microbiology test 2

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1

psychrophiles

cold-loving microbes (approx -5-20 C)

2

mesophiles

moderate-temp-loving microbes (approx 10-50 C)

3

thermophiles

heat-loving microbes (approx 40-70 C)

4

minimum growth temperature

lowest temp at which species will grow

5

optimum growth temperature

temp at which species grows best

6

maximum growth temperature

highest temp at which species will grow

7

psychrotrophs

psychrophiles that have optimum growth at 20-30 C, and therefore can cause food spoilage (even in fridge)

8

hyperthermophiles

have extremely high optimum growth temps, often found in hot springs/thermal vents

9

hypertonic solution (and effect on microbes)

solution has higher concentration of solutes than is in the cell

water leaves cell, causes plasmolysis or cytoplasm shrinkage

10

hypotonic solution (and effect on microbes)

solution has lower concentration of solutes than is in the cell

water enters cell, can cause lysis

11

most bacteria grow best in a pH around ________

neutrality (6.5-7.5)

12

toxic forms of oxygen

- singlet oxygen

- superoxide radicals

- peroxide anions

- hydroxyl radicals

13

how can superoxide radicals be neutralized?

superoxide dismutase

14

how can peroxide anions be neutralized?

catalase or peroxidase

15

obligate aerobes

require oxygen to live

16

facultative aerobes

will use oxygen when present but can still grow without it

17

obligate anaerobes

can't grow in presence of oxygen

18

aerotolerant anaerobes

unable to use oxygen but can tolerate it

19

where are obligate aerobes found in tube of growth medium?

why?

clustered near the surface

highest concentration of oxygen

20

where are obligate anaerobes found in tube of growth medium?

why?

furthest from surface

no oxygen

21

where are facultative anaerobes found in tube of growth medium?

why?

mostly near surface but still throughout entire tube

best growth occurs with oxygen but it's not needed

22

where are aerotolerant anaerobes found in tube of growth medium?

why?

event throughout tube

oxygen level has no effect

23

how do obligate aerobes avoid toxic forms of oxygen?

use enzymes (SOD and catalase) to neutralize it

24

how do facultative anaerobes avoid toxic forms of oxygen?

use enzymes (SOD and catalase) to neutralize it

25

why can't obligate anaerobes utilize oxygen?

lack the enzymes needed to neutralize toxic oxygen

26

why can aerotolerant anaerobes tolerate oxygen?

have one enzyme (SOD) to partially neutralize toxic forms

27

quorum sensing

chemical communication used between cells within biofilm

28

chemically defined media

have exact known chemical composition

29

complex media

have unknown exact chemical composition

30

how to culture anaerobic microbes?

use reducing media or keep them in a special chamber that lacks oxygen

31

reducing media

media containing ingredients that chemically deplete oxygen levels

32

differential media

makes it easier to distinguish colonies of desired organism from others on plate

33

selective media

designed to suppress growth of unwanted organisms and encourage growth of desired ones

34

blood agar

differential media that contains RBCs, used to identify microbes that destroy RBCs

35

mannitol salt agar

media that differentiates between bacteria that can ferment mannitol and those that can't

also selects for bacteria that can grow in high salt content

36

enrichment media

used for preliminary isolation that favors growth of desired organisms, or to boost colonial growth

37

two methods of culture preservation

- deep freezing

- lyophilization (freeze drying)

38

how do bacteria reproduce?

binary fission (DNA is replicated and thing splits in two)

39

generation time

time required or cell population to double in number

40

four phases of bacterial growth

1. lag phase

2. log phase

3. stationary phase

4. death phase

41

lag phase

bacteria are adjusting to media and preparing to grow but do not yet

42

log phase

bacterial population grows exponentially

43

stationary phase

period of bacterial population equilibrium (births = deaths)

44

death phase

bacterial population decreases exponentially

45

population number = ?

# of cells / mL of liquid (or gram of solid)

46

sepsis

bacterial contamination

47

asepsis

absence of bacteria

48

antisepsis

destroying harmful bacteria from living tissue

49

sterilization

removal/destruction of all microbial life

50

commercial sterilization

killing Clostridium botulinum endospores from canned food

51

disinfection

destroying harmful microorganisms, but not all life

52

degerming

mechanical removal of microbes from limited area

53

sanitization

lowering microbial counts to safe public health levels (e.g. on eating utensils)

54

biocidal

describes treatments that kill microbes

55

bacteriostatic

describes treatments that inhibit microbial growth, but don't kill them

56

effectiveness of microbial control treatment depends on _______ (4)

- number of microbes

- environment

- time of exposure

- microbial characteristics

57

D-value

decimal reduction time

time in minutes to kill 90% of bacteria at a given temperature

58

if there is a population of 1014 bacteria, what D treatment would be useful for eliminating most of them?

14D treatment

59

how does moist heat kill microorganisms?

denatures proteins by breaking H-bonds

60

pasteurization

kills spoilage microorganisms without seriously affecting a food's taste

61

filtration

substance passes through filter with pores small enough to retain microbes

method of heat-sensitive sterilization

62

effect of low temperature treatments on bacteria

decrease metabolic reactions, induce bacteriostasis

63

how is high pressure used to control microbial levels?

what is an advantage?

alters the structure of proteins and carbohydrates, inactivating cells

preserves flavors, colors, nutrients in products

64

physical methods of food preservation (5)

- low temperatures

- high pressure

- desiccation (lyophilization)

- osmotic pressure

- ionizing radiation

65

how is ionizing radiation used to control microbial levels?

gamma rays, X rays, electron beams are used to ionize water and form hydroxyl radicals -> damage DNA

66

how is non-ionizing radiation used to control microbial levels?

UV light is used to create extra bonds in DNA, prevents proper replication

67

effective chemical disinfection can be influenced by _______ (4)

- concentration of disinfectant

- presence of organic matter

- pH

- time

68

use-dilution test

method of evaluating effectiveness of disinfectants via serial dilution

69

disk-diffusion method

test to determine microbial susceptibility to chemotherapeutic agents

70

zone of inhibition

area of no bacterial growth

forms when a disk containing effective chemical agent is placed on bacterial culture

71

phenolics

1. MOA

2. best for

1. disrupt lipid-containing plasma membranes

2. mycobacteria

72

bisphenols

1. MOA

2. best for

1. disrupt lipid-containing plasma membranes

2. gram-positive staphylococci and streptococci

73

biguanides

1. MOA

2. best for

1. disrupt plasma membranes

2. skin and mucous membranes

74

iodine

1. MOA

2. best for

1. impairs protein synthesis

2. skin and wound treatment

75

chlorine

1. MOA

2. best for

1. forms HOCl and alters cell

2. disinfecting sources of water, food-related equipment

76

alcohols

1. MOA

2. best for

1. denatures proteins, dissolves lipids

2. degerming skin before injections, enhancing effectiveness of other chemical agents

77

heavy metals

1. MOA

2. best for

1. oligodynamic action to denature proteins

2. biocidal or antiseptic effects

78

surfactants

decrease surface tension among molecules of a liquid

includes soaps/detergents, acid-anionics, and quats

79

soaps/detergents

1. MOA

2. best for

1. mechanical removal of dirt and microbes

2. gently removing contaminants

80

acid-anionics

1. MOA

2. best for

1. disrupt plasma membranes

2. cleaning food processing equipment

81

quats

1. MOA

2. best for

1. affect cell's permeability

2. strong biocidal effect against gram positive bacteria

82

chemical methods of food preservation (2)

- organic acids

- nitrates/nitrites

83

aldehydes

1. MOA

2. best for

1. inactivate proteins

2. preservation of specimens, disinfection of hospital equipment

84

common chemical sterilants (2)

- ethylene oxide gas

- hydrogen peroxide gas

85

plasma sterilization

excited gas particles emit free radicals that destroy microbes

86

peroxygens

1. MOA

2. best for

1. oxidation

2. disinfection of inanimate objects/surfaces

87

why are biocides usually less effective against gram-negative bacteria?

presence of external lipopolysaccharide layer in cell wall

88

which two gram-negative genera are especially hard to kill?

why?

Pseudomonas and Burkholderia

they have specially structured porins that resists entry of particles into cell

89

why are mycobacteria so resistant to biocides?

cell walls contain lipids

90

tuberculocidal

describes treatments that are effective against mycobacteria

91

what is the difference between enveloped and non-enveloped viruses that influences how easy they are to kill?

enveloped viruses have lipid coat that is susceptible to wider range of antimicrobials (easier to kill)

non-enveloped viruses have protein coat that is more resistant to biocides (harder to kill)

92

chemotherapy

treatment of disease with chemical substances

93

selective toxicity

ability of antimicrobial agent to target pathogens without damaging the host

94

term for totally synthetic drugs meant to inhibit microbes?

antimicrobial drug

95

term for natural substance produced by microbes to inhibit other microbes?

antibiotic

96

more than half of antibiotics are produced by what?

Streptomyces species

97

broad spectrum

describes antibiotic drug that affects a large range of organisms

98

narrow spectrum

describes antibiotic drug that affects a small range of organisms

99

5 main actions of antimicrobial drugs

- inhibition of cell wall synthesis

- inhibition of protein synthesis

- inhibition of nucleic acid replication

- inhibition of metabolite synthesis

- injury to plasma membrane

100

antibiotics that interfere with protein synthesis (4)

- chloramphenicol

- erythromycin

- tetracycline

- streptomycin

101

antibiotics that interfere with cell wall synthesis (4)

- penicillins

- cephalosporins

- bacitracin

- vasomysin

102

antibiotics that interfere with metabolite synthesis (2)

- sulfanilamide

- trimethoprim

103

antibiotic that causes injury to plasma membrane

polymyxin B

104

chloramphenicol MOA

binds to 50S portion of ribosome, inhibits formation of peptide bond

105

tetracycline MOA

interfere with attachment of tRNA to mRNA-ribosome complex

106

how do antibiotics inhibit metabolite synthesis?

antimetabolites resemble the normal substrate for an enzyme (e.g. PABA), allowing them to competitively inhibit that enzyme's action (e.g. folic acid production)

107

common structure found in all penicillins

nucleus containing beta-lactam ring

108

penicillinase

enzymes produced by many bacteria that inhibit activity of beta-lactam ring

109

penicillin MOA

beta-lactam ring prevents successful cross-linking of peptidoglycans (and therefore inhibits cell wall synthesis)

110

2 broad spectrum penicillins

- ampicillin

- amoxicillin

111

vancomycin

polypeptide antibiotic that was considered last line of defense against MRSA (but not so much anymore)

112

2 major anti-mycobacterial antibiotics and what they do

- isoniazid, inhibits synthesis of mycolic acids

- ethambutol, prevents integration of mycolic acids into cell wall

113

lipopeptides

antibiotics that cause damage to plasma membrane (e.g. polymyxin B)

114

E test

modified disk diffusion test

involves placing a stick containing increasing concentrations of an antibiotic into bacteria, determining the minimal inhibitory concentration

115

broth dilution test

determines if antibiotic is bactericidal or bacteriostatic

involves multiple wells containing bacteria + increasing concentrations of antibiotic, seeing at which concentration bacteria are killed (minimal bactericidal concentration)

116

antibiogram

reports that record susceptibility of organisms encountered clinically

117

4 major mechanisms of antibiotic resistance in cells

- prevention of drug's entry into cell

- enzymatic deactivation of drug

- alteration of drug's target site

- efflux of drug out of cell

118

therapeutic index

assessment of a drug's risk/benefit ratio, contraindications, side effects

119

synergism

when the combined effect of multiple antibiotics is greater than that of either one alone

