1
Q
What is transformation?
A
Transformation is the uptake of naked DNA by a bacterial cell
2
Q
What promoter controls the GFP gene?
A
Transcription of the GFP gene is controlled by the promoer for arabinose metabolism.
3
Q
What factors effect transformation of bacteria?
A
Methods of transformation
- The method of preparation of competent cells
- the length of time of heat shock
- temperature of heat shock
- incubation time after heat shock
- growth medium used and various additives
- Bacterial colonies’ phase of growth
- Size and state of the foreign DNA
4
Q
What is meant by competency?
A
Competency is the relative ability of a bacterial cell to incorporate naked DNA (plasmid) and undergo transformation.
5
Q
Type of medium that contains reagant that will change color or react due to the growth of metabolism of bacteria.
A
Differential Media
6
Q
What type of medium is this?
Ex: The reagants in MaConkey Agar (MAC) will turn bacterial colonies pink if they are able to ferment lactose.
A
Differential Media
7
Q
What is the purpose of a selective marker?
A
Selectable markers show the success of a transfection or other procedure meant to introduce foreign DNA into a cell. It is a technique in gene targeting and gene knockout.
Ex: Beta-lactamase which confers ampicillin resistance to bacterial hosts.
8
Q
What is the purpose of the heat shock step?
A
Heat shock forms transient pores in the bacteria’s cell wall, providing a path for the plasmid (foreign DNA) to approach the bacterial cell more readily.
9
Q
Why are cells held on ice prior to heat shock?
A
10
Q
What structure is commonly used by bacteria for motility?
A
Flagella are a common physiological feature of motile bacteria
11
Q
Are all bacteria motile?
A
No but whether a bacterium is motile or non-motile can be a useful characteristic for differentiation
12
Q
You have a suspected gram-positve culture. Would it be more appropriate to grow it on MacConkey agar or PEA agar to confirm these results?
A
PEA agar, because PEA agar is selective for Gram- positive bacteria. Because the growth of Gram-negative bacteria is suppressed by the interaction of the alcohol with the outer membrane, suppressing growth.
MAC is selective for Gram negative bacteria
13
Q
In addition to selecting for halophilic bacteria, MSA can detect the fermentation of mannitol. What color will the plate turn if mannitol is fermented?
A
Yellow
If the halotolerant organism is able to ferment mannitol, the acids produced will cause the phenol red in the medium to turn yellow.
14
Q
You disover that an unidentified bacterium you have been given is Gram-negative. Would you use MAC, PEA, or MSA to determine if the bacterium ferments lactose?
A
MAC, because MacConkey Aga is selective for Gram-negative bacteria and differential in lactose fermentation.
- Not:
- PEA is selective only for Gram- postive bacteria
- MSA is selective for Gram-negative but differential for mannitol fermentation
15
Q
If an organism does not grow on MacConkey, what conclusions can you draw regarding its ability to ferment lactose.
A
No conclusions on the bacteria’s ability to ferment lactose can be drawn, since MAC is a selective and differential test.
- If an organism does not grow on the MAC agar, no conclusions can be drawn regarding lactose fermentation because selective assay takes precedence over the differential assay.
16
Q
When using selective media, why must a culture also be grown on TSA?
A
The TSA plate acts as a positve control in order to compare and differentiate among the enzymatic processes of bacteria, different media (such as selective and differentail assays) to detect metabolic and physiological differences
17
Q
What are the selective reagants in PEA?
A
Phenylethyl Alcohol
- The Gram-negative bacteria is suppressed by the interaction of alcohol with the outer membrane
- The Gram-positive bacteria are typically unaffected by the phenylethyl alcohol
18
Q
What are the selective reagants in MAC?
A
Bile salts and crystal violet
- The bile salts and crystal violet inhibit the growth of Gram-positive bacteria when compared to the TSA control plate
19
Q
What are the selective reagants in MSA?
A
7.5% NaCl
- MSA selects for halotolerant organisms, bacteria that can survive in a relatively high salt environment
20
Q
What are the differential reagents in MAC?
A
Sugar and neutral red (a pH indicator)
- If a Gram-negative organism is able to ferment lactose, the colonies will turn pink and may have a haze around them
- Gram-negative organisms unable to ferment lactose will be colorless
21
Q
What are the differential reagents in MSA?
A
Sugar mannitol and phenol red (a pH indicator)
- If a halotolerant organism is able to ferment mannitol, the acids produced will cause the phenol red in the medium to turn yellow
- Bacterial growth with no color change indicates halotolerance, but no ability to ferment mannitol
22
Q
What type of media contains reagents that will change color or react due to the growth or metabolism of bacteria?
A
Differential Media
23
Q
What is this an example of?
The reagants in MacConkey Agar (MAC) will turn bacterial colonies pink if they are able to ferment lactose?
A
Differential media
24
Q
__________ ingredients do not suppress growth, they react in response to growth.
A
Differential
25
\_\_\_\_\_\_\_\_\_\_ contain ingredients that suppress the growth of some type of organism and allow a different type of organism to grow.
Selective Media
26
Selective media are interpreted with regard to the ___________ or _________ of growth
presence or absence
27
Differential media are interpreted by the _______ or \_\_\_\_\_\_\_\_\_\_\_of the growth
color or lack of color
28
What is this an example of?
The ingredients of the MacConkey agar (MAC) suppress the growth of Gram-positve cells, while selecting the growth of Gram-negative cells.
Selective Media
29
If an organism does not grow in a selective media what conclusions can be drawn pretaining to the differential media?
No conclusions can be drawn. When using media that are selective and differential, it is important to remember that the selective assay takes precedence over the differential assay
30
What type of test is the Mannitol Salt Agar (MSA)? What does it test for?
* MSA is a selective and differential media
* MSA selects for halotolerant organisms
* Bacterial growth = halotolerant
* No growth = not halotolerant
* MSA is differential for the ability of bacteria to ferment mannitol
* Growth & Yellow = halotolerant organism that ferments mannitol
* Growth & Colorless = halotolerant organism that can't ferment mannitol
* No growth = no conclusion can be draw about fermentation
31
What type of test is PEA? What does it test for?
* PEA is selective for Gram-positive bacteria
* Not a differential test
* The presence of alcohol suppresses the growth of Gram-negative bacteria
* The presence of alcohol doesn't suppress the growth for Gram-postive bacteria
* Growth = Gram positve
* No growth = Gram negative
32
What type of test is the MacConkey Agar (MAC)? WHat does the MAC test for?
MAC is a selective and differential medium
* MAC is selective for Gram-negative bacteria
* Growth = Gram negative
* No growth = Gram positive
* MAC is differential for lactose fermentation
* Growth & pink = Gram negative bacteria that can ferment lactose
* Growth & colorless = Gram negative bacteria that cannot ferment lactose
* No growth = Gram positve but no conclusions can be drawn about fermentation
33
What is the purpose of the KOH test?
The KOH test is a **differential test** used to confirm the results of the Gram stain.
KOH causes lysis of Gram-negative bacteria (gooey)
KOH will not cause lysis of Gram-positive bacteria (watery)
34
Why does KOH become gooey in the presence of Gram-negative cells?
KOH causes lysis of Gram negative bacteria cells. After lysis, proteins and other macromolecules from the lysed cells denature, and form a thick, gooey, sticky liquid.
35
What is denaturation?
Denaturation is the break down of protein molecules.
36
As a beginning microiologist, which do you think is more reliable, a Gram stain or the KOH test?
THe KOH, because there is less steps to cause error and the results are instanteous.
37
What happens to Gram positve bacteria cell after the KOH test?
The Gram-positve cultures do not lyses, and the KOH remains watery.
38
What happens to Gram negative bacteria after the KOH test?
