Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Clinical Bacteriology (Laboratory) > Bacterial Quantification by Culture (Labster Lab Manual | M) > Flashcards

Bacterial Quantification by Culture (Labster Lab Manual | M) Flashcards

1
Q

Can a bacterial population expand at an exponential rate in ideal conditions?

A

Yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

If a single E.coli can spawn a population over 1 B strong in a 10 hr timeframe, what is the optimal generation time (roughly) for this to happen?

A

Roughly 20 mins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Can a single E. coli spawn a population over 1 B strong in a 10 hr timeframe?

A

Yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the result of the rapid growth of E. coli (in a 10 hrs timeframe)?

A

It can transform a tube w/ clear growth medium into a hazy solution in the course of a day

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How to express the exponential progression of E. coli?

A

2^n

*a simple expression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does ‘n’ from 2^n represents?

A

It represents the # of generations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

At the start, the initial bacteria (in exponential form) is equal to what?

A

2^0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

After 3 generations, the population will expand to what?

A

2^3 or 2 X 2 X 2

so it is equivalent to 8 cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How to calculate the generation time of the bacterial population?

A

Execute the simple mathematics of the exponential growth of bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Is the bacterial growth (exponentially) spontaneous nor constant and follows distinct growth curves?

A

Yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is CFU?

A

It is a measurement to estimate the # of viable bacteria or fungal cells in a sx

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

When is a cell only considered viable?

A

If it is able to multiply via binary fission under controlled conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How to calculate CFUs?

A

These can be calculated by spreading a sp volume of the microbial culture onto an agar plate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What happens after incubating the agar plate?

A

The # of colonies is proportional to the # of viable colonies in the tube

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Explain how to compute the CFU per mL of a bacterial culture

A

Ex.
If 0.1 mL of a bacterial culture results in 25 colonies. The CFUs per mL can be calculated as follows:

cfu / mL = colonies / volume spread 25 colonies / 0.1 mL = 250 cfu / mL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Can a bacterial culture containing many viable cells be counted directly?

A

No

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What should be done if there are many viable cells present in a bacterial culture?

A

In this case, you need to perform a serial dilution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Why should serial dilution be done?

A

In order to decrease the # of cells that you use for spreading

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How to calculate the cfu / mL of a diluted sx?

A

Multiply the # of colonies w/ the dilution factor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the other techniques that can be used to quantify the # of bacteria in a sx?

A

Examination w/ a microscope

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is required (or criteria) if the # of bacteria in a sx is quantified via examination w/ microscope?

A

These alternative methods require significant growth and also don’t exclude dead or non-viable cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the importance of serial dilutions?

A

These are useful when we want to obtain a very diluted solution from very concentrated stock solutions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

If we want to obtain 10 mL of 1 mM (M?) solution from a 1 M stock solution, compute the value (volume) for direct dilution

A

M1V1 = M2V2
V1 = M2V2/M1
= (10 mL X 1/1000M) /1M
= 0.01 mL

Water to add: 10 mL - 0.01 mL = 9.99 mL

In these cases, direct dilution is not very helpful because it would be difficult to pipette exactly 9.99 mL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

For serial dilution, what is done?

