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MICR3310 > 2 - Metabolic & Functional Diversity > Flashcards

2 - Metabolic & Functional Diversity Flashcards

1
Q

Metabolic diversity

A

Range of different metabolic strategies that microbes have to obtain energy

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2
Q

Phylogenetic diversity

A
  • Evolutionary relationships between organisms
  • Genetic and genome diversity of evolutionary lineages
  • Usually based on rRNA gene phylogeny
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3
Q

Important processes underpinned by microbial metabolism

A
  • Primary production (photosynthesis)
  • Carbon capture
  • Decomposition
  • Nitrogen fixation
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4
Q

Microbial metabolism

A

The means by which a microbe obtains the energy and nutrients it needs to live and reproduce (cant make energy from nothing, needs to be captured or conserved

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5
Q

Three critical components of metabolism

A
  • Carbon (auto, hetero)
  • Energy (photo, chemo)
  • Electrons (litho, organo
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6
Q

Autotrophs

A

CO2 principal carbon source

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7
Q

Heterotrophs

A

Reduced, preformed, organic molecules from other organisms

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8
Q

Phototrophs

A

Light energy source

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9
Q

Chemotrophs

A

Oxidation of organic or inorganic compounds

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10
Q

Lithotrophs

A

Reduced inorganic molecules electron source

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11
Q

Organotrophs

A

Organic molecules electron source

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12
Q

Five major nutritional types of microorganisms

A
  1. Photolithoautotroph
  2. Photoorganoheterotroph
  3. Chemolithoautotroph
  4. Chemolithoheterotroph
  5. Chemoorganoheterotroph
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13
Q

Chemical work

A

Synthesis of complex molecules

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14
Q

Transport work

A

Uptake of nutrients, elimination of waste

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15
Q

Mechanical work

A

Motility, movement inside cell (e.g. chromosomes during cell division)

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16
Q

Energy obtained from light, organic or inorganic molecules

A

Must be converted to useful form (most often ATP)

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17
Q

ATP

A
  • High energy molecule
  • Hydrolysis to ADP strongly exergonic
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18
Q

Oxidation-reduction (Redox) reactions

A
  • Electrons move from an electron donor to an electron acceptor
  • Molecules that can donate lots of electrons are energy rich
  • Pairs with more negative potential will spontaneously donate electrons to pairs with more positive potential
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19
Q

Electron donor

A
  • Loses energy
  • Is oxidised
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20
Q

Electron acceptor

A
  • Gains energy (more energy rich)
  • Is reduced
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21
Q

Standard reduction potential

A

Measures the tendency of the donor to lose electrons (one half of reaction)

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22
Q

Free energy

A
  • Energy available to do work
  • Change in free energy expressed as ΔG0’
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23
Q

negative ΔG0’

A

Reaction will process and release free energy (exergonic)

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24
Q

positive ΔG0’

A

Reaction requires energy to proceed (endergonic)

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25
Q

Two ways Chemoorganoheterotrophs capture energy and electrons

A
  • Respiration
  • Fermentation
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26
Q

Chemoorganoheterotrophs

A
  • Chemo: energy from chemicals (not light)
  • Organo: electrons from organic molecules
  • Hetero: carbon from organic molecules
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27
Q

Respiration

A
  • Electrons released by oxidation of energy source (e.g. NAD and FAD) are accepted by carriers
  • These are now reduced (NADH. and FADH2) and donate electrons to the electron transport chain (ETC)
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28
Q

Fermentation

A
  • Does not have electron transport chain
  • Electron acceptor is endogenous
  • Almost all ATP is synthesised by substrate level phosphorylation (SLP)
  • Generates less energy
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29
Q

ETC

A
  • Electrons pass through ETC to the terminal electron acceptor (TEA)
  • Generates proton motive force (PMF)
  • Used to synthesise ATP from ADP + phosphate (via oxidative phosphorylation)
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30
Q

Aerobic respiration

A
  • TEA is oxygen
  • good energy yield
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31
Q

Anaerobic respiration

A
  • TEA varies (but is not O2)
  • Need to process a lot of substrate (NO3) to get good energy
  • e.g. organic molecules fumarate and humic acids
32
Q

Bacteria living in nutrient and oxygen poor environment

A
  • Catabolise molecules and use products as building blocks for essential cell components (uses lots of energy)
  • Use aerobic respiration until O2 is consumed, then switch to anaerobic with alternative TEA
  • If no alternative TEA then fermentation
  • Slow growth
33
Q

Three examples of metabolic diversity

A
  • Phototrophy
  • Chemolithotrophy
  • Fermentations
34
Q

Phototrophy

A
  • Use of light energy
  • Usually also autotrophs (carbon from co2)
35
Q

Photosynthesis

A
  • Conversion of light to chemical energy
  • Requires chlorophylls or bacteriochlorophylls
36
Q

Photoautotrophy reactions that run in parallel

A
  • Light reactions (ATP generation)
  • Dark reactions (co2 reduction)
  • May be oxygenic or anoxygenic
37
Q

Light reactions

A

Energy from light captured and converted to chemical energy

38
Q

Dark reactions

A

Use ATP and reducing power to fix Co2 and synthesise cell components

39
Q

Oxygenic

A
  • O2 produced
  • Cyanobacteria
40
Q

Anoxygenic

A
  • No O2
  • Purple and green bacteria
41
Q

Great oxygenation event (GOE)

A

Point when Cyanobacteria made Earth’s atmosphere oxygenic

42
Q

Main type of chlorophyll of oxygenic phototrophs e.g. cyanobacteria

A
  • Chlorophyll a
  • Absorbs red and blue light and transmits green
43
Q

Bacteriochlorophylls

A
  • Purple and green phototrophic bacteria produce one or more
  • Bacteriochlorophyll a is present in most purple
    bacteria
44
Q

Structure of Chlorophyll and bacteriochlorophyll in oxygenic phototrophs and purple anoxygenic phototrophs

A
  • Both Chl and Bchl are attached to proteins, housed within membranes to form photocomplexes (not free within cell)
  • Contain 50 – 300 Chl /Bchl molecules
  • A few of these photocomplexes are named reaction centres (where ATP generation occurs)
45
Q

Antenna pigments

A
  • Light harvesting Chl/Bchl molecules surround the RC
  • Absorb light and funnel some towards the reaction centre
46
Q

Site of photosynthesis in eukaryotes

A

Within chloroplasts

47
Q

Site of photosynthesis in prokaryotes

A

Chromatophores, lamellae, thylakoids, chlorosomes

48
Q

Chlorophyll absorption

A
  • Only absorb narrow range of light (other light is “wasted”)
  • Additional accessory pigments assist in absorbing wasted light energy
49
Q

Accessory pigments

A
  • Carotenoids and phycobilins
  • Absorb light in blue-green to yellow range
  • light energy then transferred to chlorophyll
  • Enable photosynthesis to occur over a broader range of light wavelengths
  • Also quench toxic oxygen species produced by bright light
50
Q

Carotenoids

A
  • Most widespread accessory pigments
  • Tend to mask colour of Bchls, thus responsible for the colours seen in anoxygenic phototrophs
51
Q

Phycobiliproteins

A
  • Present in cyanobacteria
  • Main light-harvesting systems
  • Assembled into phyobilisomes
52
Q

Chemolithotrophy

A
  • Derive energy from oxidation of inorganic compounds
  • Most are also autotrophs (some are mixotrophs)
  • Can utilise wide range of inorganic compounds as electron donors
53
Q

Mixotrophs

A
  • Require organic compound for carbon
  • Chemolithoheterotrophs
54
Q

Which generates more energy

A

Glucose oxidised completely to Co2 compared to energy derived from inorganic compounds

55
Q

Ecological impacts of oxidation of large quantities of substrate

A

Contributes to global nitrogen, sulphur and iron biogeochemical cycles

56
Q

Why does energy yield from oxidation vary widely

A

Depends on redox pair

57
Q

Autotrophs also need reducing power (NADPH) to fix co2

A
  • Some substrates have more positive reduction
    potentials than NAD(P)+ /NAD(P)H pair (cannot donate electrons directly to NAD(P)*
  • Instead use reverse electron flow to make NADH
58
Q

When does fermentation occur

A
  • Organisms are incapable of respiration (lack ETCs)
  • Organisms unable to respire due to conditions (TEAs for AnO2 respiration are absent)
  • Choose not to respire (synthesis of ETC components repressed)
59
Q

During fermentation

A
  • ATP is synthesised by substrate level phosphorylation
  • NAHD must be oxidised back to NAD+ despite lack of ETC
60
Q

Fermentations

A
  • Many kinds (lactic acid most common)
  • Pathways named after acid or alcohol produced
61
Q

Lactic acid

A
  • Pyruvate reduced to lactate
  • Two groups (homolactic and heterolactic)
62
Q

Homolactic

A

Use Embden–Meyerhof pathway and reduce almost all pyruvate to lactate

63
Q

Heterolactic

A
  • Use pentose phosphate pathway and make lactic acid, CO2, ethanol
64
Q

Three possible explanations for distantly related bacteria sharing same traits

A
  • Gene loss (trait is present in ancestor but is lost by some descendants)
  • Convergent evolution (trait evolves independently
  • Horizontal gene transfer
65
Q

Further divisions of functional diversity

A
  • Physiological diversity
  • Ecological diversity
  • Morphological diversity
66
Q

Physiological diversity

A
  • Relates to functions and activities
  • Usually described in terms of microbial metabolism and cellular biochemistry
67
Q

Ecological diversity

A

relationship between organisms and their environments

68
Q

Morphological diversity

A

Apperance of cells

69
Q

Where did photosynthesis first arise

A

Anoxygenic phototrophs

70
Q

Differences between the six bacterial phyla anoxygenic photosynthesis is present in

A
  • Extensive metabolic diversity present amongst phyla
  • Found in a wide range of habitats
  • Horizontal gene transfer thought to play an important role in their evolution
71
Q

Only bacteria capable of oxygenic photosynthesis

A

Cyanobacteria

72
Q

Examples of Anoxygenic phototrophs

A
  • Purple sulfur bacteria
  • Purple non sulfur bacteria
  • Green sulfur bacteria
  • Green non sulfur bacteria
73
Q

Purple sulfur bacteria

A
  • Found in illuminated, anoxic areas where H2
    S is present (e.g. lakes)
  • Colour comes from carotenoids
  • Use H2S as electron donor (oxidise H2S to S0, deposited as sulphur granules in cell)
74
Q

Purple non sulfur bacteria

A
  • Not always purple (may be red or orange)
  • Very metabolically diverse
  • Usually photoheterotrophs
75
Q

Green sulfur bacteria

A
  • Low metabolic diversity
  • Phylogenetically related
  • Non-motile, strict anaerobes
  • Oxidise H2S to S0 then to SO42-
  • S0 deposited outside the cell
76
Q

S0

A

Elemental sulphur

77
Q

Green non sulfur bacteria

A
  • Many are filamentous, capable of gliding motility
  • Some form thick microbial mats
  • Grow best as photoheterotrophs, but capable of photoautotrophy

MICR3310 (28 decks)

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