KOH causes lysis of the Gram-negative bacterial cells, causing the proteins and other macromolecules to denature and form a thick, gooey, sticky liquid.
39
What oxygen indicator is used in thioglycollate broth?
Resazurin acts as an oxygen indicator
(Thio-gly-coll-ate)
(Re-saz-ur-in)
40
Why is resazurin used as an oxygen indicator for thioglycollate?
Oxygen diffuses into the top portion of the thioglycollate media, which **turns the resazurin pink**, indicating that the top area of the thioglycollate broth is aerobic.
41
What component of the thioglycollate broths maintains the anaerobic conditions in the lower portion of the broth?
**Sodium thioglycollate** acts as a oxguen scrubber, maintaining an anaerobic environment in the thioglycollate medium below the pink band of resazurin.
42
Where in a thioglycollate broth tube would you expect to find growth for the following types of bacteria?
## Footnote
**Facultative anaerobes**
Throughout the tube (top and bottom)
Facultative anaerobes can use either aerobic respiration or fermentation, so can use oxygen but does not require it.
43
Where in a thioglycollate broth tube would you expect to find growth for the following types of bacteria?
## Footnote
**Obligate aerobes**
Top of the test tube only (where the resazurin is)
Obligate aerobes require oxygen for their metabolism, and are incapable of growing in an anaerobic environment, as they cannot use fermentation or anaerobic respiration.
44
Where in a thioglycollate broth tube would you expect to find growth for the following types of bacteria?
**Obligate anaerobes**
Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest.
45
Where in a thioglycollate broth tube would you expect to find growth for the following types of bacteria?
## Footnote
**Aerotolerant anaerobes**
Aerotolerant anaerobes typically use fermentation to make ATP, so they do not require nor utilize oxygen.
Aerotolerant anaerobes will grow within the lower, anaerobic portion of the broth
46
What type of metabolism is used by obligate aerobes?
Obligate aerobes use (oxygen) aerobic respiration
47
What type of metabolsim is used by facultative anaerobes?
Facultative anaerobes can use both (oxygen) respiration and (anaerobic/without oxygen respiration) fermentation
48
What type of metabolism is used by obligate anaerobes?
Obligate anaerobes can only use fermentation
49
What type of metabolism is used by aerotolerant anaerobes?
Aerotolerant anaerobes use fermentation
50
Would you expect an obligate aerobe to be capable of fermentation?
No, because obligate aerobes can only use oxygenic/ aerobic respiration, not fermentation to survive.
51
What is the substrate of gelatinase?
Gelatin (collagen)
52
Do all types of bacteria have the same oxygen requirements?
No, different types of bacteria have different oxygen requirements.
53
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ require oxygen for their metabolism and are incapable of growing in an anaerobic environment, as they cannot use fermentation or anaerobic respiration.
Obligate aerobes
54
Both ____________ and __________ will grow in an anaerobic environment.
Facultative anaerobes
Aerotolerant anaerobes
55
\_\_\_\_\_\_\_\_\_\_\_\_ can use either aerobic respiration or fermentation, so they can use oxygen but do not require it
Facultative anaerobes
56
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_typically use fermentation to make ATP, so they do not require nor utilize oxygen.
Aerotolerant anaerobes
57
\_\_\_\_\_\_\_\_\_\_\_\_ require low levels of oxygen.
Microaerophiles
58
What type of medium is used to determine the requirements of bacteria?
Thioglycollate broth
59
What does thioglycollate both contain?
Sodium thioglycollate, resuzurin, and 0.05% agar
60
What in thioglycollate both acts as an oxygen indicator?
Resazurin
61
\_\_\_\_\_\_\_\_\_\_ is a differential nutrient broth used to determine the oxygen requirements of bacteria
Thioglycollate
62
Organisms that cannot grow in anaerobic conditions, \_\_\_\_\_\_\_\_\_\_\_, will grow only in the ________ portion of the tube
* Obligate aerobes
* Upper/ top
63
Organisms that can grow anaerobically, \_\_\_\_\_\_\_\_\_\_\_and \_\_\_\_\_\_\_\_, will grow within the \_\_\_\_\_\_\_, anaerobic portion of the thioglycollate broth.
