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BS1040: Microbiology and Cell Biology > MC5-6: Bacterial metabolism and phototrophy > Flashcards

MC5-6: Bacterial metabolism and phototrophy Flashcards

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1
Q

When did bacteria evolve?

A

Approx. 3.5 billion years ago

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2
Q

How many species of animals, plants, and bacteria are there on Earth?

A

Animals: 10–30 x106

Plants: (estimated) 300,000

Bacteria: (estimated) 107 – 109

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3
Q

How many cells are there on Earth at any one time?

A

4–6 x1030 cells

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4
Q

Where are the majority of bacteria and archaea found?

A

Open ocean: 1.2 x1029

Soil: 2.6 x1029

Oceanic sediment: 3.5 x1030

Terrestrial sediment: 0.25–2.5 x1030

Human guts: approx. 3.9 x1023

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5
Q

Define ‘metabolism’

A

The set of chemical reactions that occur in living organisms in order to mainain life. Metabolic processes allow organisms to grow, reproduce, maintain structures, and respond to their environments

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6
Q

Define ‘catabolism’

A

Breaking down organic matter, e.g. to harvest energy in cellular respiration

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7
Q

Define ‘anabolism’

A

The use of energy to contruct components of cells such as proteins and nucleic acids

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8
Q

What are the three basic requirements for life?

A
  1. Energy source
  2. Carbon source
  3. Electron source
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9
Q

What are the two different possibilities for obtaining energy, and what are the processes that lead to energy obtention?

A
  • Phototrophy – ‘eating’ light energy
    • Photosynthesis – converting CO2 to sugars using sunlight energy
  • Chemotrophy – ‘eating’ chemical bond energy
    • Respiration – transforming energy from nutrients into chemical energy with O2 usually as the terminal electron acceptor
    • Fermentation – process of energy production in cell under anaerobic conditions
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10
Q

What is the so-called ‘energy currency’ of bacteria, and what are the two methods by which this is generated?

A

ATP

Substrate-level phosphorylation and oxidative phosphorylation

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11
Q

What are the carbon sources of:

  1. autotrophs
  2. hterotrophs?
A
  1. Autotrophs = CO2
  2. Heterotrophs = organic compounds
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12
Q

Where do:

  1. photoautotrophs
  2. photoheterotrophs
  3. chemoheterotrophs
  4. chemoautotrophs

get their energy and carbon from?

A
  1. Photoautotroph
    Energy = light
    Carbon = CO2
  2. Photoheterotroph
    Energy = light
    Carbon = organic compounds
  3. Chemoheterotroph
    Usually, a single organic compound acts as a source for both energy and carbon
  4. Chemoautotroph
    Energy = oxidation of inorganic chemical compounds
    Carbon = CO2
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13
Q

What are the four nutritional categories of life?

A
  • Photoautotroph
  • Photoheterotroph
  • Chemoautotroph
  • Chemoheterotroph
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14
Q

Why can O2 be very harmful to organisms without protective mechanisms?

A

It is a harsh oxidising agent

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15
Q

What is the name for organisms that can grow in oxygen?

A

Aerobes

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16
Q

How do aerobes utilise oxygen?

A

They use aerobic respiration as their principle energy generation by using O2 as their terminal electron acceptor

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17
Q

Why can anaerobes not live in oxygenated environments?

A

They never developed protective mechanisms against oxygen

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18
Q

Give two examples of environments in which anaerobes live.

A
  • Animal intestinal tract
  • Lake/ocean sediments
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19
Q

What is different about anoxygenic photosynthesis?

A
  • Carried out in oxygen-free environments
  • Electron donor is water
  • No oxygen is produced
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20
Q

What are the types of aerobic and anaerobic metabolism?

A

Aerobic

  • Aerobic respiration
  • Oxygenic photosynthesis
  • Anoxygenic photosynthesis

Anaerobic

  • Fermentation
  • Anaerobic respiration
  • Anoxygenic photosynthesis
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21
Q

How is ATP generated in bacteria?

A

Phototrophy

  • Pigments absorb energy from the sun
  • An electron with a higher energy level is then released from within the pigment
  • This electron is passed through an electron transport chain, with the generation of energy by formation of ATP
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22
Q

What is the carbon source of:

  1. autotrophs
  2. heterotrophs
  3. mixotrophs?
A
  1. Autotrophs: CO2
  2. Heterotrophs: organic compounds
  3. Mixotrophs: both
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23
Q

What are the two types of phototrophy and how do they differ?

A
  • Anyoxygenic
    • Used bacteriochlorophyll
    • Has 1 reaction centre
  • Oxygenic
    • Uses chlorophyll
    • Has 2 reaction centres
24
Q

What are the five major groups of prokaryotes that use anoxygenic photosynthesis, and which group used oxygenic photosynthesis?

A

Anoxygenic

  • Purple sulphur bacteriochlorophyll b
  • Purple non-sulphur bChl a b
  • Green non-sulphur bChl a b
  • Green sulphur bChl c d e f
  • Heliobacteria bChl g

Oxygenic

  • Cyanobacteria chla
25
Q

What do purple sulphur bacteria use as an electron donor? Give examples of the bacteria.

