 c) 18 d) 36 e) 72 |
d) 36 |
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Most bacteria grow best at pH _______.
a) 1 b) 5 c) 7 d) 9 e) 14 |
c) 7 |
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Most fungi grow best at ph _______.
a) 1 b) 5 c) 7 d) 9 e) 14 |
b) 5 |
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A culture medium on which only gram-positive organisms and a yellow halo surrounds Staphylococcus aureus colonies is called a(n) __________.
a) differential medium b) selective medium c) enrichment culture d) selective and differential medium e) differential and enrichment culture |
d) selective and differential medium |
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A culture medium consisting of agar, peptone, and beef heart is a _________.
a) chemically defined medium b) complex medium c) reducing medium d) selective medium e) differential medium
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b) complex medium |
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Which of the following pairs is mismatched?
a) psychotroph - growth at 0 degrees C b) hyperthermophiles - growth at 85 degrees C c) psychorophile - growth at 15 degrees C d) thermophile - growth at 37 degrees C e) mesophile - growth at 25 degrees C |
d) thermophile - growth at 37 degrees C |
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During which phase will gram-positive be most susceptible to penicillin?
a) log phase b) death phase c) stationary phase d) lag phase e) the culture is equally susceptible during all phases |
a) log phase |
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Which of the following is the best definition of generation time?
a) the length of time needed for lag phase b) the time needed for nuclear division c) the minimum rate of doubling time d) the duration of log phase e) the length of time needed for a cell to divide |
e) the length of time needed for a cell to divide |
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Which of the following is NOT a direct method to measure microbial growth?
a) direct microscopic count b) metabolic activity c) standard plate count d) filtration e) most probable number (MPN) |
b) metabolic activity |
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Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt?
a) facultative halophiles b) thermophiles c) anaerobes d) hyperthermophiles e) psychorophiles |
a) facultative halophiles |
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Which of the following is an organic growth factor?
a) NH4H2PO4 b) peptone c) H2O d) vitamin B1 e) glucose |
d) vitamin B1 |
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Which of the following is an example of a metabolic activity that could be used to measure microbial growth?
a) standard plate count b direct microscopic count c) MPN d) glucose consumption e) turbidity |
d) glucose consumption |
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An experiment began with 4 cells and ended with 128 cells. How many generations did the cells go through?
a) 64 b) 32 c) 6 d) 5 e) 4 |
d) 5 |
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The source of nutrients in nutrient agar is _______.
a) agar b) nutrient c) peptone and beef extract d) peptone and NaCl e) agar and NaCl |
c) peptone and beef extract |
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Which enzyme catalyzes the reaction: O2- + O2- + 2H+ --> H2O2 + O2?
a) oxidase b) peroxidase c) superoxide dimutase d) catalase |
c) superoxidase dimutase |
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Which enzyme catalyzes the reaction: 2H2O2 --> 2H2O + O2?
a) oxidase b) peroxidase c) superoxide dimutase d) catalase |
d) catalase |
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Which enzyme catalyzes the reaction: H2O2 + 2H+ --> 2H2O?
a) oxidase b) catalase c) peroxidase d) superoxide dimutase |
c) peroxidase |
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True or false: An isolated colony on a streak plate contains millions or billions of identical cells. |
true |
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True or false: Bacterial growth refers to an increase in the number of cells in a bacteria culture. |
true |
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True or false: Pure cultures can easily be obtained on streak plates, even if the desired bacteria are present in very low concentrations. |
false |
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True or false: Agar is used as a solidifying agent in microbiological media since few bacteria can degrade it. |
true |
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True or false: Laboratory cultivation of obligate anaerobes requires reducing media or special growth chambers filled with inert gases. |
true |
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True or false: Most pathogenic bacteria are thermophiles. |
false |
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True or false: In performing a ten-fold dilutions series from a sample containing 10,000 bacteria per milliliter, the fourth tube in the dilution series will have 10 cells per milliliter. |
false |
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True or false: Turbidity is an indirect measurement of bacterial growth that can be measured using a spectrophotometer. |
true |
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True or false: Filtration methods are used to count bacteria present in very low concentrations, such as in lakes and streams. |
true |
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True or false: Nitrogen-fixing bacteria, such as cyanobacteria, can use atmospheric nitrogen (N2) for their nitrogen source. |
true |
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What are the steps of binary fission? |
1) cell elongates and DNA is replicated 2) cell wall and plasma begin to constrict 3) cross-wall forms, completely separating the two DNA copies 4) cells separate |
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What is the key Fts protein involved in cell division? |
FtsZ --> filamenting temperature sensitive mutant Z
Fts = filamentous temperature sensitive |
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FtsZ proteins form a ____________. What is this? |
divisome
Divisome defines the division plane, then polymerizes into a ring and attracts more proteins. |
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What are the enzymes that cut and are similar in function to lysosomes? |
autolysins |
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What are the lipid carrier molecules that transport building blocks across the membrane? What are these building blocks? |
bactoprenol carry NAG/NAM/pentapeptide |
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How are building blocks transported by bactoprenol? |
carrier inserts the building block into the glycerin backbone, then moves back inside the cell to pick up another building block |
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Transpeptidation replaces the requirement for _____________. |
energy |
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What are the physical and chemical requirements for growth? |
physical: temperature, pH, osmotic pressure
chemical: carbon, nitrogen, sulfur, phosphorus, trace elements, oxygen, and an organic growth factor |
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What is the danger zone for rapid growth of bacteria which may result in the production of toxins? |
15-55 degrees Celsius |
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Molds and yeasts grow between what pH? |
5 and 6 |
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What are the physical requirements for psychrophily? |
enzymes function optimally in the cold - denatured or inactivated at higher temperatures - more alpha-helix and less beta-sheet - more polar and fewer hydrophobic
active transport occurs at low temperatures
cytoplasmic membranes contain higher concentrations of unsaturated fatty acids |
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What are the physical requirements for thermophily? |
enzymes and other proteins are stable to heat - critical amino acid substitutions - increased number of salt bridges - densely packed highly hydrophobic interiors of proteins
protein synthesizing machinery and structures such as cytoplasmic membrane are also heat stable |
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Hypertonic environments (increase in salt or sugar) causes _____________. |
plasmolysis --> shrinking of a cell's cytoplasm due to water loss |
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What does reducing media consist of? |
chemicals (thioglycolate or oxyrase) that combine O2 |