* Aerotolerant anaerobes and facultative anaerobes
* Lower/ bottom
64
What type of enzyme is secreted by bacteria (and other organisms) into their environment?
Exoenzymes
(Exo-enzymes)
65
What is another name for gelatinase?
Gelatinase is sometimes called **collagenase**
66
Gelatinase/collagenase is a type of what?
Protease
67
What enzyme catalyzes the hydrolysis of gelatin/collagen?
Gelatinase/ collagenase which is a type of protease
68
Why type of enzyme is used by a wide variety of bacteria to break down proteins for nutrient acquisition?
Exoenzymes
69
Gelatinase/ collagenase is what type of enzyme?
Exoenzyme
70
What type of differential medium is used to determine if an organism produces gelatinase?
Nutrient gelatin
71
What are the ingredients for nutrient gelatin?
Gelatin (collagen)
Peptone
Beef extract
72
If an organism produces \_\_\_\_\_\_, the exoenzyme will break down gelatin to its component amino acids and the solid gelatin will be liquid at room temperature
Gelatinase/ collagenase
73
How is gelatinase used as a virulence mechanism?
Pathogens may use enzymes like gelatinase to break down connective tissues as part of their invasion process, an important virulence mechanism
74
Why do you think agar is used to solidify media?
Agar has a higher melting point than gelatin. Gelatin is liquid at 28oC and the incubator's temperature is at 35oC, so gelatin media would not be good to track growth, like agar would.
75
How do you interpret the nutrient gelatin assay?
If an organism produces gelatinase, the exoenzyme will break down gelatin to its component amino acids and the solid gelatin will be liquid at room temperature
76
Why must observations for nutrient gelatin be done at temperatures lower that 28oC?
Gelatin is a liquid at 28oC or above
77
What type of biological molecule is collagen?
Amino acids
78
Organisms that live in an oxygen containing environment must have _________ to deak with harmful ______ \_\_\_\_\_\_\_\_.
* Mechanisms
* Oxygen radicals
79
\_\_\_\_\_\_\_\_\_\_ is an enzyme found in bacteria and other organisms that catalyzes the conversion of peroxide anions into water and oxygen, protecting the organism from oxidative damage.
Catalase
80
\_\_\_\_\_\_\_\_\_\_\_ is a differential test used to determine if a culture produces the catalase enzyme.
The catalase test
81
When hydrogen peroxide is added to a sample of bacteria on a microscope slide, if bubbles form this indicates that the organism possess what type of enzyme?
Bubbles = catalase
82
When hydrogen peroxide is added to a sample of bacteria on a microscope slide and no bubble form, this indicates that the organism...?
No bubbles = no catalase
83
If you have a positve catalase test, does this indicate that the organism is an obligate aerobe or facultative anaerobe?
No, a positve catalase test only indicates that the organism possess catalase.
Having a positive catalase test should not be interpreted as the organism being an obligate aerobe or a facultative anaerobe.
84
What is the last enzyme in the electron transport system of many organisms?
Cytochrome oxidase
85
What enzyme is responsible for reducing the oxygen in the final step of aerobic respiration, forming H2O as an end product?
Cytochrome oxidase
| (Cyto-chrome oxi-dase)
86
What is the function of catalase?
To protect the organism from oxidative damage
87
Why is bubbing used to determine if catalase is present?
The catalase enzyme will bubble when hydrogen peroxide is added to is, because it converts the peroxide anions into water and oxygen thus forming bubbles
88
What type of enzyme is secreted by bacteria (and other organisms) into their environment?
Exoenzymes
| (exo-enzymes)
89
What type of enzyme is used as toxins (like hemolysins and phospholipase) or can function to provide nutrients to the cell?
