Microbiology! Flashcards
(141 cards)
1
Q
What are the three main techniques used for growing bacteria?
A
Slopes
Liquid Culture
Plates
2
Q
What are some advantages to being small?
A
Small cells have high surface area to volume ratio, allowing faster nutrient exchange per unit volume and faster reproduction.
3
Q
What did Robert Hooke do?
A
Wrote the first book devoted to microscopic observations
4
Q
What did Louis Pasteur do?
A
Showed heat could be used to ‘sterilise’
Disproved the idea of spontaneous generation
5
Q
What did Robert Koch do?
A
Showed microorganisms are often the cause of disease
Careful examination of blood from diseased animals showed the presence of bacteria
He used mice and anthrax to develop Koch’s postulates
6
Q
What are the four key steps in Koch’s postulates?
A
- The suspected pathogen must be present in all cases of the disease and absent from healthy animals
- The suspected pathogen must be grown in pure culture
- Cells from a pure culture of the suspected pathogen must cause disease in a healthy animal
- The suspected pathogen must be reisolated and shown to be the same as the original
7
Q
What are the three domains of life?
A
Prokarya
Archaea
Eukarya
8
Q
Name some types of microorganisms.
A
Bacteria Archaea Protozoa Algae Prions Viruses Fungi
9
Q
How many phyla of archaea are there?
A
2
10
Q
Why is classification of archaea difficult?
A
Majority have not been isolated in the laboratory
11
Q
Where do protozoa generally live?
A
In soil
Wet sand
Fresh and salt water
12
Q
Are protozoa prokaryotes or eukaryotes?
A
Eukaryotes
13
Q
Are protozoa unicellular or multicellular?
A
Unicellular
14
Q
Describe algae.
A
Eukaryotes
Contain chloroplasts
Have cell walls
Both terrestrial and aquatic
15
Q
What is an autotroph?
A
Use carbon dioxide as their carbon source
Primary producers
Synthesise new organic matter
16
Q
What is a heterotroph?
A
Use organic compounds as their carbon source
Either feed directly on other cells
Or live off products other organisms excrete
17
Q
What is a symbiotic/ mutualistic relationship?
A
Cooperative relationship with the host
18
Q
What is a parasitic relationship?
A
Antagonistic relationship with the host
19
Q
What does saprotrophic mean?
A
The host is dead
20
Q
What is phototrophy?
A
Obtaining energy from light
21
Q
What is photosynthesis?
A
Conversion of light to chemical energy
22
Q
What is the lower limit to cell size?
A
0.15 μm would only just fit in all the essential cellular components
23
Q
What are the two results you can get from a gram stain test?
A
Gram-positive and gram-negative
24
Q
What colour do gram-positive bacteria appear?
A
Purple
25
What colour do gram-negative bacteria appear?
Red/ pink
26
What is an endospore?
Highly differentiated cell produced by certain types of bacteria
Resistant to heat, harsh chemicals and radiation
Survival structures
27
When does sporulation occur and what happens?
An essential nutrient is exhausted like carbon or nitrogen
Vegetative cells stop growing
Endospore develops within cell and is released
28
What happens to an endospore when conditions are good and how long can an endospore remain dormant for?
Germinates into vegetative cell when conditions are good
| Spore can remain dormant for years
29
What are three endospore morphologies?
Terminal endospore
Subterminal endospore
Central endospore
30
Can endospores be stained using staining dyes?
They are impermeable to most dyes so usually seen as unstained regions within cells
31
What are the four key layers of an endospore?
Exosporium
Spore coat
Cortex
Core
32
What is the exosporium of an endospore?
Thin protein covering
33
What is the spore coat of an endospore?
Layers of spore specific proteins
34
What is the cortex of an endospore?
Loosely cross-linked peptidoglycan
35
What is the core of an endospore?
Core wall, cell membrane, cytoplasm, nucleoid, ribosomes, etc
36
What are fimbriae and pili?
Filamentous structures composed of protein extending from the surface of a cell
37
What is the purpose of fimbriae? What is the negative of this?
Enable cells to stick to surfaces and each other
| Can assist the disease process
38
How do pili differ from fimbriae?
Typically longer, and only one or two present
39
What are the two major functions of pili?
1. Conjugation: genetic exchange between cells
2. Adhesion of pathogens to specific host tissues for subsequent invasion
May also help with mobility
40
What are the two major types of bacterial cell movement?
Swimming
| Gliding
41
Why do microbial cells need to move under their own power?
Enable the cell to reach different parts of their environment
42
What do flagellum do?
The flagellum rotate to push or pull a cell through a liquid
43
What are three different types of attachments of flagella?
Polar flagellation
A tuft
Peritrichous flagellation
44
What is polar flagellation?
Flagella are attached to one or both ends
45
What is a tuft of flagella?
A group of flagella attached to one end of the cell
46
What is peritrichous flagellation?
Flagella inserted at many locations
47
What is the structure of flagella?
Helical
Wavelength characteristic for a given species
Composed of many copies of a protein called flagellin
Molecular motor embedded in cell membrane to drive movement of flagellin filament
48
How does the flagellum get energy for rotation?
Proton movement across membrane through Mot complex
Protons flow through channel
Exert electrostatic forces on helically arranged charges on rings
Attraction between charges causes rotation
49
Is gliding slower or faster than swimming with flagella?
Much slower
50
What is taxis?
Movement towards something that will aid growth or away from toxins
51
What is chemotaxis?
Response to chemicals
52
What is phototaxis?
Response to light
53
Describe myxobacteria.
Multicellular structures
Life cycles indicate intercellular communication
Form fruiting bodies- often striking colours and morphology
Glide- slime trails
54
How do bacterial cells glide?
With slimes and pili
55
What is chemotrophy?
Obtaining energy from chemicals
56
What do chemolithotrophs do?
Oxidation of inorganic compounds releases energy, stored at ATP
57
Are chemolithotrophs eukaryotes or prokaryotes?
Prokaryotes
58
Why is being a chemolithotroph a good metabolic strategy?
Competition is not an issue
Many of the inorganic compounds they use are waste products of chemoorganotrophs
Can live in association with chemooganotrophs
59
What do chemoorganotrophs do?
Oxidation of organic compounds to release energy
| Can be aerobic or anaerobic or both
60
What is nitrogen fixation?
Convert atmospheric nitrogen gas into a form that can be used by cells
No known eukaryotes can fix nitrogen
61
What are the two types of nitrogen fixing bacteria?
Free-living
| Symbiotic
62
Define free-living.
Require no host, they live free
63
Define symbiotic nitrogen fixing bacteria.
Can only exist in association with certain plants
| Live in root nodules
64
What is nitrification?
Oxidation of inorganic nitrogen compounds performed by nitrifying bacteria
65
Where are nitrifying bacteria mostly found?
In soils and water
66
Why is nitrification important for industry?
Plant productivity
| Sewage and wastewater treatment: Removing toxic amines and ammonia
67
What are the key cycles?
The Carbon Cycle
The Nitrogen Cycle
The Sulphur Cycle
68
What is humus?
Complex mixture of organic materials that have resisted rapid decomposition, derived primarily from plants and microorganisms
More carbon is bound in humus than in living organisms
69
Define growth for multicellular organisms.
Growth involves the whole organism getting bigger
70
Define growth for single celled organisms.
Growth is defined as an increase number of cells in a population
71
What is binary fission and which organisms replicate via this method?
One cells divides into two
Prokaryotes and some eukaryotes
All bacteria
72
What is generation time?
Time for one cell to split into two in binary fission
73
What is the generation time of E. coli in lab culture?
About 20 mins
74
How does generation time vary between lab cultures and cells in nature?
Cells grow much slower in nature where conditions are not optimised
Generation times of hours or days are more common
75
What does each daughter cell receive in binary fission?
```
A chromosome
Ribosomes
Macromolecular complexes like proteins
Monomers
Inorganic ions
```
76
Where does genetic variation come from in bacteria?
High mutation rate
Each new generation carries DNA with mutations compared to its parent and therefore has the power to evolve
Conjugation
77
What are the phases of the growth cycle?
Lag
Exponential
Stationary
Death
78
What is the lag phase?
Time between when culture is inoculated into fresh media and significant growth
79
What does the length of the lag phase depend on?
History of the inoculum
Nature of the medium
Growth conditions
80
What is the exponential phase?
Cell population doubles at regular intervals
81
What does the length of the exponential phase depend on?
Availability of environmental conditions: temperature, nutrients, etc
Genetic characteristic of the organisms
82
What is the healthiest cell state in the cell cycle?
Exponential phase
83
What happens in the stationary phase?
Essential nutrient in culture medium runs out
Organism's waste products build up to toxic levels
No net increase or decrease in cell numbers
Cell growth = cell death
84
What happens in the death phase?
Exponential decline of viable cells
| Rate of cell death typically faster than rate of growth
85
Describe batch culture.
Microbes cultured in an enclosed vessel
A 'closed' vessel
Typically flask or tube
Populations show a growth curve typical to that discussed so far
Environment is constantly changing due to nutrient consumption and waste production
86
Describe a continuous culture.
An 'open' system
Fresh medium added in
Culture medium (cells and waste) being removed
Rate of flow in = rate of flow out
Steady state: growth vessel reaches equilibrium
87
What can be controlled in a chemostat?
Growth rate
| Cell density
88
What is the dilution rate?
Rate fresh medium is added and spent medium is removed
89
What is the issue caused by the dilution rate of a continuous culture being too small?
Cells die from starvation
90
What is the issue caused by the dilution rate of a continuous culture being too high?
Cells can't grow fast enough and are washed out of the vessel
91
What is a microscopic count?
Count the number of cells present
| Samples dried onto slides or liquid samples
92
What are issues with microscopic counting?
Without special staining techniques, dead and live cells can't be distinguished
Imprecise
Small cells hard to see
Motile cells must be killed/ immobilised, debris may be mistaken for cells
93
What is a viable count?
A plate count
| Main assumption is each viable cell will divide to make one colony
94
What is a viable cell?
Able to divide and produce offspring
95
What are some issues of a viable count?
In mixed cultures, not all cells grow at same rate and colony sizes may vary so may miss small ones
Inaccurate pipetting, non-uniform sample, insufficient mixing, heat intolerance
96
What is a microenvironment?
Microorganisms are very small so only directly experience a tiny local environment
Numerous microenvironments can exist within a given habitat
97
What can we use to measure oxygen concentration in a soil particle?
Microelectrodes
98
How do organisms living in a soil particle differ from the inside to the outer layers?
Anaerboic organisms thrive near centre as microorganisms near outer edges consume all oxygen before it can diffuse to the centre
Aerobic organisms live in outer layers
99
What do mineral soils form from?
Weathering rock and inorganic materials
100
What do organic soils form from?
Sedimentation in bogs and marshes
101
Are most soils mineral or organic?
Most soils are a mixture of the two
| Mineral based soils predominate
102
What is groundwater?
Water in soils and rocks deep underground
103
Describe oxygenic phototrophs.
Include algae and cyanobacteria
Primary producers: energy comes from light
Often floating
Attached to bottom or sides of lake/ stream (benthic)
104
Describe the characteristics of coastal and ocean waters.
Very low nutrient levels, especially nitrogen, phosphorus and iron
Water temperatures are cooler and are more constant with seasons than freshwater
Overall microbial numbers are lower in marine compared to freshwater habitats
105
Describe the characteristics of freshwater.
Highly variable in resources and conditions
Both oxygen consuming and oxygen producing organisms present
The balance controls the cycle of nutrients
106
How are microbes in the ocean different to in other habitats?
Very small: typical characteristic of living in nutrient-poor environment because it requires less energy for cell maintenance
Require greater number of transport enzymes relative to cell volume to acquire nutrients from very dilute environment
107
Why are oceanic microbes important?
Oxygenic photosynthesis in the oceans is a major factor in controlling the Earth's carbon balance because the oceans are so large
108
What is the photic zone?
Where light can penetrate to in a body of water
109
What is the deep sea and how much of the ocean water is deep sea?
