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biological sciences year 1 > microbiology > Flashcards

microbiology Flashcards

(74 cards)

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1
Q

What are endospores?

A

highly differentiated cells produced by a certain species of bacteria - they are highly resistant to heat, harsh chemicals and radiation

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2
Q

What is sporulation?

A

the process by which a vegetative cell undergoes a developmental change to form a metabolically inactive and highly resistant endospore

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3
Q

What are fimbriae and pili?

A

filamentous structures composed of protein extending from the surface of a cell. fimbriae enable cells to stick to surfaces and each other

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4
Q

What are the functions of pili?

A

conjugation - genetic exchange between cells and adhesion of pathogens to specific host tissues and subsequent invasion

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5
Q

What is taxis?

A

movement towards something that will aid growth or away from toxins

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6
Q

What is chemotaxis?

A

response to chemicals

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7
Q

What is phototaxis?

A

response to light

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8
Q

What is polar flagellation?

A

when flagella are attached at one or both ends

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9
Q

What is a tuft?

A

a group of flagella attached to one end of the cell

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10
Q

What is peritrichous flagellation?

A

when the flagella is inserted at many locations

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11
Q

What is the myxobacteria glide?

A

vegetative cells excrete slime to move across surface and leave a trail of slime behind

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12
Q

How do you grow microorganisms?

A

need a nutrient solution, requires careful preparation (agar is good)

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13
Q

What are the types of light microscopy?

A

bright-field, phase-contrast, dark-field, fluorescence

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14
Q

How can you image cells in 3D using light microscopy?

A

by using polarised light

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15
Q

How does atomic force microscopy work?

A

measures forces between a probe and atoms on the surface of the specimen - measures deviations from the flat surface

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16
Q

How does confocal scanning laser microscopy work?

A

couples a laser source with a fluorescent microscope - focuses through the specimen layers to make a 3D reconstruction

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17
Q

How does electron microscopy work?

A

uses electrons instead of visible light, whole system operates in a vacuum

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18
Q

What are features of a transmission electron microscope?

A

high magnification and high resolution. can see structures at a molecular level. have to make thin sections of a specimen

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19
Q

What are features of a scanning electron microscope?

A

shows external surfaces of cells. specimen must be coated in a thin film of heavy metal. electrons scatter from metal coating and are collected and processed to form an image

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20
Q

What are the two phyla of archaea?

A

euryacheota and crenarcheota

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21
Q

What are algae?

A

eukaryotes. contain chloroplasts and have cell walls

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22
Q

What is an autotroph?

A

uses CO2 as their carbon source

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23
Q

What is a heterotroph?

A

uses organic compounds as their carbon source

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24
Q

What are chemoorganotrophs?

A

organic chemical feeders - can be aerobic, anaerobic or both

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25
What are chemolithotrophs?
rock chemical feeders - only occurs in prokaryotes
26
What is nitrogen fixation?
some bacterial can covert atmospheric nitrogen gas into a form that can be used by cells
27
What is the equation for nitrogen fixation?
- N2 + 8 H+ + 8 e- -> 2 NH3 + H2
28
What are the two types of nitrogen fixing bacteria?
free living and symbiotic
29
What enzyme catalyses the nitrogen fixation reaction?
nitrogenase
30
What are the two nitrifying bacteria?
nitrosomonas, nitrobacter
31
What do nitrosomonas do?
convert ammonium into nitrites
32
What do nitrobacter do?
convert nitrites into nitrates
33
How can you work out generation time?
g = t/n t= time n= number of generations in time t
34
What is the equation for calculating growth?
N= N02^n N= final cell number N0 = initial cell number 2^n = number of generations during the period of exponential growth
35
What is the lag phase?
time between when culture is inoculated into fresh media and significant growth
36
What is the exponential phase?
when the cell population doubles at regular intervals - the healthiest cell state
37
What is the stationary phase?
when essential nutrient in culture medium runs out and growth rate = 0
38
What is the death phase?
exponential decline of viable cells - rate of cell death faster than rate of growth
39
What are the three ways that you can measure growth?
microscopic counts, viable counts, spectrophotometry
40
How do you do a microscopic count?
count the number of cells present
41
What are the issues with microscopic counting?
without special staining techniques, dead and live cells can't be distinguished. small cells are difficult to see under the microscope. motile cells have to be immobilised
42
What is a viable cell?
able to divide and produce offspring
43
What are the sources of error of a viable cell count?
culture medium, incubation conditions and incubation time have a big effect
44
What is an ecosystem?
A dynamic complex of plant, animal, and microbial communities and their non-living surroundings, which interact as a functional unit
45
What are the living arrangements in a microenvironment?
aerobic organisms live in the outer layers and anaerobic organisms live near the centre
46
What are the oxygen levels in waterlogged soil?
low
47
How far underground does microbial life extend?
at least 3km
48
What organisms are present in freshwater?
both oxygen consuming and oxygen producing
49
What are some oxygenic phototrophs?
algae and cyanobacteria
50
What are the nutrient levels like in coastal and ocean waters?
very low nutrient levels, especially nitrogen, phosphorus and iron
51
What is the photic zone?
where light can penetrate
52
What are hydrothermal vents?
underwater hot volcanic springs - found 1000m to greater than 4000 m deep
53
What are cardinal temperatures?
minimum temp, optimal temp and maximum temp
54
What is the usual pH growth range for microbes?
2-3 pH units
55
What does facultative mean?
under appropriate nutrient conditions, they will grow under either oxic or anoxic conditions
56
What are microaerophiles?
aerobes that can only use oxygen when it's present at levels lower than air
57
What are aerotolerant organisms?
they are anaerobic but they can tolerate oxygen
58
What is an extremophile?
an organism whose growth is dependent on extremes of temperature, salinity, pH, pressure or radiation
59
What is a psychrophile?
optimal growth temperature is 15 degrees celsius or lower. max growth temp is 20 degrees celsius
60
What are psychrotolerant organisms?
they can grow at 0°C, optima is 20-40°C
61
What are adaptations of enzymes that have optimal activity at low temperatures?
primary structure = more polar amino acids, fewer weak bonds. secondary structure = greater alpha helix, less beta pleated sheets - gives protein greater flexibility. high content of unsaturated and shorter-chain fatty acids
62
What are cryoprotectants?
solutes that help prevent formation of ice-crystals in the cell
63
What is a thermophile?
growth temperature optimum is greater than 45°C
64
What is a hyperthermophile?
growth temperature optimum greater than 80°C - found in hot springs - only in prokaryotes
65
How is a thermal gradient formed?
as boiling water leaves hot springs it cools
66
What are the most thermophilic prokaryotes?
archaea
67
What are molecular adaptations to high temperatures?
heat-stable enzymes and proteins, more ionic bonds between basic/acidic amino acids, often higher hydrophobic interiors, increased DNA stability, reverse DNA gyrase (introduced positive supercoils)
68
What is present in hyperthermophile membranes?
do not contain fatty acids. have C40 hydrocarbons bonded to glycerol phosphates by ether link. forms a monolayer
69
What are acidophiles?
grow best at pH 5.5 or below
70
What are alkaliphiles?
grow best at pH 8 or above
71
What must cytoplasmic pH be?
must remain near neutrality - intracellular pH must stay near ph 7 to prevent destruction of macromolecules
72
Why does salt cause problems in the cell?
high salt causes osmotic gradient out of cell and makes the solute potential of the environment more negative
73
What do halophiles require?
NaCl for growth
74
What do halotolerant organisms tolerate?
can tolerate NaCl but grow best in the absence of solute

biological sciences year 1 (16 decks)

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