Exoenzymes
90
Exoenzymes such as __________ are used to break down large polymeric molecules into their monomers so that they may be taken into the cell.
Amylase
91
What exoenzymes are used in the brewing industry to catalyze the hydrolysis of polysaccharide amylose, starch, into smaller sugars maltose and glucose, which are then transported into the cell.
Amlyase
Glycosidase
92
Why is starch hydrolysis a useful differential assay for the characterization of unknown organisms?
Not all bacteria produce the (exo)enzymes amlyase (and glycosidase)
(am-ly-ase)
(gly-co-i-dase)
93
What differential medium is used to detect the hydrolysis of starch by a bacterial culture?
Starch agar
94
If an organism can hydrolyze starch in the starch agar, what will be seen on the plate after iodine is added?
A clear/tan area called the zone of clearing will be seen around the bacterial culture due to the absence of starch in the area immediately surrounding the bacterial growth.
95
What enzymes are used by bacteria to hydrolyze starch?
The exoenzymes:
* Amylase (amy-lase)
* Glucosidase (gluco-si-dase)
96
Why is iodine added to the starch plate?
To better see the zone of clearing if the bacteria hydrolyzes starch (produces amylase) because iodine turns starch blue/purple
97
Why does a zone of clearing form around organisms that can hydrolyze starch?
Amylase and glucosidase will "digest" starch, thus there will be a zone of clearing around the culture due to the absence of starch in the area immediately surrounding the bacterial growth.
98
Is starch agar a differential or a selective medium?
Starch agar is a differential medium because it doesn't inhibit the growth of the culture, but it does determine the culture's metabolism
99
What is a common metabolic strategy among bacteria?
Fermentation
100
In fermentation, ___________ \_\_\_\_\_\_\_\_\_\_ are used as the final electron acceptors of the metabolic pathway.
Organic molecules (contains C & H)
101
What metabolic process allows an organism to continue to oxidize NADH back into NAD+ and produce ATPs in the absence of oxygen?
Fermentation
102
What two areas is fermentation dividied into?
1. Alcohol fermentation
2. Acid fermentation
103
What type of fermentation consists of a carbohydrate ultimately being converted into organic acids?
Acid fermentation
104
What type of fermentation consists of a pathway in which: the pyruvate produced by glycolysis is decarboxylated to produce carbon dioxide and acetaldehyde, the acetaldehyde is then reduced to ethanol by alcohol dehydrogenase, and NADH is oxidized to NAD+.
Alcohol fermentation
105
What type of fermentation consists of glucose being broken down to pyruvate by glycolysis, producing 2 ATPs by substrate level phosphorylation. Pyruvate is then reduced into lactic acid by the enzyme lactate dehydrogenase. During this reduction of pyruvate, NADH is oxidized to NAD+.
Homolactic acid fermentation
106
Why type of fermentation consists of an organism fermenting a carbohydrate into lactic acid, ethanol, and gas?
Heterolactic acid fermentation
107
Do all bacteria utilize the same types of carbohydrates and use them in the same way?
No. Different species, and strains of bacteria due to their genetic makeup, do not necessarily utilize the same types of carbohydrates nor utilize them in the same way.
108
What differential test broths contain a sugar (like glucose, lactose, sucrose, or mannitol and phenol red), a pH indicator that turns from red to yellow in the presence of acid?
Phenol red carbohydrate broth
109
What is a Durham tube?
The Durham tube is a smaller, upside down tube in the Phenol red carbohydrate broth tube, used to capture any gases that may be produced during fermentation.
110
What is the purpose of the Durham tube in the phenol red carbohydrate broth tube?
To capture any gases that are produced during fermentation
111
What does it mean when the phenol red carbohydrate broth turns yellow and no bubbles have formed in the Durham tube?
The organism produces acid only
112
What does it mean when the phenol red carbohydrate broth tube turns yellow and there is a bubble in the Durham tube?
