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Organisms and environment > Microbiology! > Flashcards

Microbiology! Flashcards

1
Q

What are the three main techniques used for growing bacteria?

A

Slopes
Liquid Culture
Plates

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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.

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3
Q

What did Robert Hooke do?

A

Wrote the first book devoted to microscopic observations

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4
Q

What did Louis Pasteur do?

A

Showed heat could be used to ‘sterilise’

Disproved the idea of spontaneous generation

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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

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6
Q

What are the four key steps in Koch’s postulates?

A
  1. The suspected pathogen must be present in all cases of the disease and absent from healthy animals
  2. The suspected pathogen must be grown in pure culture
  3. Cells from a pure culture of the suspected pathogen must cause disease in a healthy animal
  4. The suspected pathogen must be reisolated and shown to be the same as the original
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7
Q

What are the three domains of life?

A

Prokarya
Archaea
Eukarya

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8
Q

Name some types of microorganisms.

A 
Bacteria
Archaea
Protozoa 
Algae 
Prions
Viruses
Fungi
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9
Q

How many phyla of archaea are there?

A

2

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10
Q

Why is classification of archaea difficult?

A

Majority have not been isolated in the laboratory

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11
Q

Where do protozoa generally live?

A

In soil
Wet sand
Fresh and salt water

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12
Q

Are protozoa prokaryotes or eukaryotes?

A

Eukaryotes

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13
Q

Are protozoa unicellular or multicellular?

A

Unicellular

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14
Q

Describe algae.

A

Eukaryotes
Contain chloroplasts
Have cell walls
Both terrestrial and aquatic

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15
Q

What is an autotroph?

A

Use carbon dioxide as their carbon source
Primary producers
Synthesise new organic matter

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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

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17
Q

What is a symbiotic/ mutualistic relationship?

A

Cooperative relationship with the host

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18
Q

What is a parasitic relationship?

A

Antagonistic relationship with the host

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19
Q

What does saprotrophic mean?

A

The host is dead

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20
Q

What is phototrophy?

A

Obtaining energy from light

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21
Q

What is photosynthesis?

A

Conversion of light to chemical energy

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22
Q

What is the lower limit to cell size?

A

0.15 μm would only just fit in all the essential cellular components

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23
Q

What are the two results you can get from a gram stain test?

A

Gram-positive and gram-negative

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24
Q

What colour do gram-positive bacteria appear?

A

Purple

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25
Q

What colour do gram-negative bacteria appear?

A

Red/ pink

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26
Q

What is an endospore?

A

Highly differentiated cell produced by certain types of bacteria
Resistant to heat, harsh chemicals and radiation
Survival structures

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27
Q

When does sporulation occur and what happens?

A

An essential nutrient is exhausted like carbon or nitrogen
Vegetative cells stop growing
Endospore develops within cell and is released

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28
Q

What happens to an endospore when conditions are good and how long can an endospore remain dormant for?

A

Germinates into vegetative cell when conditions are good

Spore can remain dormant for years

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29
Q

What are three endospore morphologies?

A

Terminal endospore
Subterminal endospore
Central endospore

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30
Q

Can endospores be stained using staining dyes?

A

They are impermeable to most dyes so usually seen as unstained regions within cells

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31
Q

What are the four key layers of an endospore?

A

Exosporium
Spore coat
Cortex
Core

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32
Q

What is the exosporium of an endospore?

A

Thin protein covering

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33
Q

What is the spore coat of an endospore?

A

Layers of spore specific proteins

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34
Q

What is the cortex of an endospore?

A

Loosely cross-linked peptidoglycan

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35
Q

What is the core of an endospore?

A

Core wall, cell membrane, cytoplasm, nucleoid, ribosomes, etc

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36
Q

What are fimbriae and pili?

A

Filamentous structures composed of protein extending from the surface of a cell

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37
Q

What is the purpose of fimbriae? What is the negative of this?

A

Enable cells to stick to surfaces and each other

Can assist the disease process

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38
Q

How do pili differ from fimbriae?

A

Typically longer, and only one or two present

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39
Q

What are the two major functions of pili?

A
  1. Conjugation: genetic exchange between cells
  2. Adhesion of pathogens to specific host tissues for subsequent invasion

May also help with mobility

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40
Q

What are the two major types of bacterial cell movement?

A

Swimming

Gliding

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41
Q

Why do microbial cells need to move under their own power?

A

Enable the cell to reach different parts of their environment

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42
Q

What do flagellum do?

A

The flagellum rotate to push or pull a cell through a liquid

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43
Q

What are three different types of attachments of flagella?

A

Polar flagellation
A tuft
Peritrichous flagellation

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44
Q

What is polar flagellation?

A

Flagella are attached to one or both ends

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45
Q

What is a tuft of flagella?

A

A group of flagella attached to one end of the cell

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46
Q

What is peritrichous flagellation?

A

Flagella inserted at many locations

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47
Q

What is the structure of flagella?

A

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

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48
Q

How does the flagellum get energy for rotation?

A

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

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49
Q

Is gliding slower or faster than swimming with flagella?

A

Much slower

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50
Q

What is taxis?

A

Movement towards something that will aid growth or away from toxins

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51
Q

What is chemotaxis?

A

Response to chemicals

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52
Q

What is phototaxis?

A

Response to light

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53
Q

Describe myxobacteria.

A

Multicellular structures
Life cycles indicate intercellular communication
Form fruiting bodies- often striking colours and morphology
Glide- slime trails

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54
Q

How do bacterial cells glide?

A

With slimes and pili

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55
Q

What is chemotrophy?

A

Obtaining energy from chemicals

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56
Q

What do chemolithotrophs do?

A

Oxidation of inorganic compounds releases energy, stored at ATP

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57
Q

Are chemolithotrophs eukaryotes or prokaryotes?

A

Prokaryotes

58
Q

Why is being a chemolithotroph a good metabolic strategy?

A

Competition is not an issue
Many of the inorganic compounds they use are waste products of chemoorganotrophs
Can live in association with chemooganotrophs

59
Q

What do chemoorganotrophs do?

A

Oxidation of organic compounds to release energy

Can be aerobic or anaerobic or both

60
Q

What is nitrogen fixation?

A

Convert atmospheric nitrogen gas into a form that can be used by cells
No known eukaryotes can fix nitrogen

61
Q

What are the two types of nitrogen fixing bacteria?

A

Free-living

Symbiotic

62
Q

Define free-living.

A

Require no host, they live free

63
Q

Define symbiotic nitrogen fixing bacteria.

A

Can only exist in association with certain plants

Live in root nodules

64
Q

What is nitrification?

A

Oxidation of inorganic nitrogen compounds performed by nitrifying bacteria

65
Q

Where are nitrifying bacteria mostly found?

A

In soils and water

66
Q

Why is nitrification important for industry?

A

Plant productivity

Sewage and wastewater treatment: Removing toxic amines and ammonia

67
Q

What are the key cycles?

A

The Carbon Cycle
The Nitrogen Cycle
The Sulphur Cycle

68
Q

What is humus?

A

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
Q

Define growth for multicellular organisms.

A

Growth involves the whole organism getting bigger

70
Q

Define growth for single celled organisms.

A

Growth is defined as an increase number of cells in a population

71
Q

What is binary fission and which organisms replicate via this method?

A

One cells divides into two
Prokaryotes and some eukaryotes
All bacteria

72
Q

What is generation time?

A

Time for one cell to split into two in binary fission

73
Q

What is the generation time of E. coli in lab culture?

A

About 20 mins

74
Q

How does generation time vary between lab cultures and cells in nature?

A

Cells grow much slower in nature where conditions are not optimised
Generation times of hours or days are more common

75
Q

What does each daughter cell receive in binary fission?

A 
A chromosome
Ribosomes
Macromolecular complexes like proteins
Monomers
Inorganic ions
76
Q

Where does genetic variation come from in bacteria?

A

High mutation rate
Each new generation carries DNA with mutations compared to its parent and therefore has the power to evolve
Conjugation

77
Q

What are the phases of the growth cycle?

A

Lag
Exponential
Stationary
Death

78
Q

What is the lag phase?

A

Time between when culture is inoculated into fresh media and significant growth

79
Q

What does the length of the lag phase depend on?

A

History of the inoculum
Nature of the medium
Growth conditions

80
Q

What is the exponential phase?

A

Cell population doubles at regular intervals

81
Q

What does the length of the exponential phase depend on?

A

Availability of environmental conditions: temperature, nutrients, etc
Genetic characteristic of the organisms

82
Q

What is the healthiest cell state in the cell cycle?

A

Exponential phase

83
Q

What happens in the stationary phase?

A

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
Q

What happens in the death phase?

A

Exponential decline of viable cells

Rate of cell death typically faster than rate of growth

85
Q

Describe batch culture.

A

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
Q

Describe a continuous culture.

A

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
Q

What can be controlled in a chemostat?

A

Growth rate

Cell density

88
Q

What is the dilution rate?

A

Rate fresh medium is added and spent medium is removed

89
Q

What is the issue caused by the dilution rate of a continuous culture being too small?

A

Cells die from starvation

90
Q

What is the issue caused by the dilution rate of a continuous culture being too high?

A

Cells can’t grow fast enough and are washed out of the vessel

91
Q

What is a microscopic count?

A

Count the number of cells present

Samples dried onto slides or liquid samples

92
Q

What are issues with microscopic counting?

A

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
Q

What is a viable count?

A

A plate count

Main assumption is each viable cell will divide to make one colony

94
Q

What is a viable cell?

A

Able to divide and produce offspring

95
Q

What are some issues of a viable count?

A

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
Q

What is a microenvironment?

A

Microorganisms are very small so only directly experience a tiny local environment
Numerous microenvironments can exist within a given habitat

97
Q

What can we use to measure oxygen concentration in a soil particle?

A

Microelectrodes

98
Q

How do organisms living in a soil particle differ from the inside to the outer layers?

A

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
Q

What do mineral soils form from?

A

Weathering rock and inorganic materials

100
Q

What do organic soils form from?

A

Sedimentation in bogs and marshes

101
Q

Are most soils mineral or organic?

A

Most soils are a mixture of the two

Mineral based soils predominate

102
Q

What is groundwater?

A

Water in soils and rocks deep underground

103
Q

Describe oxygenic phototrophs.

A

Include algae and cyanobacteria
Primary producers: energy comes from light
Often floating
Attached to bottom or sides of lake/ stream (benthic)

104
Q

Describe the characteristics of coastal and ocean waters.

A

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
Q

Describe the characteristics of freshwater.

A

Highly variable in resources and conditions
Both oxygen consuming and oxygen producing organisms present
The balance controls the cycle of nutrients

106
Q

How are microbes in the ocean different to in other habitats?

A

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
Q

Why are oceanic microbes important?

A

Oxygenic photosynthesis in the oceans is a major factor in controlling the Earth’s carbon balance because the oceans are so large

108
Q

What is the photic zone?

A

Where light can penetrate to in a body of water

109
Q

What is the deep sea and how much of the ocean water is deep sea?

A

Deep sea is 1000m below sea level

>75% ocean water is deep-sea water

110
Q

Describe the characteristics of the deep sea.

A

Low temperature
High pressure
Low nutrients

111
Q

What are hydrothermal vents?

A

Underwater hot volcanic springs

Found 1000 m to greater than 4000 m deep

112
Q

What are the abiotic growth factors?

A 
Nutrient availability
Temperature
pH
Moisture
Oxygen
Pressure
Light
113
Q

What is the minimum temperature for a species?

A

Growth isn’t possible below this temperature

114
Q

What is the optimum temperature for a species?

A

Growth is most rapid at this temperature

115
Q

What is the maximum temperature for a species?

A

Growth isn’t possible above this temperature

116
Q

What pH range do most natural environments lie within?

A

4-9

117
Q

What growth range of pH units do most microbes show?

A

2-3

118
Q

What must intracellular pH remain relatively constant at?

A

Neutral, aside from extremophiles

119
Q

What are two considerations in water availability?

A
  1. Absolute water availability: how moist/dry it is

2. Osmotic potential: concentration of solutes such as salts/ sugars

120
Q

What is water activity?

A

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
Q

What does aerobic mean?

A

Grow at full oxygen tensions

Respire oxygen

122
Q

Define anaerobic.

A

Cannot respire oxygen
Obligate anaerobes are inhibited or even killed by oxygen
There are no anaerobic algae

123
Q

Define facultative.

A

Under appropriate nutrient conditions will grow under either oxic or anoxic conditions

124
Q

Define microaerophiles.

A

Aerobes than can only use oxygen when it is present at levels lower than air

125
Q

Define aerotolerant.

A

Anaerobic but can tolerant oxygen

However, they do not use oxygen in their metabolism

126
Q

What is an extremophile?

A

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
Q

Describe a psychrophile.

A

Optimal growth temperature 15 degrees celsius or lower
Max growth temp 20 degrees celsius
Killed by warming, found in constantly cold environments

128
Q

What does psychrotolerant mean?

A

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
Q

What is snow algae?

A

On the surface of permanent snow fields and glaciers
Pink discolouration
Red-pigmented spores
Germinate to form mobile green algal cells

130
Q

What are some molecular adaptations to the cold?

A

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
Q

What are “cold-shock” proteins?

A

Maintain other proteins activity and bind specific mRNAs to facilitate their translation at cold temps
Often in psychrophiles

132
Q

What are cryoprotectants?

A

Solutes that help prevent the formation of ice-crystals in the cell

133
Q

What is a thermophile?

A

Growth temp optimum greater than 45 degrees
Less extreme than hyperthermophiles
Found in range of habitats like the edges of hot springs

134
Q

What is a hyperthermophile?

A

Growth temp optimum greater than 80 degrees
Found in hot springs
Only prokaryotes
Growth rates often quite high

135
Q

Can prokaryotes or eukaryotes grow at higher temperatures?

A

Prokaryotes

136
Q

What are some molecular adaptations to high temperatures?

A

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
Q

What are acidophiles?

A

Grow best at pH 5.5 or below
pH optima of below 1 are very rare
Most cannot grow at pH 7

138
Q

What are alkaliphiles?

A

Grow best at pH 8 or above

Found in places like soda lakes and high-carbonate soils

139
Q

What are halophiles?

A

Require NaCl for growth

140
Q

What does halotolerant mean?

A

Can tolerate NaCl but grow best in absence of solute

141
Q

What are compatible solutes?

A

Organic compounds which are highly soluble and don’t interfere with cellular metabolism

Organisms and environment (6 decks)

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