A

We first look at the final volume and concentrations needed, then determine the dilution factor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
If we need 10 mL of a 1mM solution, what is the dilution factor?
Dilution factor = 1/ (final concentration/ initial concentration) = 1/ (0.001 M/ 1 M) = 1000X We can split up 1000X into multiple factors: 10 X 10 X 10 This means we can set up 3 tubes to perform the serial dilution. When it is a 10X dilution, it means that it is 1 part of the solution, 9 parts of the diluent (usually it is water). Similarly, for a 15X dilution, it will be 1 part of the solution, 14 parts of the diluent
26
What is usually used as a diluent?
H2O
27
How is the process (or principle) of serial dilution done?
10 mL stock solution (1 M) + 1 mL to 9 mL diluent (0.1 M) + 1 mL to 9 mL diluent (0.01 M) + 1 mL to 9 mL diluent (0.001 M) 1 mL of stock is transferred to the 2nd tube that contains 9 mL of diluent (ex. H2O). Then 1 mL (aliquot) of the 2nd tube is taken and transferred to the 3rd tube. The process of transferring aliquot is repeated until the desired dilution concentration is achieved
28
True or False. Although serial dilution requires more preparation, it will give more accurate dilutions, provided that your technique is precise
True
29
What is ensured via the application of sterile technique?
It is used to ensure a "clean" lab environment
30
What is the importance of application of sterile technique?
It is essential to ensure the reliability of experimental results
31
When are sterile practices especially important?
When working w/ microorganisms
32
Can a single spore or tiny bacterium overgrow the whole medium and destroy the exp?
Yes
33
What are the steps used to keep lab work sterile?
1) Lab doors and windows are kept closed to prevent air currents, preventing surface microorganisms becoming airborne 2) The wire loop and glass spreader are sterilized before and after use w/ a Bunsen burner to prevent the introduction of unwanted microorganisms 3) Lids from bottles and tubes are held when removed, and not placed on the bench during mat transfer from one bottle or tube to another 4) The neck of a bottle or tube must be immediately heated using the Bunsen burner so that any air movement is outward 5) The bottle or tube are opened for the minimum time possible, and while open, all work is performed close to the Bunsen burner flame 6) Media and equipment are sterilized to prevent the growth of unwanted microorganisms
34
What should be done to prevent surface microorganisms becoming airborne?
Lab doors and windows are kept closed to prevent air currents, hence, preventing surface microorganisms becoming airborne
35
What should be done to the wire loop and glass spreader before and after use?
These should be sterilized
36
What should be done to lids from bottles and tubes when removed?
The lids from bottles and tubes are held when removed, and not placed on the bench during mat transfer from one bottle to another
37
What is the purpose of heating the neck of the bottle immediately using the Bunsen burner?
So that any air movement is outward
38
Can the bottle or tube opened all the time during the lab procedure?
No, the bottle or tube are opened for the minimum time possible
39
What should be done to the media and equipment to prevent the growth of unwanted microorganisms?
These should be sterilized
40
What is antibiotic resistance?
It is the general process in w/c bacteria (usually infectious) becomes insensitive to a sp drug or a sp class of drugs
41
When do antibiotic resistance usually appear?
When a microbe is exposed to sub-lethal concentrations of a sp antibiotic: due to selective pressure, the surviving microbes might develop resistance mechanisms across several generations through mutations in their DNA
42
How are the surviving microbes (in antibiotic resistance) might develop resistance mechanisms across several generations through mutations in their DNA?
Due to selective pressure
43
The resistance mechanisms can be sorted into how many categories?
4
44
What are the categories of the resistance mechanisms?
1) The modification of the primary target of the antibiotic, such as the transpeptidase for ampicillin resistance 2) The inactivation of the antibiotic compound itself, such as the production of B-lactamase enzymes to degrade penicillin G inside the cell 3) Preventing the antibiotic from reaching the target, by reducing the permeability of the membrane or using efflux pumps to keep the drug outside the cell, as observed against ciprofloxacin for example 4) Using alternative metabolic pathways to compensate for the action of the antibiotic and ensure the survival of the organism
45
What is the modified primary target for ampicillin resistance?
Transpeptidase
46
What is the action of B-lactamase enzymes?
To degrade the penicillin G inside the cell
47
How is the antibiotic prevented from reaching the target?
By reducing the permeability of the membrane or using efflux pumps to keep the drug outside the cell, as observed against ciprofloxacin for example
48
What is the action of a drug-resistant bacterial strain?
It can transfer the resistance gene to other strains of the same spp - or to individuals of a diff spp altogether - that have never been exposed to the drug in the first place
49
How can antibiotic resistance spread widely and compromise the whole antibiotic therapies?
Via the transfer of the resistance gene by a drug-resistant bacterial strain to other strains of same spp or to individuals of a diff spp altogether that are not exposed to the drug in the first place
50
What is the result of the accumulation of antibiotic resistance genes?
It leads to the creation of "superbugs"
51
What are superbugs?
These are bacterial strains that are immune to all but the most drastic treatments
52
What are the current strategies to overcome antibiotic resistance?
To discover new antibiotics w/ novel modes of actions or to use diff antibiotics in "cocktails" - presuming that a bacteria might survive facing 1, but not 2 or 3 antibiotics simultaneously
53
What is the importance of antibiotic resistance genes in the lab?
These are an important tool for genetic engineering to select for transformed cells
54
What are the characteristics of E. coli?
1) Rod-shaped bacterium 2) Commonly found in the lower intestine of warm-blooded organisms addition: they are gram (-), anaerobic, and coliform bacteria of genus Escherichia
55
Can most E. coli strains cause harm?
No, most E. coli strains are harmless
56
Can some serotypes of E. coli cause serious food poisoning in their hosts, and are occasionally responsible for product recalls due to food contamination?
Yes Serotypes are: 1) Enterohemorrhagic (EHEC) 2) Enteroinvasive (EIEC) 3) Enteropathogenic (EPEC) 4) Enterotoxigenic (ETEC) 5) Enteroaggregative (EAEC)
57
What are the actions of some serotypes of E. coli strains?
1) It can cause serious food poisoning in their hosts | 2) They are occasionally responsible for product recalls due to food contamination
58
Are the harmless strains of E. coli part of the normal flora of the gut?
Yes
59
Can the harmless strains of E. coli produce vitamin K2 for their hosts? If yes, what is its effect? If not, what is its effect?
Yes, these strains produce vitamin K2 w/c can produce benefits to their hosts
60
What are the actions of the harmless E. coli strains?
1) To produce vitamin K2 | 2) To prevent colonization of the intestine w/ pathogenic bacteria
61
Can E. coli be grown and cultured easily and inexpensively in a lab setting?
Yes
62
Is E. coli considered as one of the best-studied model organisms? If yes, why? If no, why not?
Yes, because E. coli can be grown and cultured easily and inexpensively in a lab setting
63
What are the important spp of bacteria in the fields of biotechnology and microbiology?
E. coli
64
What is the purpose of E. coli in the fields of biotechnology and microbiology?
E. coli serves as the host organism for the majority of work w/ recombinant DNA
65
What is the generation time of E. coli under favorable conditions?
Only 20 mins

Clinical Bacteriology (Laboratory) (24 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions