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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
Q

What is the equation for generation time

A

g=t/n
g = generation time
t = the duration of exponential growth
n = number of generations during the period of exponential growth

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26
Q

What is a batch culture

A

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

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27
Q

What are the 4 phases of a typical growth curve for a closed system

A
  1. Lag Phase
  2. Exponential Phase
  3. Stationary Phase
  4. Death Phase
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28
Q

Describe the lag phase

A

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

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29
Q

Describe the exponential/log phase

A

Rapid growth, healthiest state

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30
Q

Describe the stationary phase

A

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

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31
Q

Describe the death phase

A

The lack of nutrients and build up of waste products leads to net death of cells. Cells begin to die.

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32
Q

What is a continuous culture

A

An open-system microbial culture of fixed volume. New nutrients are entering and waste products are being removed

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33
Q

What is a chemostat

A

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

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34
Q

What is the dilution rate

A

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
Q

What leaves the chemostat

A

Cells can leave the system, ones that they want to collect and obtain something from them that they are making

36
Q

What are some limitations of microscopic cell counts

A

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
Q

What is a Petroff-Hausser counting chamber

A

Allows cells to be counted in squares to determine an average number of cells

38
Q

What is a flow cytometer

A

It uses laser beams, fluorescent dyes, and electronics, allows large number of cells to be counted quickly but the machines are relatively expensive.

39
Q

What are viable cell counts

A

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
Q

What are the two main ways to perform plate counts

A

Spread-plate method and Pour-plate method

41
Q

To obtain accurate colony numbers samples much be diluted between what two values

A

Between 30 and 300 colonies per plate

42
Q

Describe the spread=plate method

A

Sample is pipptted oto the surface of plate. Sample is spread evenly over surface and incubated. Cells are counted afterwards

43
Q

Describe the pour-plate method

A

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
Q

In what units are viable cell counts reported in

A

colony forming units CFU

45
Q

What is the Great Plate Anomaly

A

Direct microscopic counts of natural samples reveal far more organisms are present than those recoverable on plates

46
Q

Why does the Great Plate Anomlay exist

A

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
Q

What is the turbidity measurements for microbial growht

A

Turbidity measurements are an indirect, rapid, and useful method for measuring microbial growth. A spectrophometer is used to measure optical density

48
Q

What is optical density

A

Measuring the amount of light that fails to pass through the solution (hits a cell). NOT the light absorbed

49
Q

What results in higher OD values

A

More cells due to more light scattering

50
Q

What is an abiotic factor in the environment

A

A factor that is not living: temperature, pH, media

51
Q

What are cardinal temperatures

A

The minimum, optimum, and maximum teamperatures at which an organism grows

52
Q

What is the minimum growth temperature

A

The minimum temperature is the temperature that is so cold the enzyme don’t work so growth is unable to take place

53
Q

What is the optimum growth temperature

A

The optimum temperature is the temperature at which enzymatic reactions are occurring at the maximal possible rate

54
Q

What is the maximum growth temperature

A

The maximum growth temperature si the temperature at which the proteins denature and the enzymes won’t work any more

55
Q

What is a psychrophile

A

Grows best at cold temperatures (4C)

56
Q

What is a mesophile

A

Grows best at normal/room temperature(20C-40C)

57
Q

What is a thermophile

A

Grows best at hot temperatures (45C=80C)

58
Q

What is a hyperthermophile

A

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
Q

What are extremophiles

A

Organisms that have evolved to grow under very hot or very cold conditions

60
Q

What are psychrotolerants

A

Organisms that can grow at 0C but have an optimum growth temperature of 20C to 40C

61
Q

What are the molecular adaptations of psychrophily

A

Evolution of enzymes and transport proteins taht function optimally in the cold. Cytoplasmic membranes have high UNSATURATED fatty acid contect

62
Q

Describe membranes with high unsaturated fatty acid content

A

Unsaturated fatty acids have multiple double bonds, which causes kinks, and results in less-stable hydrophobic interactions and a more fluid membrane

63
Q

How does microbial life compare growing at different temperatures

A

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
Q

Why do nonphototropic organisms grow at higher temperatures than phototrophic organisms

A

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
Q

What are the molecular adaptations to thermophily

A

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
Q

Describe membranes with high saturated fatty acid content

A

Saturated fatty acids have only single bonds, no kinks, and causes the membrane to be less fluid and more stable

67
Q

What is an example of a hyperthermophile enzyme used in industry

A

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
Q

What are neutrophiles

A

Organisms that grow best between ph 6 and pH 8

69
Q

What are acidophiles

A

Organisms that grow best at low pH, acidic environments

70
Q

What are alkaliphiles

A

Organisms that grow best at high pH, alkaline environments

71
Q

What are the osmotic effects of an organism growing in fresh water

A

In fresh water, the cytoplasm has a higher solute concentration than the surrounding environment, thus water moves into the cell (positive water balance)

72
Q

What are the osmotic effects of an organism growing in salt water

A

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
Q

What are halotolerants

A

Organisms that can survive under salty conditions

74
Q

What are halophiles

A

Organisms that can’t grow in freshwater, require a salty environment to thrive (3% NaCl)

75
Q

What are extreme halophiles

A

Organisms that can grow in saturated salty environments

76
Q

What are osmophiles

A

Organisms that live in environments high in sugar as the solute (as opposed to salt), can take advantage of the nutrients available

77
Q

What are xerophiles

A

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
Q

What are aerobes

A

Organisms that require oxygen to live

79
Q

What are anaerobes

A

Organisms that do not require oxygen to live and may be killed by exposure to oxygen

80
Q

What are faculative organisms

A

Organisms that can live with or without oxygen

81
Q

What are aerotolerant anaerobes

A

Organisms that can tolerate oxygen and grow in its presence even though they cannot use it

82
Q

What are microaerophiles

A

Organisms that can use oxygen only when it is present at low levels

83
Q

When growing anaerobic microorganisms what are reducing agents

A

Chemicals added to culture media to reduce oxygen

BIMM 120 (17 decks)

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