Microbial Growth Flashcards
1
Q
Which elements are essential for microorganisms? (7)
A
H, C, N, O, P, S, Se
2
Q
What needs to be done before the incorporation of most nutrients into cellular material?
A
Slight modification
3
Q
___ are required in large amounts. Ex.
A
Macronutrients. Ex: Carbo, nitrogen, hydrogen, oxygen, phosphorous, sulfur, potassium, magnesium, calcium, sodium.
4
Q
___ are required in trace amounts. Ex.
A
Micronutrients. Ex: iron, manganese, cobalt, copper.
5
Q
What are growth factors?
A
Vitamins, amino acids, purines, pyrimidines and other organic molecules that the microorganism needs for growth but can’t synthesise by itself.
6
Q
Can by-product or waste of microorganism be growth factors?
A
Yes
7
Q
Example of growth factors.
A
Vitamin K, Biotin, p-amino benzoic acid, folic acid, riboflavin, lipoid acid, thiamine.
8
Q
What is the growth of the population?
A
The increase number of cells or biomass
9
Q
How do most prokaryotes multiply?
A
Binary fission
10
Q
What are the 3 steps of binary fission?
A
- Cell elongation
- Septum formation
- Completion of septum, formation of walls, cell separation.
11
Q
What does each daughter cell receive to exist ad an independent cell?
A
The cell receives:
- one copy of the chromosome
- ribosomes
- macromolecules
- other molecules
12
Q
What is the generation time of e.coli?
A
20 minutes
13
Q
What does cell division require?
A
It requires:
- synthesis of the news cell wall material
- its destruction by autolysins
14
Q
What allows peptidoglycan subunit to be exported across the cytoplasmic membrane?
A
Bactoprenol
15
Q
Where do autolysins create some gaps in the peptidoglycan? What does this allow?
A
- At the division ring (FtsZ ring)
- this allows the rearrangement of the peptidoglycan and synthesis of the new cell wall.
16
Q
What are wall bands?
A
Scars between old and new peptidoglycan?
17
Q
What type of medium is MacConkey medium?
A
Selective
18
Q
Bile salts inhibit growth of ___ and are permissive for ___/___ pathogens
A
- gram +
- gram - / enteric
19
Q
It differentiates between lactose ___ (pink) and lactose ___ (colourless)
A
- fermenters
- non-fermenters
20
Q
With bile precipitate, E. coli forms ___ colonies.
It is lactose ___ .
A
- dark pink
- positive
21
Q
What coloraturas are lactose negative?
A
colourless
22
Q
Lactose -> __ + __
A
glucose + galactose
23
Q
Glucose –> ___ –> ___(lactic acid, reduce pH)
A
- glycolytic pathway
- fermentation: lactate
24
Q
Mannitol Salt is a ___ medium.
A
selective
25
Which medium is used for isolation or detection of Staphylococcus?
Mannitol-salt
26
What inhibits most gram negative and many gram positive in the selective media (Mannitol-salt)?
High NaCl concentration.
27
Example of a mannitol fermenter (mannitol +)
| What color is it?
- Staphylococcus aurea.
| - Yellow
28
+ mannitol fermenters : __
| - mannitol fermenters : __
- yellow
| - pink
29
Example of negative mannitol fermenter.
Staphylococcus epidermidis
30
Why count bacteria growth?
- to evaluate contamination of food, water
- to ensure enough microorganisms are inoculated (ex; beer, wine, yogurt, cheese)
- to evaluate the efficiency of antimicrobial agents
- to study microbial populations from different ecosystems.
- to measure effect of mutation of gens involved in metabolic pathway, survival, protection, virulence, etc
31
Results are reliable when how many colonies?
Between 30 - 300
32
What type of growth medium is required to enumerate bacteria?
A permissive growth medium.
33
What are 2 methods to enumerate bacteria?
- the spread-plate method
| - the pour plate method
34
Steps of spread-plate method.
- sample is pipetted onto surface of agar plate
- sample is spread evenly over surface of agar using a sterile glass spreader
- incubation time
35
Steps of pour-plate method.
- sample is pipetted into sterile plate
- sterile medium is added and mixed well with inoculum
- solidification and incubation
36
What can be made to get a viable count of bacterial cultures that can reach billions of cells.