A
  • H2S
  • Thiopedia roseopersicinia
  • Ameobacter purpureus
26
Q

What do purple non-sulphur bacteria use as an electron donor? Give examples of typical genera.

A
  • Hydrogen
  • Rhodospirillum
  • Rhodopseudomonas
  • Rhodobacter
27
Q

What do green sulphur bacteria use as electron donors? Give examples of species.

A
  • H2S / S / S2O32– (which invariably becomes H2SO4)
  • Chlorobium species
28
Q

What do green non-sulphur bacteria use as electron donors? Give an example of a species.

A
  • Hydrogen
  • Chloroflexus
29
Q

What do heliobacter use as an electron donor?

A

H2S

30
Q

What are the only oxygenic phototrophic prokaryotes?

A

Cyanobacteria

31
Q

What do cyanobacteria use as an electron donor? Name the two main genera

A
  • Water
  • Synechococcus
  • Prochlorococcus
32
Q

What are the seven reasons for studying microbial metabolism?

A
  1. Medical microbiology
  2. Microbiome
  3. Diagnostic microbiology
  4. Pharmaceutical microbiology
  5. Biotechnology
  6. Many foods/drugs of plant origin owe their taste/smell/active constituents to microbial metabolism
  7. Environmental microbiology
33
Q

How is energy accessed by chemotrophs?

A

By harnessing and linking oxidation/reduction pairs

34
Q

What does OILRIG mean?

A
  • *O**xidation
  • *I**s
  • *L**oss (of electrons)
  • *R**eduction
  • *I**s
  • *G**ain (of electrons)
35
Q

On which side of a redox pair is the oxidised form always written?

A

Left

36
Q

What is the redox potential and how is it measured?

A

Redox potential = E’0 = the capacity of a pair to donate or accept electrons

Measured electrically by reference to a standard

37
Q

Finish the sentence:

Half-reactions with positive redox tend to ______ electrons; half-reactions with negative redox tend to ______ electrons.

A

Half-reactions with positive redox tend to donate electrons; half-reactions with negative redox tend to accept electrons.

38
Q

What are the two mechanisms chemoheterotrophs have for energy conservation?

What drives the synthesis of ATP in both?

A

Respiration and fermentation

Driven by energy released in redox reactions

39
Q

Describe the oxidase test

A
  • Filter paper impregnanted with redox dye (TMPD) which artificially donates an electron to the cytochrome
  • The cytochrome system is usually only present in aerobic organisms that are capable of using electron as the terminal electron acceptor
  • Turns purple if the dye is oxidised by oxygen released from metabolic reaction
40
Q

Where do Deinococcus species of bacteria grow?

A

On sugars, amino acids, organic acids, and mixtures of these

41
Q

What is the best studied of the Deinococcus species?

A

D. radiodurans

42
Q

Give two examples of Spirochetes and the diseases they cause.

A
  1. Treponema – causes syphilis
  2. Borrelia – causes Lyme disease
43
Q

What is the relevance of Spricohetes having a helical structure?

A

It allows them to move in a corkscrew motion through viscous media such as mucus

44
Q

What do Planctomyces lack in their cell walls?

A

Peptidoglycan

45
Q

What type of prokaryote produce methane?

A

Methanogenic archaea in anoxic environments

46
Q

What are methanotrophs and methylotrophs?

A
  • Methanotrophs produce methane
  • Methylotrophs grow on one-carbon compounds including methane
47
Q

What are diazotrophs? Give an example.

A

Bacteria that reduce nitrogen (N2)

e.g. Azotobacter

48
Q

Are Azotobacter Gram positive or Gram negative?

A

Gram negative

49
Q

How do Azotobacter contribute to biogeochemical cycling?

A

They grow on a range of carbohydrates, alcohols, and organic acids and fix N2 non-symbiotically

50
Q

What are Rhizobia?

A

N2-fixing symbiont of legumes

51
Q

How are chemoautotrophs specialist?

A

They can find unique niche zones where chemoheterotrophs cannot live

52
Q

What are the three sources of inorganic electron donors?

A
  1. Geological
    • e.g. volcanic activity producing H2S
  2. Biological
    • Producing H2S, H2, NH3
  3. Anthropogenic (human influence)
    • e.g. agriculture, mining, burning fossil fuels, input of industrial wastes
53
Q

Give examples of the chemoautotrophs that are at the heart of most nutrient cycles

A

Aquifex, nitrosifyers such as Nitrosococcus, nitrifyers such as Nitrobacter, Thiobacillus, Thiomicrospira, Thiothrix

54
Q

Describe the metabolism of nitrosifiers

A

They oxidise ammonia to to nitrites

55
Q

Describe the metabolism of nitrifyers

A

They oxidise nitrites to nitrates

56
Q

Describe the metabolism of sulphur-oxidising bacteria

A

They oxidise sulphur, using oxygen as a terminal electron acceptor

57
Q

Describe the metabolism of iron-oxidisers

A

They oxidise iron:

  • Ferric iron to insoluble ferric hydroxide which precipitates in water
  • Ferrous iron to ferric state at neutral pH

BS1040: Microbiology and Cell Biology (25 decks)

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