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BIMM 120 > Chapter 5 > Flashcards

Chapter 5 Flashcards

1
Q

What is bacterial growth

A

Refers to the increase in the number of cells in a population. ex. growth of bacteria in something such as a food or tissue

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2
Q

What is binary fission

A

Cell division following enlargement of a bacterial cell to twice its starting size. It produces two identical daughter cells, each daughter cell receives a chromosome and sufficient copiues of all other cell constituents to exist as an independent cell

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3
Q

What is generation time

A

Time required for microbial cells to double in number

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4
Q

What is the septum

A

The point of division in an elongated cell to two daughter cells. There are changes in the cell wall

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5
Q

What re FTS (Filamentous temperature-sensitive) proteins

A

The name comes from genetic experiments and they are essential for cell division in prokaryotes. They interact with one another to form the divisome (cell division apparatus)

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6
Q

What are the FTS proteins and what do they do

A

FtsZ: forms ring around the center of cell, related to tubulin
ZipA: anchor that connects the FtsZ ring to cytoplasmic membrane
FtsA: helps connected FtsZ ring to membrane and also recruits other divisome proteins, related to actin

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7
Q

In bacterial cell division when does the DNA replicate

A

Before the FtsZ ring forms

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8
Q

What facilitates the location of the FtsZ ring

A

Min proteins find the middle of the cell

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9
Q

What is the FtsK protein

A

It mediates the separation of chromosomes to daughter cells, makes sure that each daughter cell gets a chromosome

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10
Q

What recruits the FtsZ ring to the middle of the cell

A

Min proteins?

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11
Q

What is MreB protein

A

Major shape determining protein in prokaryotes. FOrms cytoskeleton, spiral-shaped bands around the inside of cell, underneath the cytoplasmic membrane. Not found in coccus bactiera, and localized synthesis of new peptidoglcan to specific locations along the cylinder of a rod-shaped cell during growth

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12
Q

How do cell walls grow in cocci

A

Cell walls grow in opposite directions outward from the FtsZ ring

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13
Q

How do cell walls grow in rod-shaped cells

A

Growth occurs at several points along length of the cell

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14
Q

How is new petidoglycan synthesized

A

Preexisting peptidoglycan needs to be partially severed to allow new synthesis. Beginning at the FtsZ ring, smalle openings in the wall are created by autolysins (enzymes). New cell wall material is added across the opening.

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15
Q

What happens when there is too much autolysin

A

Too much autolysin activity causes cells to lyse

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16
Q

What are wall bands

A

The junction between new and old peptidolycan

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17
Q

What is bactoprenol

A

A carrier molecule that plays major role in export and insertion of peptidoglycan precursors

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18
Q

What is transglycosylase

A

Enzyme that interacts with bactoprenol and forms sugar backbone. Inserts cell wall precurors into growing points of cell wall and catalyzes a glycosidic bond formation

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19
Q

How does the peptidoglycan process work

A

First the autolysin activity makes a cleavage in the backbone. Enzyme in the cell will make the precursor MG with pentapeptide and bactoprenol helps flip it up into the cell. Transglycosylase activity stitches that flipped segment into the cell wall

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20
Q

What is transpeptidation

A

The final step in cell wall synthesis. Forms the peptide cross-links and can be inhibited by the antibiotic penicillin. Defects in cross-links causes growing cells to lyse

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21
Q

Why doesnt penicillin work on non-growing cells

A

Only growing cells will lyse because penicillin blocks this growth activity, if the cell isnt growing then the peptidoglycan does not become weaken

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22
Q

What does generation time depend on

A

It depends on growth medium and incubation conditions: temperature, pH, nutrients available. Good conditions allow faster growth

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23
Q

What is Exponential growth

A

Log phase growth, cell numbers double within a specific time interval over several generations. Increase in cell numbers is a geomtric progression of the number 2

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24
Q

What is the equation for exponential growth

A

N=(N0)(2^n)
N = final cell number
N0 = initial cell number
n = number of generations during the period of exponential growth