A serial dilution.
37
What can affect the results of a serial dilution?
The skills of the technician.
38
What is the CFU formula?
CFU= (number of colonies)/ (dilution plated x volume plated)
39
What can be used to differentiate dead and live cells in the lab?
Viability staining.
40
During microscopic counts what is counted? (3)
- dead cells
- alive cells
- cells that can't be grown in lab
41
In viability staining, dead cells are ___ and live cells are ___.
- dead : red
| - alive : green
42
What are the pros of viability staining?
- fast
| - no need to wait until bacteria has grown
43
What are the cons of viability staining?
- small cells can be missed
| - motile cells are hard to count and must be immobilised
44
Microscopic counts are done on what?
| What does it consist of?
- A counting chamber.
| - consists of a whole grid with 25 large squares. 1 large square has 16 small squares..
45
What is used to count during viability staining (large/small squares)?
several large squares are counted and the number is averaged.
46
Formula used when doing microscopic counts.
number of cells in a large square x 25 large squares x 50 x 10^3
47
What is better at counting big cells such as protozoan, yeast, mammalian cells?
Flow cytometry.
48
What can flow cytometry be used for?
- to sort cells according to size, shape, labelling
49
What occurs in flow cytometry.
1. Sample enters the nozzle. sample = stained cells in suspension
2. Hydrodynamic Focusing.
Cells pass through in 'single file'
3. Laser light source.
Allows the detection of fluorescent dyes. When stained cells : fluorescence emitted.
50
What does the detection of fluorescent dyes allow?
Allows labelling of specific cell types or species.
51
For flow cytometry where are black dots are seen during :
- dead control
- live control
- test
- dead control : dead cells are signalled with many black dots
- live control : live cells have black dots
- test : dots are equivalent for Iive and dead cells
52
What does the turbidimetric method measure?
It measures the contribution of both living and dead cells to turbidity.
53
In the turbidimetric method what is affected by properties of cells (clumping, size...)
OD (optical density)
54
Optical density is high when water is the most or least turbid?
Most turbid.
55
What needs to be established? (2)
- A standard curve must be made
| - relationship between OD and cell number
56
Time needed for the population to double =
Generation time
57
What does the generation time depend on? (2)
- the growth medium
| - the conditions
58
When conditions are right, microorganisms grow ___ .
| The population ___ at a ___ rate.
- exponentially
- doubles
- constant
59
Formula to calculate the number of cells (N).
N= (number of cells initially) x (2^number of generation)
60
Difference between a logarithmic and arithmetic curve.
logarithmic : straight curve
| arithmetic : exponential
61
How to calculate the generation time (g)?
g= t/n
t-time
n-number of generation
g-generation time
62
What is the form of a generation curve?
Straight line, increases.
63
What are the 4 growth phases in a batch culture?
- Lag
- Exponential
- Stationary
- Death
64
Which has a more viable organisms in the stationary phase (viable count or turbidity count)?
Viable count
65
Time needed by the bacteria to adjust to new condition is the __ phase.
Lag
66
The growth in the lag phase is __.
Slow
67
Doubling of the population at a constant rate is in the ___ phase.
Exponential.
68
What occurs in the stationary phase? (4)
- limiting nutrients are depleted or accumulation of product inhibits growth
- growth is stopped
- no net increase in cell number
- induction of "survival" systems.
69
Are cells still metabolically active in the stationary phase?
Yes
70
Cells start to die, metabolism has stopped and some cases cell death occurs with cell lysis in the __ phase.
Death.
71
What type of function is the death phase?
Exponential.
72
What type of culture is continually being affected by the metabolic activities of the growing microorganism (depletion of nutrients, generation of toxic waste)?
Batch cultures.
73
Most natural environments are __ systems.
Open
74
What do open systems experience? (4)
- constant supply of nutrients and diffusion of waste
- competition with other microorganism
- predation (protozoan, worms)
- changing environmental conditions
75
What to most environment systems reach over time?
An equilibrium
76
What is an equilibrium?
A division rate= death rate
77
What is the main factor of a limiting growth factor?
the concentration
78
What can be used in the lab to keep microorganisms in a CONSTANT growth rate over a long period of time?
