Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Microbioloy > Microbial growth > Flashcards

Microbial growth Flashcards

1
Q

name an example of a bacteria that does not have a circular chromosome

A

Borrelia burgdorferi the cause of lime disease has a linear chromosome

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

What is the most common method of replication of bacteria

A

Binary fission

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

what happens in binary fission

A

the cell grows and increases cellular components
DNA replication begins on a location on the circular chromosome (origin of replication)
replication continues in opposite directions along the chromosome until terminus is reached
the center constricts until two daughter cells are formed

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

what is cytokinesis

A

division of cytoplasm

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

what directs the process of cytokinesis and cell division

A

The protein FtsZ

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

What does FtsZ protein do

A

assembles into a Z ring on the cytoplasmic membrane

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

what anchors the Z ring

A

FtsZ-binding proteins and defines the division plane between the two daughter cells

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

what does divisive do

A

activates to produce a peptidoglycan cell wall and build a septum that divides the two daughter cells

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

What is generation time

A

the time between the same points of the life cycle in two successive generations

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

what is another term for generation time in prokaryptes

A

doubling time

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

what is doubling time

A

the time it takes for the population to double through one round of binary fission

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

how fast can E. coli double

A

in 20 minutes under optimal conditions

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

What is the generation time of mycobacterium tuberculosis

A

between 15 and 20 hours

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

what is the generation time of M. leprae (Hansons disease)

A

14 days

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

What is a closed culture

A

when no nutrients are added and most waste is not removed

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

what is a growth curve

A

reproductive growth pattern of microorganisms in a closed culture

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

What is culture density

A

the number of cells per unit volume,

in a closed environment it is also the number of cells in a population

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

What is an inoculum

A

the beginning of the growth curve representing a small number of cells that are added to a fresh culture medium

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

what is the lag phase

A

the initial phase of the growth curve where cells are gearing up for the next phase of growth

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

what happens to cells during the lag phase

A

they do not change in number but do grow larger and are metabolically active synthesizing proteins needed to grow

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

what happens to cells that are damage while being transferred to a medium

A

they are repaired during the lag phase

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

what determines the duration of the lag phase

A

species and genetic make of cells, composition of the medium and size of the original inoculum

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

What happens during the log phase

A

the cells are actively dividing by binary fission and their number increases exponentially

