Exam 2

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Microbiology
Chapters 5-8, 20
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1

Which microbes grow at an optimum temperature of 15 degrees Celsius?

Psychrophiles

2

Which microbes grow in temperatures between 37 to 65 degrees Celsius?

Thermophiles

3

Which microbes grow in at an optimum temperature range of 20 to 37 degrees Celsius?

Mesophiles

4

What is the maximum temperature for growth of a thermophile?

65 degrees Celsius

5

Which microbe grows in a temperature range of 20 to 45 degrees Celsius?

Mesophiles

6

Which microbe grows in a temperature range of 0 to 20 degrees Celsius?

Psychrophiles

7

At what pH does most bacteria grow?

6.5 to 7.5

8

What is the optimum pH range of acidophiles?

0 to 5.5

9

What is the optimum pH range of basophiles?

8.5 to 11.5

10

How is it that organisms can change the culture media - making it generally more acidic and can be toxic?

Their own waste

11

Which osmotic pressure has no net movement?

Isotonic

12

Which osmotic pressure causes water to move into the cell and possibly cause the cell to burst?

Hypotonic

13

Which osmotic pressure causes water to move out of the cell causing the cell to shrink (plasmolysis)?

Hypertonic

14

What type of microbe grows in high salt conditions?

Halophiles

15

What are the macronutrients?

C-H-O-P-N - carbon, hydrogen, oxygen, phosphate, nitrogen

16

What are trace elements?

Inorganic elements required in small amounts - Fe, Mn, Mg, vitamins (cofactors)

17

Which element is the backbone nutrient?

Carbon

18

What is essential for chemoheterotrophs?

organic carbon sources

19

What is essential for autotrophs and give an example of an autotroph?

CO2; plants

20

Which type of microbes cannot live without oxygen?

Obligate aerobes

21

Which type of microbes can live with or without oxygen?

Facultative anaerobes

22

Which type of microbes cannot live with oxygen?

Obligate anaerobes

23

Which type of microbes tolerate oxygen?

Aerotolerant anaerobes

24

Which type of microbes need less oxygen and more carbon dioxide?

Microaerophiles

25

Complete the equation and name the enzyme to reduce toxicity by removing peroxide (H2O2).

2 H2O2

> 2 H2O +O2; catalase

26

Complete the equation and name the enzyme to reduce toxicity by removing peroxide.

2 H2O2

> 2 H2O + O2; peroxidase

27

Complete the equation and name the enzyme to reduce toxicity by removing superoxide free radicals.

O2- + 2H+

> H2O2 + O2; superoxide dismutase

28

What makes and gets rid of hydrogen peroxide (H2O2)?

Peroxisome

29

Which medium is made of known amounts of chemicals?

synthetic (defined)

30

Which medium is made of some ingredients of unknown composition or amounts?

complex

31

What are some examples of complex mediums?

nutrient broth or tryptic soy broth

32

What is an example of a synthetic medium?

E. coli minimal salts medium

33

What is agar?

complex polysaccharide

34

What is agar used for?

As a solidifying agent for culture media in Petri plates, slants and deeps

35

What makes agar and ideal medium for microbes?

It is generally not metabolized by microbes

36

At what temperature does agar liquefy?

100 degrees Celsius

37

At what temperature does agar solidify?

40 degrees Celsius

38

Which medium encourages the growth of certain organisms while discouraging the growth of others?

Selective medium

39

Which medium distinguishes between different groups of bacteria?

Differential medium

40

Which type of medium contains constituents which cause an observable change (color or pH change)?

Differential medium

41

What is an example of a selective medium?

crystal violet or basic fuschin dyes selective for Gram-

42

Which type of medium provides basic needs?

General medium

43

What is an example of a differential medium?

MacConkey contains lactose and neutral red, lactose fermenters appear pink; blood agar - hemolysis

44

What is the time required for cells to divide (and thus double the population) and can be as short as 20 minutes or longer than a day?

Generation time

45

What are the four phases of the growth curve?

Lag

Log

Stationery

Death

46

Which phase is best for adding anything?

log phase

47

Which phase is when the growth and death of cells is about even?

stationary phase

48

Which phase is when the death of the cells exceeds the growth of the cells?

death phase

49

Which phase is where the bacteria is adjusting to the environment?

lag phase

50

What is the difference in indirect and direct methods of counting bacteria?