Deep sea is 1000m below sea level
| >75% ocean water is deep-sea water
110
Describe the characteristics of the deep sea.
Low temperature
High pressure
Low nutrients
111
What are hydrothermal vents?
Underwater hot volcanic springs
| Found 1000 m to greater than 4000 m deep
112
What are the abiotic growth factors?
```
Nutrient availability
Temperature
pH
Moisture
Oxygen
Pressure
Light
```
113
What is the minimum temperature for a species?
Growth isn't possible below this temperature
114
What is the optimum temperature for a species?
Growth is most rapid at this temperature
115
What is the maximum temperature for a species?
Growth isn't possible above this temperature
116
What pH range do most natural environments lie within?
4-9
117
What growth range of pH units do most microbes show?
2-3
118
What must intracellular pH remain relatively constant at?
Neutral, aside from extremophiles
119
What are two considerations in water availability?
1. Absolute water availability: how moist/dry it is
| 2. Osmotic potential: concentration of solutes such as salts/ sugars
120
What is water activity?
An expression of water availability
The ratio of the vapour pressure of the air in equilibrium with a substance or solution to the vapour pressure of pure water
How close a solution is to pure water
121
What does aerobic mean?
Grow at full oxygen tensions
| Respire oxygen
122
Define anaerobic.
Cannot respire oxygen
Obligate anaerobes are inhibited or even killed by oxygen
There are no anaerobic algae
123
Define facultative.
Under appropriate nutrient conditions will grow under either oxic or anoxic conditions
124
Define microaerophiles.
Aerobes than can only use oxygen when it is present at levels lower than air
125
Define aerotolerant.
Anaerobic but can tolerant oxygen
| However, they do not use oxygen in their metabolism
126
What is an extremophile?
An organism whose growth is dependent on extremes of temperature, salinity, pH, pressure or radiation, which are generally inhospitable to most forms of life
127
Describe a psychrophile.
Optimal growth temperature 15 degrees celsius or lower
Max growth temp 20 degrees celsius
Killed by warming, found in constantly cold environments
128
What does psychrotolerant mean?
Can grow at 0 degrees celsius
Optima is 20-40 degrees celsius
More widely distributed
Found in temperate climates, meat, dairy products, cider, vegetables and fruit at standard refrigeration temperatures
129
What is snow algae?
On the surface of permanent snow fields and glaciers
Pink discolouration
Red-pigmented spores
Germinate to form mobile green algal cells
130
What are some molecular adaptations to the cold?
Enzymes have optimal activities at low temperatures
Cytoplasmic membranes must remain functional: high content of unsaturated and shorter-chain fatty acids - so can stay in semifluid state at low temps
"Cold-shock" proteins
Cryoprotectants
131
What are "cold-shock" proteins?
Maintain other proteins activity and bind specific mRNAs to facilitate their translation at cold temps
Often in psychrophiles
132
What are cryoprotectants?
Solutes that help prevent the formation of ice-crystals in the cell
133
What is a thermophile?
Growth temp optimum greater than 45 degrees
Less extreme than hyperthermophiles
Found in range of habitats like the edges of hot springs
134
What is a hyperthermophile?
Growth temp optimum greater than 80 degrees
Found in hot springs
Only prokaryotes
Growth rates often quite high
135
Can prokaryotes or eukaryotes grow at higher temperatures?
Prokaryotes
136
What are some molecular adaptations to high temperatures?
Heat stable enzymes and proteins
More ionic bonds between amino acids
Highly hydrophobic interiors
Make a protein more resistant to unfolding
Increased DNA stability- increase cellular compatible solute levels to prevent chemical damage to DNA
Reverse DNA gyrase
137
What are acidophiles?
Grow best at pH 5.5 or below
pH optima of below 1 are very rare
Most cannot grow at pH 7
138
What are alkaliphiles?
Grow best at pH 8 or above
| Found in places like soda lakes and high-carbonate soils
139
What are halophiles?
Require NaCl for growth
140
What does halotolerant mean?
Can tolerate NaCl but grow best in absence of solute
141
What are compatible solutes?
Organic compounds which are highly soluble and don't interfere with cellular metabolism