The organism ferments a sugar to produce an acid and gas
113
What does it mean if the Phenol red broth tube does not turn yellow?
The organism cannot ferment the sugar in the broth
114
What does it mean when the phenol red turns a faint orange color but not an intense yellow?
The organism may be an obligate aerobe, since obligate aerobes can convert sugars into acid, but do not employ a fermentative pathway.
Some amounts of acids may be been produced, but no fermentation occured.
115
What happens is the phenol red carbohydrate broth tube is incubated for an extended period of time?
The tue may turn from yellow back to red, this is usually seen at the top of the broth
116
What can be determined about an organism using the Phenol red carbohydrate broth tubes?
We can only determine if an acid and/or gas is produced via fermentation
117
What can the Phenol red carbohydrate broth tubes not determine about fermentation?
Does not provide any information regarding the types of acids produced (lactic, acetic) or the gas produced (CO2, H2)
118
What can be concluded by doing the Phenol red carbohydrate broth tube tests?
Only can conclude whether acid alon or acid or gas were produced
119
Phenol red turns what color in an acidic solutions?
Yellow
120
You have an unknown culture and do not have Gram stain results. You are allowed one medium to determine if it can ferment lactose. Would you use phenol red lactose broth or MacConkey agar?
Phenol red lactose broth, because we want to know if the unknown organism can ferment lactose only.
The MacConkey agar test is a selective test for Gram negative and a differential test for lactose fermentation.
We just want to know if the unknown can ferment lactose, not that if its a Gram negative or positive.
121
You have grown an obligately aerobic culture in phenol red glucose broth, and some of the media has turned yellow. How would you explain this?
Obligate aerobes can convert sugars, like glucose, into acid, but they do not employ a fermentative pathway.
122
A culture ferments mannitol and glucose to acid, but not lactose and sucrose. Is this possible? Why?
Yes, because different bacteria have different DNA, different proteins, and different enzymes therefore different metabolisms.
Different species, and strains of bacteria due to their genetic makeup, do not necessarily utilize the same types of carbohydrates, nor utilize them in the same way
123
What type of molecule is used as the final electron acceptor in fermentation?
Organic compounds (have C & H)
124
You check your fermentation broth and find that the top is red and the bottom is yellow. What can you conclude?
It means that the organism has fermented and the top portion means that the tube has been incubated for an extended period of time, which may have turned from yellow back to red
125
What is the purpose of the Durham tube?
The purpose of the Durham tube is to capture any gases that are produced during fermentation during the phenol red carbohydrate broth tube test.
126
What are the end products in each of the following types of fermentation?
## Footnote
**Alcohol fermentation by yeast**
Ethanol and carbon dioxide
127
What are the end products in each of the following types of fermentation?
## Footnote
**Homolactic fermentation**
2 ATPs and lactic acid
128
What are the end products in each of the following types of fermentation?
## Footnote
**Heterolactic fermentation?**
Lactic acid, ethanol, and gas (carbon dioxide)
129
What type of microbial control can be accomplished by using heat treatment, cold storage, disinfectants and radiation
Environmental control
130
Control in or on the a host employs the use of ________ and ____________ drugs.
* Antiseptics
* Chemotherapeutic
131
This category of microbial control includes oral and topical antimicrobias and antibiotics.
Chemotherapeutic agents
| (chemo-therap-eu-tic)
132
What is a general term for any compound that negatively affects the growth of microbes?
Antimicrobial
133
How can antimicrobials be antibacterial, antifungal, antiviral, antihelminthic, etc?
Depends on the target organism
134
What term has been historically reserved for those antimicrobials produced by organisms such as fungi and bacteria?
Antibiotic
| (anti-bio-tic)
135
What terms is used interchangeably with antibiotic?
Antimicrobial
| (anti-microb-ial)
136
What is the term used to describe some antibacterial drugs that are effective against a variety of bacteria?
Broad spectrum drugs
137
What do broad spectrum drugs usually target?