In direct, only live bacteria are measured; in indirect living and dead bacteria are counted

51

What is a way to measure metabolic activity?

use glucose

52

Which method of measurement requires the bacteria to be dried in filter paper and weighed?

dry weight

53

Which method of method of counting bacteria requires the use of a light source, which is measured by whether the light reaches the detector when projected through the bacteria in a tube?

turbidity

54

Completely destroys all forms of microbial life

sterilization

55

Limited heat treatment, destroys pathogens but not all bacteria (killing C. botulinum endospores)

commercial sterilization

56

Destroys vegetative cells on a surface by reducing the number of viable organisms in the material; removal of pathogens

disinfection

57

Chemical treatment used to disinfect inanimate objects

disinfectant

58

Treatment of living skin or tissue to kill microorganisms

antisepsis

59

Physical removal of microbes (alcohol swab, soap) as in cleaning the skin prior to injections

degerming

60

Microbial contamination

sepsis

61

The absence of significant contamination

asepsis

62

What prevents microbial contamination of wounds

aseptic surgery techniques

63

Systematic cleansing of inanimate objects to reduce the microbial count to a safe level (for public health, used in restrooms, kitchens)

sanitize

64

Kill all bacteria

bactericidal

65

Halt the growth of bacteria for as long as the inhibitory substance is present

bacteriostatic

66

what determines the effectiveness of antimicrobial treatments?

Number of microbes

environment (organic matter, temperature, biofilms)

time of exposure

microbial characteristics

67

What denatures (unwinds) proteins?

heat

68

What is the time at a given temperature in which all the microorganisms in a liquid culture will be killed?

thermal death time (TDT)

69

What is the lowest temperature at which all microorganisms in a liquid suspension are killed in 10 minutes?

thermal death point (TDP)

70

Steam, pressure and heat - steam alone can reach 100 degrees Celsius but under pressure (15 p.s.i.) can reach 121 degrees Celcius

autoclave

71

Uses temperature below boiling point to kill pathogens and reduces total microorganism count (doesn't kill all, some harmless microorganisms survive), does not alter food taste

Pasteurization

72

63 degrees Celsius for 30 minutes

classical Pasteurization

73

72 degrees Celsius for 15 seconds

high temperature short-time

74

140 degrees for less than one second

ultra-high temperature

75

High temperature short-time Pasteurization

flash Pasteurization

76

Most lethal at wavelength of 260nm; absorbed by DNA, leads to formation of thymine dimers; several methods of repair; used to sterilize air, surfaces (but cannot expose skin); nonionizing radiation

ultraviolet radiation

77

Xrays, gamma rays, electron beams; penetrates deep into objects; can be used to steriize plastic objects, even foods (microwaves kill by heat; not especially antimicrobial)

ionizing radiation

78

used with heat-labile samples; physically remove bacteria from liquid or air; .45 or .2 micron pore size

filtration

79

Where does replication occur?

replication fork

80

In most bacteria, there are two forks which are moving in opposite directions what is this called?

bidirectional replication

81

occurs in a specific direction on the DNA (5' - 3')

synthesis

82

What are the two strands called?

Leading - occurring in the 5'-3' direction

Lagging - cannot synthesize continuously due to direction of DNA

83

The short pieces on the lagging strand

Okazaki fragments

84

Which strand requires RNA primers to begin each segment?

lagging strand

85

Which stand has gaps that are closed by DNA ligase

lagging strand

86

Each daughter molecule contains one original strand and one newly synthesized strand is called...

semiconservative

87

What is the sequence of translation?

U C A G down, U C A G across and U C A G going down 4 times or 1st position, 2nd position and 3rd position

88

Which is starting codon?

AUG

89

What are the stopping codons?

UAA UGA UAG

90

Triplets of bases in mRNA form

codons

91

specifies which amino acid corresponds to each codon

genetic code

92

is transcribed to make RNA (mRNA, tRNA, rRNA)

DNA

93

Begins when RNA polymerase binds to the promoter sequence

transcription

94

Proceeds in the 5' > 3' direction

transcription

95

Stops when it reaches the terminator sequence

transcrition

96

Change in the genetic material

mutation

97

May be neutral, beneficial or harmful

mutation

98

agent that causes mutation

mutagent

99

occur in the absence of a mutagent

spontaneous mutation

100

Identifies potential human carcinogens by measuring mutagenesis in bacteria

Ames Test

101

A change in the base sequence of DNA - silent if it doesn't cause a change in amino acids (often in the third position)

mutation

102

Single base substitution

point mutation

103

What are two types of point mutation?

missense and nonsense

104

change in one base and results in change in amino acid

missense

105

no length in code therefore no gene, results in a nonsense codon

nonsense

106

insertion or deletion of one or more nucleotide pairs

frameshift mutation

107

Causes the formation of ions that can react with nucleotides and the deoxyribose-phosphate backbone

ionizing radiation (x rays, gamma rays)

108

Causes thymine dimers

UV radiation

109

separates thymine dimers

light repair

110

Any bacteria picks up a "naked" DNA and it attaches to genome of new bacteria

trasnformation (recombination)

111

Two bacteria conjugate together

conjugation

112

DNA from one bacteria to another bacteria by virus

transduction

113

Segments of DNA that can move from one region of DNA to another

transposons "jumping gene"