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

what is intrinsic growth rate

A

the genetically determined generation time under specific conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Why are cells in the log phase used for industrial application
there is constant growth rate and uniform metabolic activity
26
what contributes to the slowing of the growth rate
waste products accumulating, nutrients being used up, depletion of oxygen
27
what is the stationary phase
the total number of live cells that reach a plateau
28
what is the relationship of cell numbers during the stationary phase
the number of cells creased is equal to the number of cells dying
29
What happens to cells during the stationary phase
they switch to survival mode of metabolism, synthesis of peptidoglycan, proteins, and nucleic acids slow so they are more susceptible to antibiotics
30
when do cells undergo sporulation
stationary phase
31
when are are secondary metabolites including ABX synthesized
stationary phase
32
what happens during the death phase
toxic waste accumulates and nutrients are exhausted so cells begin to die.
33
why are persister cells important
they are associated with chronic infections such as TB
34
What is a chemostat
a culture vessel that allows nutrients to be added and waste to be removed and air to be controlled to maintain a logarithmic phase of growth
35
What is direct cell count
the counting of cells in a liquid culture or colonies on a plate to estimate how many organisms are present
36
what is the direct microscopic cell count
transferring a known volume of a culture to a calibrated slide and counting the cells under a microscope
37
what is the calibrated slide used for direct microscope cell count called
petrol-hausser chamber
38
what are the benefits of the chamber
it is easy to use, fast and inexpensive
39
what are the cons of the counting chamber
does not work well with dilute cultures because there may not be enough cells, can't always tell between live and dead cells
40
how does fluorescence staining help with counting cells
you can determine the viability of cells because it binds to nucleic acids, primary and secondary stains have different ability to cross cytoplasmic membrane
41
which fluoresces stain can penetrate the intact cytoplasmic membrane
the primary green stain
42
when can red, secondary stain enter a cell
if the cytoplasmic membrane is damage
43
What does a Coulter counter do
detects and counts the changes in electrical resistance in a saline solution
44
how does a Coulter counter work
a glass tube is immersed in an electrolyte solution the first electrode is suspended in the glass tube the second is is outside the tube, as the cells are drawn through the aperture they change resistance change represents a cell.
45
what happens if the culture in the Coulter counter is too concentrated
more than one cellmate pass through at a time skewing the results, does not differentiate between live and dead cells.
46
why is the viable plate count considered a low estimate of the actual number of cells,
multiple cells might form the same colony so a single colony might represent a single cell
47
how many colonies are typically on a plate
30-300
48
why is 30-300 the best range
too few is not statistically reliable , overcrowded makes it difficult to count accurately, it minimizes occurrences of more than one bacterial cell forming a single colony
49
What is the goal of serial dilution
to obtain plates with CFU,s between 30-300
50
what determines the number of serial dilutions
preliminary estimate of culture density
51
what are the steps of the our plate method
1. bacteria is mixed with warm agar 2. sample cured onto sterile plate 3. sample swirled to mix, allowed to solidify 4. plate incubated until bacterial colonies grow
52
what temperature should liquid warm agar be
45-50C
53
What are the tips of the spread plate method
1. sample is poured onto solid medium 2. spread the sample evenly over the surface 3. plate incubated until bacterial colonies grow on the surface of the medium
54
what is the membrane filtration technique
known volumes are vacuum-filtered aseptically through a membrane with a pore size small to trap microorganisms so they are more concentrated.
55
what is the most probable number method
a statistical procedure for estimating thenumbr of viable microorganisms in a sample usually for water and food samples
56
what does the most probable number evaluate
detectable growth by observing changes in turbidity or color due to metabolic activity
57
what is a typical application of th e most probable number method
estimation of coliform in a sample of pond water
58
what does the pretense of coliform a sign of
contamination by fecal mater
59
how does the MPN method work
three dilutions of the water sample is tested by inoculating five lactose broth tubes with 10ml of sample, 5 with 1ml and 5 with 0.1ml. the lactose tube the results are based of ph indicator
60
what is the most common method of indirect cell counts
measuring turbidity
61
what machine measures turbidity
spectrophotometer
62
how does a spectrophotometer work
a light beam is transmitted through a bacterial suspension, the amount of light passing through and reaching the detector is converted to a percent or value
63
what is the relationship between light detected and bacteria
the more bacteria the less light
64
how must the cell suspension for dry measuring be prepared
by concentrating through filtration or centrifugation, washed and then dried
65
what is dry weight measuring useful for
filamentous microorganisms that are difficult to enumerate by direct or viable plate count
66
What happens in fragmentation
many nucleotides may accumulate I an enlarged round cell or along a filament leading to many new cells at once that slit from a parent filament and float away
67
example of bacteria that uses fragmentation
cyanobacteria
68
where is fragmentation commonly observed
actinomycetes
69
what are actinomycetes
a group of gram positive anaerobic bacteria found in soil
70
how do epulopiscium divide
several daughter cells grow fully in the parent which eventually disintegrates releasing new cells
71
what happens in budding
species form a long narrow exertion at one pole, the tip of the extortion swells and forms a smaller cell, the bud detaches from the parent cell
72
where is budding most common
yeast, but also observed in prosthecate bacteria and one cyanobacteria
73
Where do filamentous biofilms form
rapidly flowing water, such as freshwater streams, eddies and specially designed lab flow cells that replicate fast moving liquid
74
what does the extracellular matrix of biofilm consist of
extracellular polymeric substances secreted by organisms in the biofilm
75
what percent of the biofilm is extracellular matrix
50-90% of total dry mass
76
what is app
a hydrated gel composed of polysaccharides and containing other macromolecules such as proteins, nucleic acids and lipids that help maintain integrity and function of the biofilm
77
what do channels in the EPS do
allow movement of nutrients wast and gases through biofilm
78
what are planktonic cells
free-floating microbial cells that live in an aquatic environment
79
what are the stages of biofilm formation
1. reversible attachment of planktonic cells 2. first colonizers become irreversibly attached 3. growth and cell division 4. production of EPS and formation of water channels 5. attachment of secondary colonizers and dispersion of microbes to new sites
80
what happens in biofilms that contain both aerobic and anaerobic pathogens
hate product of one organism becomes nutrients for another, aerobic microorganisms consume oxygen crating anaerobic regions that promote growth of anaerobes
81
what is quorum sensing
the mechanism that cells in a biofilm coordinate their activities in response to environmental stimuli
82
what does quorum sensing allow microorganisms to do
to detect their cell density through the release of binding of small diffusible molecules called autoinducers
83
what do autoinducers do
initiate a cascade of reactions that activate genes associated with cellular functions that are beneficial when population reaches critical density
84
how do gram-negative bacteria communicate
N-acylated homoserine lactones
85
how do gram-positive bacteria communicate
small peptides
86

Microbioloy (10 decks)

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