A common aspect of the bacterial cells
Ex: the drugs that attack bacterial ribosomes tend to be broad spectrum drugs
138
How do antimicrobial drugs work?
Antimicrobial drugs work because they are selectively toxic
139
What is selective toxicity?
An aspect of antimicrobial drugs in which they attack some aspect of the target cells' physiology that is not found in the host
140
Why do most antibacterial drugs not interfere with the functions within the human cells?
Because bacterial physiology differs from eukaryotic physiology
141
What kind of drug is only effective against only one or a few types of bacteria?
Narrow spectrum drugs
142
How do narrow spectrum drugs usually work?
Narrow spectrum drugs usually attack an aspect of cell physiology not found in all bacterial cells
143
The drug isoniazid affects the production of mycolic acid, and its use is limited primarily to the *Mycobacteria.*
What kind of drug is this?
Narrow spectrum drug
144
Class of drug that includes:
* streptomycin (strept-o-mycin)
* kanamycin (kana-mycin)
* neomycin (neo-mycin)
Aminoglycosides
| (amino-glyco-sides)
145
What is an ingredient in Neosporin, an over the counter antibacterial cream?
Neomycin (neo-mycin)
From the class aminoglucosides (amino-gluco-sides)
146
What is the mode of action of aminoglucosides?
(amino-gluco-sides)
To bind to the bacterial ribosomes, preventing protein synthesis
147
What antibacterials are included in the drug class aminoglucosides?
"New Kittens Sleep"
* Neomycin (neo-mycin)
* Kanamycin (kana-mycin)
* Streptomycin (strepto-mycin)
148
What class of antibacterial drugs is an antibacterial polypeptide produced by strains of ***Bacillus subtilis.***
Bacitracin (bac-i-tracin)
149
What is the mode of action for bacitracin?
Bacitracin works by preventing cell wall synthesis
150
What class of antibacterial drugs is also an ingredient in Neosporin, along with neomycin and polymyxin B?
Bacitracin
151
What class of antibacterial drugs includes:
* penicillin (pen-i-cillin)
* amoxicillin (amox-i-cillin)
Beta-Lactams
152
Beta-lactams include which antibacterials?
"A&P"
* Amoxicillin (amox-i-cillin)
* Penicillin (pen-i-cillin)
153
How is the mode of action for beta lactams?
Beta-lactams prevents the formation of peptidoglycan molecules in the bacterial cell wall.
(pepti-do-gly-can)
154
Amoxicillin is used in conjectin with what Beta-lactamase inhibitor?
Clavulanic acid
| (cla-vul-anic)
155
What Beta-lactam combination drug therapy can circumvent some resistance mechanisms?
Amoxicillin with clavulanic acid (a Beta-lactamase inhibitor)
156
What is the mode of action for chloramphenicol?
(chlor-am-phen-icol)
Chloramphenicol (chlor-am-phen-icol) disrupts protein synthesis by binding to the large ribosomal subunit
157
What is the mode of action for fluoroquinolones?
(fluoro-quin-olones)
Fluoroquinolones works by binding to the enzyme DNA Gyrase, preventing replication and killing bacterial cells
158
Ciprofloxacin is commonly used with which class of antibacterial drug?
(ci-pro-flox-acin)
Fluoroquinolones
| (fluoro-quin-olones)
159
Erythromycin (ery-thro-mycin) is under which class of antibacterial drug?
Macrolides
| (macro-lides)
160
What is the mode of action for macrolides?
(macro-lides)
Macrolides disrupt protein synthesis by binding to bacterial ribosomes
161
What group/class of antibacterials includes tetracycline?
(tetra-cycl-ine)
Tetracyclines
| (tetra-cycl-ines)
162
What is the mode of action for tetracyclines?
(tetra-cycl-ines)
Tetracyclines bind to the bacterial ribosomes and interfere with protein production
163
What group of antibacterial drugs act as competitive inhibitors of the enzymes used in the biosynthesis of folate by bacteria?