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25
What is the equation for generation time
g=t/n g = generation time t = the duration of exponential growth n = number of generations during the period of exponential growth
26
What is a batch culture
A closed-system microbial culture of fixed volume. Something in a tube, a closed system where you have a certain amount of nutrients to begin with and a certain number of bacteria in the beginning
27
What are the 4 phases of a typical growth curve for a closed system
1. Lag Phase 2. Exponential Phase 3. Stationary Phase 4. Death Phase
28
Describe the lag phase
Interval between when a culture is inoculated and when growth begins. Cells are making enzymes and adjusting to the growth medium and conditions such as temperature
29
Describe the exponential/log phase
Rapid growth, healthiest state
30
Describe the stationary phase
The net growth rate of population is zero. Either an essential nutrient is being used up or waste products are accumulating and inhibiting growth, or both
31
Describe the death phase
The lack of nutrients and build up of waste products leads to net death of cells. Cells begin to die.
32
What is a continuous culture
An open-system microbial culture of fixed volume. New nutrients are entering and waste products are being removed
33
What is a chemostat
Most common type of continuous culture. Growth rate and population density of culture can be controlled. Constnatly supplies fresh nutrients nad washes away waste products
34
What is the dilution rate
Rate at which fresh medium is pumped in and spent medium leaves, determines growth rate. Concentration of a limiting nutrient determines cell density. Rich medium = high cell density. Poor medium = low cell density
35
What leaves the chemostat
Cells can leave the system, ones that they want to collect and obtain something from them that they are making
36
What are some limitations of microscopic cell counts
Can't distinguish between live and dead cells without special stains, phase-contrast microscope is required if stain is not used, staining takes time, motile cells need to be immobilized, debris in sample can be mistaken for cells
37
What is a Petroff-Hausser counting chamber
Allows cells to be counted in squares to determine an average number of cells
38
What is a flow cytometer
It uses laser beams, fluorescent dyes, and electronics, allows large number of cells to be counted quickly but the machines are relatively expensive.
39
What are viable cell counts
Measurement of living, reproducing population. After incubation for 1 day, colonies of cells are counted because it is assumed that each colony came form one cell
40
What are the two main ways to perform plate counts
Spread-plate method and Pour-plate method
41
To obtain accurate colony numbers samples much be diluted between what two values
Between 30 and 300 colonies per plate
42
Describe the spread=plate method
Sample is pipptted oto the surface of plate. Sample is spread evenly over surface and incubated. Cells are counted afterwards
43
Describe the pour-plate method
Sample is pipetted into sterile plate. Sterile medium is then added and mixed well with inoculum. It is allowed to solidify then incubated. Cells are counter afterwards (surface and subsurface colonies)
44
In what units are viable cell counts reported in
colony forming units CFU
45
What is the Great Plate Anomaly
Direct microscopic counts of natural samples reveal far more organisms are present than those recoverable on plates
46
Why does the Great Plate Anomlay exist
Microscopic methods count dead cells whereas viable counts do not. Different organisms may have vastly different requires for growth so a particular medium and incubation conditions are only good for some organisms. And we don't know how to grow all the different kinds of bacteria in the lab
47
What is the turbidity measurements for microbial growht
Turbidity measurements are an indirect, rapid, and useful method for measuring microbial growth. A spectrophometer is used to measure optical density
48
What is optical density
Measuring the amount of light that fails to pass through the solution (hits a cell). NOT the light absorbed
49
What results in higher OD values
More cells due to more light scattering
50
What is an abiotic factor in the environment
A factor that is not living: temperature, pH, media
51
What are cardinal temperatures
The minimum, optimum, and maximum teamperatures at which an organism grows
52
What is the minimum growth temperature
The minimum temperature is the temperature that is so cold the enzyme don't work so growth is unable to take place
