Lecture 9: Microbial Growth and Control (Ch7,8,and 9) Flashcards Preview

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Flashcards in Lecture 9: Microbial Growth and Control (Ch7,8,and 9) Deck (131):
1

The reproductive strategies of eukaryotic microbes

-- Asexual and sexual, haploid and diploid

2

Reproductive strategies of bacteria and Archaea

- Haploid only, asexual- binary fission, budding, filamentous - All must replicate and segregate the genome prior to division

3

most bacteria divide by

binary fission

4

what are the two pathways that cycle during binary fission

- DNA replication and partition - Cytokinesis

5

Reproduction in prokaryotes

- Binary fission - Budding - Conidiospores (actinomycetes) - Fragmentation of filaments

6

What is generation time

(doubling time) is the time it takes for a population to double

7

A population of microbes that doubles at a constant rate is an example of

exponential growth

8

What are the 4 phases of the growth curve

- Lag phase - Exponential (log) phase - Stationary phase - Death phase

9

What occurs during the lag phase of the growth curve

- Cell synthesizing new components

10

What occurs during the exponential phase of the growth curve

- growth and division is constant and maximal - population is most uniform in terms of chemical and physical properties during this phase

11

What occurs during the stationary phase of the growth curve

- closed system population growth eventually ceases, total number of viable cells remains constant. (active cells stop reproducing or reproductive rate is balanced by death rate)

12

Generation (doubling) time varies depending on

species of microorganism and environmental conditions

13

The range of generation (doubling) time is from ____ minutes for some bacteria to _______ for some eukaryotic microorganisms

10 minutes for some bacteria to several days for some eukaryotic microorganisms

14

Direct methods for measuring microbial growth

- Plate counts - Filtration - MPN (most probable number) - Direct microscopic count

15

What are the indirect methods for measuring microbial growth

- Turbidity - Metabolic activity - Dry weight

16

how to perform viable counting with spread and pour plate techniques

- Spread and pour plate techniques (the difference is one you spread out and the other you add melted nutrient agar and swirl to mix) ( note that in the spread they only grow on the surface and in the pour method they go on and in the medium) (the pour plate method is used with anaerobes because they can grow under the agar) - Diluted sample of bacteria is spread over solid agar surface or mixed with agar and poured into Petri plate - After incubation the number of organisms are determined by counting the number of colonies multiplied by the dilution factor - Results expressed as colony forming units (CFU)

17

viable counting via the membrane filter technique

- bacteria form aquatic samples are trapped on membranes - membrane soaked in culture media - colonies grow on membrane - colony count determines number of bacteria in sample

18

If a microbe cannot be cultured on plate media then

dilutions are made and added to suitable media (turbidity determined to yield the most probable number (MPN))

19

bacterial growth can be measured with a _____, which measures the absorbance at 600nm

spectrophotome

20

Do bacteria have limited control over their internal environments

Yes. This is why the environmental factors affect microbial growth

21

Requirements for growth can be divided among ___ and ____ requirements

Physical and chemical requirements

22

What are some physical requirements that regulate bacterial growth

- Temperature - pH - Osmotic pressure

23

What some of the chemical requirements that regulate bacterial growth

- Carbon - nitrogen, sulfur, phosphorous - Trace elements - Oxygen - Organic growth factor

24

Examples of osmotolerant microorganisms

- Staphylococcus aureus - Saccharomyces rouxii

25

Examples of Halophile (requires high levels of sodium chloried, usually above about 0.2M, to grow)

- Halobacterium, Dunaliella, Ectothirohodospira

26

examples of Acidophile (Growth optimum between pH 0 and 5.5)

- Sulfolobus - Picrophilus - Ferroplasma - Acontium

27

Temperature range of psychrophiles

0- 20 degrees C

28

temperature range of psychrotrophs

0-35 degrees C

29

Temperature range of mesophiles

20-45 degrees C

30

Temperature range of thermophiles

55-85 degrees C

31

Temperature range of hyperthermophiles

85- 113 degrees C

32

Danger zone for bacterial growth

- 15-50 degrees C - 60-130 degrees F

33

What are the cardinal temperatures

Minimum, maximum, and optimum temperature

34

Adaptations of thermophiles

- Protein structure stabilized by a variety of means: more H bonds, more proline, and chaperones - Histones- like proteins stabilize DNA - Membrane stabilized by variety of means (more saturated, more branched and higher molecular weight lipids, ether linkages (archaea like membranes)

35

Most bacteria grow between pH ____ and ____

6.5 and 7.5

36

Molds and yeasts how between pH ___ and ___

5 and 6

37

______ grow in acidic environments

Acidophiles

38

What is the optimum pH for acidophilus

pH 0 and pH 5.5

39

Neutrophils growth is optimum between pH ____ and _____

pH- 5.5 and pH 7

40

Alkaliphiles (alkalophiles) growth optimum is between

pH 8.5 and pH 11.5

41

Toxicity is a measure of ______

Osmotic pressure (hypertonic, isotonic, hypotonic)

42

Hypertonic environments, or an increase in salt or sugar, cause _____

Plasmolysis

43

Halophiles grow optimally at

NaCl concentration greater than 0.2 M

44

Extreme Halophiles require NaCl concentration

Greater than 2 M

45

Chemoheterotrophs use ______ carbon sources

Organic

46

Autotrophs use _____ carbon sources

CO2

47

Osmotolerant

Able to grow over wide ranges of water activity or osmotic concentration

48

Halophile

Requires high levels of sodium chloride, usually above about 0.2 M, to grow

49

Obligate aerobe

Completely dependent at atmospheric O2 for growth

50

Facultative anaerobe

Does not require O2 for growth but grows better in its presence

51

Facultative anaerobe

Does not require O2 for growth but grows better in its presence

52

Aerotolerant anaerobe

Grows equally well in presence or absence of O2

53

Obligate anaerobe

Does not tolerate O2 and dies in its presence

54

Microaerophile

Requires O2 levels between 2-10% for growth and is damaged by atmospheric O2 levels (20%)

55

Growth more rapid at high hydrostatic pressures

Piezophile (basophile)

56

Nitrogen requirements

- nitrogen is in most amino acids and proteins - most bacteria decompose proteins - Some bacteria use NH4+ or NO3- - A few bacteria use N2 in nitrogen fixation

57

Sulfur requirements in bacteria

- in amino acids, thiamine, and biotin - Most bacteria decompose proteins - Some bacteria use SO4^2- or H2S

58

Phosphorus requirements in bacteria

- in DNA, RNA, ATP, and membranes - PO4^3- in a source of phosphorus

59

______ is a measure of the ability of a microorganism to grow in the presence or absence of oxygen

Aerotolerance

60

Oxygen easily reduced to ________

- toxic reactive oxygen species (ROS) - Superoxide radical - Hydrogen peroxide - hydroxyl radical

61

Aerobes produce protective enzymes such as ____. ____ , and ____ to neutralize toxic reactive oxygen species (ROS)

- Superoxide dismutase (SOD) - Catalase - Peroxidase

62

what is singlet oxygen: O2-

normal molecular oxygen (O2) boosted to a higher-energy state

63

Superoxide free radicals: O2 - is reduced by _____ to H2O2 + O2

Superoxide dismutase

64

Peroxide anion can be removed via enzymes

Catalase or peroxidase

65

all strict anaerobic microorganisms lack or have very low quantities of

- Superoxide dismutase and catalase

66

Anaerobes must be grown without ____

O2 (work station with incubator, gaspak anaerobic system)

67

What are capnophiles

organisms that require higher than normal atmospheric levels of CO2

68

Olbligate aerobes contain what enzymes

- SOD (+) - catalase (+)

69

Facultative anaerobes contain what enzymes

- SOD (+) - Catalase (+)

70

Aerotolerant anaerobes contain what enzymes

- SOD (+) - Catalase (-)

71

Strict anaerobe enzymes

- SOD (-) - Catalase (-)

72

Microaerophile enzymes

- SOD (+) - Catalase (+/-) (low levels)

73

Adversely affected by increased pressure, but not as severely as non tolerant organisms

Barotolerant

74

Barophilic (peizophilic) organisms

- Require or grow more rapidly in the presence of increased pressure - Change membrane fatty acids to adapt to high pressures

75

Destruction or removal of all viable organisms

Sterilization

76

Killing, inhibition, or removal of disease causing (pathogenic) organisms

Disinfection

77

What are some disinfectants

- agents, usually chemical, used for disinfection - usually used on inanimate objects

78

Reduction of microbial population to levels deemed safe (based on public health standards)

Sanitization

79

Prevention of infection of living tissue by microorganisms

Antisepsis

80

Chemical agents that kill or inhibit growth of microorganisms when applied to tissue

Antiseptics

81

Use of chemicals to kill or inhibit growth of microorganisms within host tissue

Chemotherapy

82

Agents that kill microorganisms or inhibit their growth

- cidal agents kill - static agents inhibit growth

83

- suffix indicating that agent kills

-cide

84

Kills pathogens and many no pathogens but not necessarily endospores

Germicide

85

Suffix indicating that agent inhibits growth

-static

86

What is decimal reduction time

Time to kill 90%

87

What are persisted cells

- Viable but nonculturable (VBNC) condition - once they recover they may regain the ability to reproduce and cause infection

88

The pattern of microbial death

- Microorganisms are not killed instantly - population death usually occurs exponentially

89

Conditions influencing the effectiveness of anti microbial agent activity

- Population size (larger populations take longer to kill than smaller populations) - Population composition (microorganisms differ markedly in their sensitivity to anti microbial agents) - Concentration or intensity of an anti microbial agent (usually higher concentrations kill more rapidly but this relationship is not linear) - Duration of exposure (longer exposure means more organisms killed) - Temperature- higher temperatures usually increase killing - Local environment (pH, viscosity, concentration of organic matter, etc. can profoundly impact effectiveness)(organisms in bio films are less susceptible to many anti microbial agents)

90

Filtration reduces microbial population or sterilizes solutions of _______ by _______. Also used to reduce microbial populations in air

Heat-sensitive materials by removing microorganisms

91

Porous membranes with defined pore sizes that remove microorganisms primarily by physical screening

Membrane filters

92

Filtering air by use of

- Surgical Masks - Cotton plugs on culture vessels - High- efficiency particulate air (HEPA) filters- used in laminar flow biological safety cabinets

93

Physical control methods

- heat - Radiation

94

Moist heat destroys

- Viruses, fungi, and bacteria - boiling will not destroy spores and does not sterilize - Degrades nucleic acids, denatures proteins, and disrupts membranes

95

Moist heat will not destroy ___ and does not ____

Spores and does not sterilize

96

Steam sterilization is carried out above ____ which requires saturated stream under pressure

100 degrees C

97

stream sterilization uses _____ and is effective against

autoclave, all types of microorganisms (including spores)

98

Pasteurization is controlled heating at temperatures

Well below boiling

99

Pasteurization does not ______ but does _____

sterilize but does kill pathogens present and slow spoilage by reducing the total load of organisms present 

100

Dry Heat Sterilization is ____ effective than moist heat sterilization, requiring ____

less, requiring higher temperatures and longer exposure times (items subjected to 160-170 degrees C for 2 to 3 hours) 

101

Dry heat sterilization  ____ cell constituents and _____ proteins 

oxidizes, denatures 

102

_______ are used to sterilize inoculating loops used in microbiology laboratories 

Bench top incinerators

103

What UV wavelenth is is mot bactercidal 

260 (DNA absorbs) 

104

UV radiation cause ____ dimers preventing replication and transcription

thymine 

105

UV limited to surface surface sterilization because

it does not penetrate glass, dirt films, water, and other substances 

106

Gamma radiation penetrates ____ into objects 

deep 

107

Ionizing radiation (gamma radiation) destrosy ____ but is not always effective against 

bacterial endospores; viruses

108

Ionizing radiation is used for _____ and pasterization of ____, _____, ____, _____, and ____

sterilization, antibiotics, hormones, sutures, plastic disposable supplies, and food

109

What to consider when using a disinfectant

  • Concentration of disinfectant
  • organic matter (this can interfere with a disinfectant) 
  • pH 
  • Time

110

Phenolics

  • commonly used as laboratory and hospital disinfectants
  • Act by denaturing proteins and disrupting cell membranes
  • Tuberculocidal, effective in presence of organic material, and long lasting
  • Disagreeable odor and can cause skin irritation 

111

Alcohols

  • Among the most widely used disinfectants and antiseptics
  • Two most common are ethanol and isopropanol
  • Bactericidal, fungicidal, but not sporicidal 
  • Inactive some viruses
  • Denature proteins and possibly dissolve membrane lipids

112

Ethanol and isopropanol require 

Water

113

Iodine

  • Skin antiseptic
  • oxidizes cell constituents and iodinates proteins
  • At high concetrations may kill spores
  • Skin damage, staining, and allergies can be a problem
  • Iodophore
    • Iodine complexed with organic carrier
    • released slowly to minimize skin burns

114

Chlorine

  • Oxidizes cell constituents
  • Important in disinfection of water supplies and swimming pools, used in dairy and food industries, effective household disinfectant
  • destroys vegetative bacteria and fungi
  • Chlorine gas is sporicidal 
  • Can react with organic matter to form carcinogenic compounds 

115

Heavy metals

  • Ions of mecury, silver, arsenic, zinc, and copper
  • Effective but usually toxic
  • Combine with and inactivate proteins; may also precipitate proteins 

116

Quaternary Ammonium Compounds 

  • Detergents that have antimicrobial activity and are effective disinfectans (amphipathic organic 
  • Cationic detergents are effective disinfectants 
    • Kill most bacteria, but not M. tuberculosis or endospores
    • Safe and easy to use, inactivated by hard water and soap

117

Aldehydes 

  • Commonly used agents are formaldehyde and glutaraldehyde
  • highly reactive molecuels 
  • Sporicidal and can be used as chemical sterilants 
  • Combine with and inactivate nucleic acids and proteins 

118

Phenol Coefficient Test 

  • Potency of a disinfectant is compared to that of phenol 
  • useful for screening but may be misleading

119

120

Dilution test

121

dilution test

determines rate at which selected bacteria are destroyed by various chemical agents 

122

Method for evaluating the effectiveness fo disinfectants 

  • Metal rings dipped in test bacteria are dried
  • Dried cultures are placed in disinfectant for 10 minutes at 20 degrees C
  • Rings are transferred to culture media to determine whether bacteria survived treatment

123

normal in-use testing

-testing done using conditions that approximate normal use of disinfectant 

124

Streptomycin

  • anitbiotic active against tuberculosis

125

General characteristics of antimicrobial drugs

  • Selective toxicity
  • Therapeutic dose
  • Toxic dose
  • Therapeutic index

126

Selective toxicity

ability of drug to kill or inhibit pathogen while damaging host as little as possible

127

Drug level required for clinical treatment

Therapeutic dose

 

128

Drug level at which drug becomes too toxic for patient (produces side efects)

Toxic dose

129

Ratio of toxic dose to therapeutic dose

Therapeutic index

130

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