Sulfonamides/Trimethoprim
| (sulf-on-amides)/ (trime-tho-prim)
164
What type of bacteria is Bacitracin used against?
Gram positive
165
Sulfamethoxazole with trimethoprim (SxT) is an example of a combination drug. What class of antibiotic does it belong to?
(sulf-a-meth-ox-azole)
(trime-tho-prim)
Sulfonamides/ trimethoprim
(sulf-on-amids)
(trime-tho-prim)
166
What drug class is often used in combination therapy, as each antibacterial targets a different enzyme in the metabolic pathway?
Sulfonamides/ trimethoprim
(sulf-on-amides)
(trime-tho-prim)
167
What test was used in lab to test the antibacterial drug susceptbility of an organism, using paper discs impregnated with a known concentration of a specific antibiotic?
Kirby-Bauer Disk Diffusion Assay
168
If a culture is susceptible to the antimicrobial disk in the Kirby Bauer Disk Diffusion assay what will be observed?
Why?
A zone of clearing
The zone of clearing is produced because the bacterium cannot grow in the presence of the drug.
169
How is the zone of clearing measured in the Kirby Bauer Diffusion Disk assay?
The diameter of th zone of clearing is measured (in mm)
170
What information can be obtained from measuring the zone of clearing from the Kirby Bauer Diffusion Disk assay?
The diameter's length can determine the relative susceptibilties of each culture in relation to the antimicrobial used.
171
\_\_\_\_\_\_\_\_\_ __________ is a potent mutagen and microbial control agent.
Ultraviolet (UV) light
172
What causes the formation of thymine dimers in DNA molecules?
UV light
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What happens if the thymine dimers in a bacteria's DNA is not repaired?
Thymine dimers that are not repaired can block DNA replication and transcription
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Can UV light kill bacteria?
Yes, thymine dimers which left unrepaired can block DNA replication and transcriptase
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What factors of UV light affect its microbial properties?
1. Intensity of light used
2. Duration of UV exposure
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What are the limited uses of UV light?
1. Surfaces
2. Clear substrates
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Why does UV light have limited applications to surfaces and clear substrates?
UV light does not penetrate into the items being treated,
So UV light is most effective for disinfecting surfaces
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What is UV light most effective at disinfecting?
Surfaces
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What does disinfection with UV light require?
Required an adequate amount of exposure time so that the amount of DNA damage is such that the organism will die before the damage can be repaired
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Explain why UV light exposure may not be effective?
Many bacteria possess enzymes to repair UV light. If the amount of damage is minimal, the bacteria can repair the thymine dimers
181
How do you interpret the disk diffusion assay for antibacterial efficacy?
The diameter of the zone of clearing
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What would you hypothesize to explain why there may be differences in the usefulness of antibiotics on different species of bacteria?
The specific features that antibiotics target can be different between different types of bacteria cells. This makes some antibiotics less or more effective against targeting and killing the pathogenic bacteria.
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What is meant by a broad-spectrum drug?
Drug spectrum drugs usually target a common aspect of bacterial cells.
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Is UV effective control of all bacteria? Explain.
No, many bacteria possess enzymes to repair UV light damage. So if the exposure is minimal, the bacteria can repair the thymine dimers and the UV exposure will not be an effective disinfectant treatment.
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How does UV light affect bacteria?
Thymine dimers
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\_\_\_\_\_\_\_\_\_\_\_ is the uptake of naked DNA by a bacterial cell.
Transformation
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The relative ability of a bacterial cell to incorporate our plasmid is referred to as \_\_\_\_\_\_\_\_\_\_.
Competence
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\_\_\_\_\_\_\_\_\_\_\_\_ cells have the innate ability to take in DNA from the environment.
Competent
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Can all bacteria undergo natural transformation?
No
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Where are bacterical cells manipulated to induce artificial competency?
In the lab
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What is transformation?