Chemostats
79
Describe a chemostat.
1. Fresh medium (supply of limiting nutrients) from reservoir passes through flow-rate regulator.
2. Fresh medium enters the gaseous headspace of the cultural vessel.
3. The overflow of medium escapes, it contains dead microbial cells.
80
What happens when equilibrium is reached? (2)
- The number of cells is constant
| - the growth rate = death rate
81
Fact about concentration of a limiting nutrient
- fresh medium
| - aeration
82
Facts about dilution rate
- addition of fresh medium
| - washout
83
What affects growth in nature? (7)
- nutrients
- temperature
- pH
- osmolarity
- oxygen
- pressure
- radiation (visible light, UV light)
84
Microorganisms that grow preferentially under extreme conditions are __
Extremophiles
85
__ % of microbial species have never been grown as a pure culture in the laboratory.
99
86
What does minimum temperature cause?
- membrane gelling
| - growth can't occur because transport processes are slow
87
What does maximum temperature cause?
- protein denaturation
- collapse of the cytoplasmic membrane
- thermal lysis
88
What does optimum temperature cause?
- enzymatic reactions occur at maximum possible rate
89
Organisms that can grow at 0°C but have optima around 20 to 40 °C are called __
psychrotolerant
90
Organisms that have optima at :
- 4°C are ___
- 39°C are ___
- 60°C are ___
- 88°C & 106°C are ___
- psychrophile
- mesophile
- thermophile
- hyperthermophile
91
Escherichia coli is __
Mesophile
92
What kills micro-organisms?
Ice crystals (cold temperature doesn't kill them)
93
Microbial cultures are preserves at -80°C or -196°C in __.
Liquid nitrogen
94
How do microbes adapt to cold temperatures?
- change in protein structure and sequence so enzyme can be active
- transport across the membrane is optimal
- cytoplasmic membrane is modifies to stay fluid
- cold-shock proteins help keep proteins active.
95
What are antifreeze proteins (glycerol) that help the formation of ice crystals that can puncture the cytoplasmic membrane?
Cryoprotectants
96
What grows best at high pressure?
Barophilic (piezophilic)
97
characteristics of a hydrothermal vent (2)
- high temp
| - high pressure
98
What can heat-stable enzymes be useful for?
| Example
- biotechnology
| - tas polymerase
99
What helps resist high temperatures but aren't metabolically active?
Endospores
100
How does microbial life adapt at high temperature?
- change in protein sequence so enzymes aren't denatured
- transport across the membrane functions optimally
- modification of cytoplasmic membrane so it remains stable
- heat shock proteins keep proteins in active conformation
- DNA stabilise by projection mechanisms
101
Enzymes at high temperature are ___
heat-stable
102
What are :
- alkaliphiles
- acidophiles
- neutrophiles
- pH >= 8
- ph <= 5.5
- ph > 5.5 and <8
103
What happens at low pH?
Low pH : cytoplasmic modification require high concentration of protons.
104
What happens at high pH
High pH : cytoplasmic modification because low composition of protons, sodium-dependent pumps used for transport and motility
105
Microorganisms that can grow at high salt concentrations are called ___
What do they usually require for growth?
- halophiles
| - NaCl
106
Example of nonhalophiles
E. coli
107
Difference between obligate and facultative aerobes?
Obligate - require O2
| Facultative - don't require O2 but grows better with it
108
What indication is used to differentiate toxic and anoxic zones?
Redox indicator reazurin
109
Composition of tubes for
- obligate aerobes
- anaerobes
- facultative aerobes
- microaerophiles
- aerotolerant anaerobes
oxic zone - anoxic zone
1. a lot of microorganisms - none
2. no microorganisms - microorganisms mainly at bottom of tube
3. most microorganisms -microorganisms homogeneously present
4. few microorganisms in both phases
5. many microorganisms homogeneously in both phases
110
During oxygenic photosynthesis, __ is oxidised to __
H2O -> O2
111
During aerobic respiration and oxygenic photosynthesis, what is produced?
toxic forms of oxygen
112
Aerobes and facultative aerobes usually have __ and __
catalase; superoxide dismutase
113
If anaerobes have the same enzymes a aerobes they are __.
aerotolerant anaerobes (they can grow in presence of oxygen).
