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Biosci 3313: Microbiology > Exam 3 > Flashcards

Exam 3 Flashcards

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1
Q

Define science

A

Experimental, hypothesis-driven investigation of phenomena to elucidate (1) patterns in nature and (2) the processes governing the formation, maintenance, and changing of those patterns

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2
Q

What are the three parts of a scientific statement?

A

Cause -> Verb -> Effect

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3
Q

Where do Psychrophiles thrive?

A

Temperatures below 25*C

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4
Q

Where do Mesophiles thrive?

A

Temperatures between 20 and 35*C

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5
Q

Where do Thermophilies thrive?

A

Temperatures between 40 and 80*C (These were the bacteria present on early earth)

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6
Q

Where do Hyperthermophiles thrive?

A

Temperatures above 80*C

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7
Q

How can certain bacteria survive extreme heat?

A

Saturated fat membrane lipids, enzymes modified to be more stable at higher temperatures, and more GC content in DNA

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8
Q

Define Halotolerant organisms

A

do not mind salt

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9
Q

Define Halophilic organisms

A

thrive with 3% salt

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10
Q

Define Extreme Halophiles

A

thrive with 15+% (above saturation level of water)

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11
Q

Describe the ability of halophiles to counter salt

A

Salt pulls water out of the cell, halophiles counter this with organic solutes
Gram positive organisms tend to be more halotolerant

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12
Q

Define obligate aerobes

A

Must have O2 to use as terminal electron carrier

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13
Q

Define facultative aerobes

A

Can use O2 or anaerobic pathways

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14
Q

Define microaerophiles

A

Require O2 levels between 2-10%

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15
Q

Define obligate anaerobes

A

Killed by O2

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16
Q

Define tolerant anaerobes

A

Can survive O2, do not use it for energy

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17
Q

What tool can we use to determine the optimum oxygen levels for a particular microorganism? What would those look like for each organism?

A

Tubes with resazurin (pink=O2, clear=no) And thioglycate agar can be used to determine the optimum oxygen levels for a particular microorganism

Obligate Aerobe grow on top, Facultative Aerobe clusters near the top, Microaerophile have a high band, Obligate Anaerobes grow on the bottom, and Tolerant Aerobes grow evenly throughout

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18
Q

What are the components of Chlorophyll?

A

Porphyrin (rings), with magnesium and lipid side chains

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19
Q

What are the subtypes of Chlorophyll?

A

Chlorophyll a - plants, algae, cyanobacteria - red and blue
Chlorophyll b - plants, algae, cyanobacteria - red and blue
Bacteriochlorophyll a - infrared

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20
Q

What is the benefit of different absorption spectra among chlorophyll sub types?

A

Allows for more flexibility of light used, less competition.

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21
Q

What is the photosynthetic reaction center?

A

Complex of proteins and pigments that together execute photosynthesis.

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22
Q

Define Photophosphorylation

A

Conversion of light energy to chemical energy

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23
Q

What is a photoautotroph?

A

An autotroph that is also a phototroph. Most phototrophs are autotrophs.

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24
Q

How do phototrophs convert light energy into chemical energy?

A

Via proton motive force- use an electron transport chain and chemiosmosis

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25
Q

What are the two major classes of photophosphorylation?

A

Anoxygenic (cyclic photophospohrylation) and Oxygenic

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26
Q

What is the electron source in anoxygenic photosynthesis?

A

H2S and organic compounds

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27
Q

What is the electron source used for in anoxygenic photosynthesis?

A

to transfer between reaction center and electron transport chain (light to P870)

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28
Q

How is P870 as an electron donor?

A

Can be either a strong or a poor donor, depending on if it is excited by light energy

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29
Q

What is anoxygenic photosynthesis also known as? Why?

A

Cyclic photophosphorylation. The electrons travel in a cycle and the chlorophyll both receives and donates an electron.

30
Q

Describe the process of Cylic photophosphorylation

A

Light excites the chlorophyll (P870, etc) → other chlorophylls → quinones → Q pool → cytochromes → back to chlorophyll

31
Q

What is the goal of Cylic photophosphorylation?

A

Generates PMF (proton motor force) and recycles electrons

32
Q

What generates the PMF in Cyclic photophosphorylation?

A

Electron transfer from quinones to cytochromes

33
Q

What can Quinones carry? What can cytochromes carry?

A

Quinones carry both H+/e-, cytochromes carry only e-

34
Q

What type of organisms employ anoxygenic photosynthesis?

A

Purple non-sulfur, purple sulfur, and green sulfur bacteria

35
Q

What is the electron source in oxygenic photosynthesis?

A

H2O

36
Q

What types of organisms employ Oxygenic photosynthesis?

A

Plants, algae and cyanobacteria

37
Q

What are the mechanisms behind oxygenic photosynthesis?

A

2 distinct, interconnected photosystems (I and II) -> non-cyclic

38
Q

Differentiate between photosystem I and II

A

Photosystem II (P680) generates ATP, Photosystem I (P700) generates NADPH

39
Q

Describe the “Z” scheme of electron flow employed by oxygenic photosynthesis

A

Starts at Photosystem II (P680)
Electrons go from H2O → P680 → Pheophytin → Quinone → Cytochrome bf → Plastocyanin
Plastocyanin transfers electrons to Photosystem I (P700).
P700 → Carrier → reduces Ferredoxin → Flavoprotein→ reduce NAD(P)+
Ferredoxin can also donate back to the Cytochrome bf to create the cyclic electron flow

40
Q

What type of photosynthesis do cyanobacteria employ?

A

Oxygenic

41
Q

What type of pigments does Cyanobacteria have?

A

Chlorophyll a and phycobilins

42
Q

Describe the types of Phycobilins. How are they arranged and what is this arrangement called?

A

Phycobilins = phycoerythrin (blue) and phycocyanin (red)

Arranged in antenna like complexes - phycobilisomes to help gather light

Composition influenced by light

43
Q

Cyanobacteria are responsible for what percent of CO2 fixation in aquatic environments?

A

50%

44
Q

Describe the environment that cyanobacteria normally dwell in

A

Cyanobacteria are widely dispersed (fresh water, marine water, hot springs, deserts). They are found on and in rocks (they have a role in erosion protection)

45
Q

What is the role of nitrogen fixation for cyanobacteria?

A

Many cyanobacteria employ nitrogen fixation, often in symbiosis with plants.

46
Q

Define Scytonemin

A

Pigment that protects Cyanobacteria from UV damage

47
Q

Define Cyanophycin

A

Only known nitrogen storage molecule, a polymer of aspartic acid and arginine

48
Q

What are the negative qualities of Cyanobacteria?

A

Nuisance blooms in freshwater, produce potentially lethal toxins, odor and taste problems in drinking water.

49
Q

Describe the use of temporal separation by certain species of Cyanobacteria

A

can fix N2 in presence of O2 using temporal separation, fix N2 at night and photosynthesize at day

oxygen damages the N2 generating mechanisms

50
Q

What is a baeocyte?

A

a reproductive cell that grows to a large size while replicating its DNA over and over until it quickly splits into many cells

51
Q

What does it mean to divide in a single plane?

A

Filaments are chains of cells that form when the plane division is fixed resulting in a 1D colony (grow in strings, may also mean only one direction)

52
Q

What is a heterocyst?

A

larger thick walled cells found in the filaments of certain cyanobacteria that fix nitrogen alongside vegetative cells that undergo photosynthesis

53
Q

What are subcultures? What can they allow?

A

Subcultures are where samples are taken from a saturated culture and placed into a new environment with more resources, can allow two populations of bacteria to diverge

54
Q

Define Pan Genome

A

All genes present in all populations of a species

55
Q

Individuals can survive loss of function if:

A

if others in the population still provide that function

56
Q

What are the four ways Diversity can arise?

A

Random mutations,

Selective Pressures/Natural Selection,

Genetic Drift (Different populations arising from sampling variation),

Horizontal gene Transfer (Transformation, conjugation, or transduction)

57
Q

How do mutations arise?

A

Spontaneously, not as a physiological response

58
Q

How do you determine the minimum number of generations between two species and their most recent common ancestor?

A 
Fewer differences → more recent common ancestor 
# of differences / 2 = min # of generations (one mutation per, no back mutations)
59
Q

Describe Chronometers/Molecular Clocks

A

A technique that uses the mutation rate of nucleic acids or proteins to figure out the time since divergence between the two organisms

60
Q

What do all organisms have that serve as scaffolding for their ribosomes? What does this mean?

A

rRNA.

Since it is serving the same function, it will have many conserved regions.

Lets us know about the 3 domains of life

61
Q

How are Phylogenetic trees created?

A

Align Sequences → Produce a Distance Matrix (differences from each organism to the others) → Create A Tree

62
Q

Enzymes that help bacteria survive oxygen

A

superoxide dismutase, catalase, and peroxidase

63
Q

Winogradsky column

A

Top has high levels of oxygen and low levels of sulfur, bottom is opp
Cyanobacteria → Purple Nonsulfur Bacteria → Purple Sulfur Bacteria → Green Sulfur Bacteria → (Sulfate producers)

64
Q

What are akinetes?

A

Enveloped, thick-walled dormant cell that is resistant to cold and desiccation

resting spores

65
Q

What are hormogonia?

A

a portion of filament in some cyanobacteria that becomes detached and reproduces by cell division

fragmented filaments

66
Q

Describe the flucuation experiment by delbruck and luria that demostrated that mutations occur spontaneously, not as a result of selective pressure

A

Resistance is random and passed to offspring, not a physiological response to a bactericide
One large flask that is plated 20 times will produce similar numbers of resistant bacteria
One large flask that is subcultured into 20 different cultures will produce a varied number of resistant bacteria per plate

67
Q

Why is 16S rRNA used to study evolution?

A

In every living thing

Made of conserved sequences (both broad and specific) and variable sequences

Conserved sequences are used to design primers to amplify DNA so it can be sequenced and compared with others to create phylogenetic trees

The variable sequences = areas where changes can accumulate

Very large sequence, lot of room for changes t

68
Q

Describe bacterial growth with a single sugar

A

Lag Phase → Log Phase → Stationary (→ Death)

69
Q

Describe diauxic bacterial growth

A

Lag → Log → Stationary → Slower Log Phase → Stationary (→ Death)

First stationary phase -> 𝜷-galactosidase is produced, concentration
increases before leveling off

Concentration of first sugar remains steady until first log phase

Concentration of the second sugar remains steady until the second log phase

70
Q

How can the concentration of sugar enzymes be monitored?

A

using substrates that produce a color when cleaved by 𝜷-galactosidase

71
Q

How can you stop the production of an enzyme?

A

Turn of transcription, turn off translation, destroy with proteases, do not activate with phosphorylation or methylation

Biosci 3313: Microbiology (4 decks)

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