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biological sciences year 1 > microbiology > Flashcards

microbiology Flashcards

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
Q

What are chemolithotrophs?

A

rock chemical feeders - only occurs in prokaryotes

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26
Q

What is nitrogen fixation?

A

some bacterial can covert atmospheric nitrogen gas into a form that can be used by cells

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27
Q

What is the equation for nitrogen fixation?

A
  • N2 + 8 H+ + 8 e- -> 2 NH3 + H2
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28
Q

What are the two types of nitrogen fixing bacteria?

A

free living and symbiotic

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29
Q

What enzyme catalyses the nitrogen fixation reaction?

A

nitrogenase

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30
Q

What are the two nitrifying bacteria?

A

nitrosomonas, nitrobacter

31
Q

What do nitrosomonas do?

A

convert ammonium into nitrites

32
Q

What do nitrobacter do?

A

convert nitrites into nitrates

33
Q

How can you work out generation time?

A

g = t/n t= time n= number of generations in time t

34
Q

What is the equation for calculating growth?

A

N= N02^n N= final cell number N0 = initial cell number 2^n = number of generations during the period of exponential growth

35
Q

What is the lag phase?

A

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

36
Q

What is the exponential phase?

A

when the cell population doubles at regular intervals - the healthiest cell state

37
Q

What is the stationary phase?

A

when essential nutrient in culture medium runs out and growth rate = 0

38
Q

What is the death phase?

A

exponential decline of viable cells - rate of cell death faster than rate of growth

39
Q

What are the three ways that you can measure growth?

A

microscopic counts, viable counts, spectrophotometry

40
Q

How do you do a microscopic count?

A

count the number of cells present

41
Q

What are the issues with microscopic counting?

A

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
Q

What is a viable cell?

A

able to divide and produce offspring

43
Q

What are the sources of error of a viable cell count?

A

culture medium, incubation conditions and incubation time have a big effect

44
Q

What is an ecosystem?

A

A dynamic complex of plant, animal, and microbial communities and their non-living surroundings, which interact as a functional unit

45
Q

What are the living arrangements in a microenvironment?

A

aerobic organisms live in the outer layers and anaerobic organisms live near the centre

46
Q

What are the oxygen levels in waterlogged soil?

A

low

47
Q

How far underground does microbial life extend?

A

at least 3km

48
Q

What organisms are present in freshwater?

A

both oxygen consuming and oxygen producing

49
Q

What are some oxygenic phototrophs?

A

algae and cyanobacteria

50
Q

What are the nutrient levels like in coastal and ocean waters?

A

very low nutrient levels, especially nitrogen, phosphorus and iron

51
Q

What is the photic zone?

A

where light can penetrate

52
Q

What are hydrothermal vents?

A

underwater hot volcanic springs - found 1000m to greater than 4000 m deep

53
Q

What are cardinal temperatures?

A

minimum temp, optimal temp and maximum temp

54
Q

What is the usual pH growth range for microbes?

A

2-3 pH units

55
Q

What does facultative mean?

A

under appropriate nutrient conditions, they will grow under either oxic or anoxic conditions

56
Q

What are microaerophiles?

A

aerobes that can only use oxygen when it’s present at levels lower than air

57
Q

What are aerotolerant organisms?

A

they are anaerobic but they can tolerate oxygen

58
Q

What is an extremophile?

A

an organism whose growth is dependent on extremes of temperature, salinity, pH, pressure or radiation

59
Q

What is a psychrophile?

A

optimal growth temperature is 15 degrees celsius or lower. max growth temp is 20 degrees celsius

60
Q

What are psychrotolerant organisms?

A

they can grow at 0°C, optima is 20-40°C

61
Q

What are adaptations of enzymes that have optimal activity at low temperatures?

A

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
Q

What are cryoprotectants?

A

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

63
Q

What is a thermophile?

A

growth temperature optimum is greater than 45°C

64
Q

What is a hyperthermophile?

A

growth temperature optimum greater than 80°C - found in hot springs - only in prokaryotes

65
Q

How is a thermal gradient formed?

A

as boiling water leaves hot springs it cools

66
Q

What are the most thermophilic prokaryotes?

A

archaea

67
Q

What are molecular adaptations to high temperatures?

A

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
Q

What is present in hyperthermophile membranes?

A

do not contain fatty acids. have C40 hydrocarbons bonded to glycerol phosphates by ether link. forms a monolayer

69
Q

What are acidophiles?

A

grow best at pH 5.5 or below

70
Q

What are alkaliphiles?

A

grow best at pH 8 or above

71
Q

What must cytoplasmic pH be?

A

must remain near neutrality - intracellular pH must stay near ph 7 to prevent destruction of macromolecules

72
Q

Why does salt cause problems in the cell?

A

high salt causes osmotic gradient out of cell and makes the solute potential of the environment more negative

73
Q

What do halophiles require?

A

NaCl for growth

74
Q

What do halotolerant organisms tolerate?

A

can tolerate NaCl but grow best in the absence of solute

biological sciences year 1 (16 decks)

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