53
What is the optimum growth temperature
The optimum temperature is the temperature at which enzymatic reactions are occurring at the maximal possible rate
54
What is the maximum growth temperature
The maximum growth temperature si the temperature at which the proteins denature and the enzymes won't work any more
55
What is a psychrophile
Grows best at cold temperatures (4C)
56
What is a mesophile
Grows best at normal/room temperature(20C-40C)
57
What is a thermophile
Grows best at hot temperatures (45C=80C)
58
What is a hyperthermophile
Grows best at temperatures hotter than that of thermophiles (Above 80C) Inhabit boiling hot springs and seafloor hydrothermal vents that can be in excess of 100C
59
What are extremophiles
Organisms that have evolved to grow under very hot or very cold conditions
60
What are psychrotolerants
Organisms that can grow at 0C but have an optimum growth temperature of 20C to 40C
61
What are the molecular adaptations of psychrophily
Evolution of enzymes and transport proteins taht function optimally in the cold. Cytoplasmic membranes have high UNSATURATED fatty acid contect
62
Describe membranes with high unsaturated fatty acid content
Unsaturated fatty acids have multiple double bonds, which causes kinks, and results in less-stable hydrophobic interactions and a more fluid membrane
63
How does microbial life compare growing at different temperatures
Prokaryotes grow at higher temperatures than eukaryotes, organisms with the highest temperature optima are Archaea, and nonphototropic organisms can grow at higher temperatures than phototrophic organisms
64
Why do nonphototropic organisms grow at higher temperatures than phototrophic organisms
There is much more membrane involved in photosynthesis due to generating the hydrogen charge across the memrbane and generating this charge could be problematic at higher temperatures
65
What are the molecular adaptations to thermophily
Enzymes and proteins evolved to function optimally at high temperatures. Bacteria have lipids rich in saturated fatty acids and Archaea have lipid monolayer rather than bilyar (more stable and less fluid)
66
Describe membranes with high saturated fatty acid content
Saturated fatty acids have only single bonds, no kinks, and causes the membrane to be less fluid and more stable
67
What is an example of a hyperthermophile enzyme used in industry
Taq DNA polymerase is used to automate the repetitive steps in PCR because the enzyme is stable at the near-boiling temperatures required to melt DNA strains (75 C to 80C)
68
What are neutrophiles
Organisms that grow best between ph 6 and pH 8
69
What are acidophiles
Organisms that grow best at low pH, acidic environments
70
What are alkaliphiles
Organisms that grow best at high pH, alkaline environments
71
What are the osmotic effects of an organism growing in fresh water
In fresh water, the cytoplasm has a higher solute concentration than the surrounding environment, thus water moves into the cell (positive water balance)
72
What are the osmotic effects of an organism growing in salt water
In salt water, the external solute concentration is higher, then water will flow out of the cell. Can be prevented by the accumulation of high concentration of small molecules (osmolytes) in the cell
73
What are halotolerants
Organisms that can survive under salty conditions
74
What are halophiles
Organisms that can't grow in freshwater, require a salty environment to thrive (3% NaCl)
75
What are extreme halophiles
Organisms that can grow in saturated salty environments
76
What are osmophiles
Organisms that live in environments high in sugar as the solute (as opposed to salt), can take advantage of the nutrients available
77
What are xerophiles
Organisms that are able to grow in very dry environments, they put down a thick capsule or slime layer around the cell to keep themselves from drying out between periods of rain
78
What are aerobes
Organisms that require oxygen to live
79
What are anaerobes
Organisms that do not require oxygen to live and may be killed by exposure to oxygen
80
What are faculative organisms
Organisms that can live with or without oxygen
81
What are aerotolerant anaerobes
Organisms that can tolerate oxygen and grow in its presence even though they cannot use it
82
What are microaerophiles
Organisms that can use oxygen only when it is present at low levels
83
When growing anaerobic microorganisms what are reducing agents
Chemicals added to culture media to reduce oxygen

BIMM 120 (17 decks)

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