120

antagonism

when the combination of multiple antibiotics is less effective than just one of them alone

121

gene

DNA segment that codes for a functional product

122

central dogma of molecular bio

DNA > transcription > RNA > translation > protein

123

gene expression

production of functional product through transcription and translation

124

base substitution

mutation where a single bp at one point in DNA sequence is replaced by another

125

frameshift mutation

mutation where one or more bps are deleted or inserted into the DNA sequence

126

missense mutation

base substitution that leads to insertion of incorrect amino acid

127

nonsense mutation

base substitution that leads to premature insertion of STOP codon

128

vertical gene transfer

aka replication

flow of genetic information from one generation to the next

129

horizontal gene transfer

aka recombination

flow of genetic information between cells of same generation

130

bacterial transformation

genes transferred from one organism to another as "naked" DNA in solution

131

competence

ability of recipient cell to take up donor DNA

132

conjugation

transfer of genes via direct cell to cell contact

133

F factor

fertility factor

plasmid that permits its own transfer from one (F+) bacterium to another via formation of sex pili

134

what must be true of two cells engaged in conjugation?

they are of opposite mating type (donor cell contains plasmid, recipient cell does not)

135

Hfr cell

cell that receives F factor via conjugation and integrates it into its chromosome

136

what results from conjugation between F+ and F- cells?

both will end up F+

137

what results from conjugation between Hfr and F- cells?

F- cell integrates Hfr cell's DNA into its own chromosome, becomes recombinant F- cell

138

transduction

transfer of genes between cells via bacteriophage

139

generalized transduction

random chromosome fragments are packaged within phage and transferred to donor cell

140

specialized transduction

only certain chromosome fragments are packaged within phage and transferred to donor cell

141

what kind of operon is the lac operon?

inducible (and catabolic)

142

inducible operon

transcription is turned off unless molecule of interest is present

143

repressible operon

transcription is turned on unless molecule of interest is present

144

nucleotide

sugar + base + phosphate

145

nucleoside

sugar + base

146

how many H bonds between base pairs?

two between A and T

three between C and G

147

replica plating

method of negative indirect selection (identifies a mutant that cannot perform a specific function)

148

Ames reverse gene mutation test

determines if a given substance is a mutagen

done by applying the substance to cells and seeing how many colonies are revertant

149

revertant bacteria

mutant bacteria that, after being re-exposed to a mutagen, revert back to original state

150

DNA gyrase

topoisomerase - relaxes supercoiling ahead of replication fork

151

DNA ligase

makes covalent bonds to join DNA strands

152

topoisomerase

relaxes supercoiling ahead of replication fork (e.g. DNA gyrase)

153

helicase

unwinds double-stranded DNA

154

primase

RNA polymerase that makes RNA primers from a DNA template

155

DNA polymerase

synthesize DNA, proofread and facilitate repair of DNA

156

which end of a nucleotide is the 3' end?

where -OH attaches to 3' carbon

157

which end of a nucleotide is the 5' end?

where phosphate attaches to 5' carbon

158

to which end do polymerases add new nucleotides?

3' end

159

how often is a mistake made in DNA replication?

once in every 10 billion bases

160

where does the energy needed for DNA replication come from?

new nucleotides being added have 3 phosphates - two are hydrolyzed and release energy while the other is attached to -OH

161

two components needed for transcription (apart from DNA)

- RNA polymerase

- RNA nucleotides

162

codon

group of three nucleotides that correspond to an amino acid

163

tRNA

transfer RNA

contains anticodon that complements a codon in mRNA and transports required amino acid

164

operon

group of genes that are transcribed together and controlled by one promoter

165

promoter

location on operon where RNA polymerase initiates transcription

166

operator

part of operon where repressor protein binds

167

repressor protein

protein that interacts with operator to allow or inhibit transcription

168

corepressor

in repressible operon, a molecule that binds to repressor and enables it to bind to operator