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Diversity of Plants and Microorganisms > Bacteria Groups > Flashcards

Bacteria Groups Flashcards

1
Q

Examined groups of Bacteria

A
  1. Firmicutes and Actinobacteria
    - Firmi0cutes - ‘strong-skin’
    - Actinobacteria - ‘rayed bacteria’
  2. Proteobacteria - ‘variable bacteria’
  3. Cyanobacteria - ‘blue-green bacteria’
  4. Spirochaetes - ‘Spiraled Hairs’
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2
Q

Examined groups of Bacteria

A
  • Firmicutes
  • Actinobacteria
  • Proteobacteria
  • Cyanobacteria (& briefly, other photosynthesizers)
  • Spirochetes
    Some others
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3
Q

Firmicutes (Bacillota)

A

Classically, Gram-positive cell envelope
- inc. main ‘models’ fro the Gram-positive envelope

  • Most are organotrophs
  • Range from obligate aerobes to obligate anaerobes
  • Many specialist fermenters
  • Most common in soil, sediments
  • Many live on animals and/or are pathogenic
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4
Q

Examples of Firmicutes

A
  • Lactic Acid Bacteria
  • Endospore formers
  • e.g. Bacillus, Clostridium
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5
Q

Lactic acid bacteria

A
  • Aerotolerant anaerobes (can live in oxygen, can’t use it)
  • No respiration
  • Ferment simple sugars to lactic acid (lactate)
  • e.g. lactic fermentation**
  • ‘Lactic’ (Homolactic), Glucose
    -> 2 Lactate + 2H
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6
Q

Lactic acid bacteria - habitats

A

Mostly in carbohydrate-rich habitats, e.g.
- Decaying plant material
- Mouth, gastrointestinal tract; vagina
- Pickling and dairy industry - acid production inhibits other microbes (& adds flavour)

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7
Q

Endospore-formers

A

Example: Bacillus
- Mostly found in soil/sediment
Endospores a dormancy stage
- Very resistant to heat, desiccation, UV, etc.
- Some viable for decades

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8
Q

Ensospore composition

A
  • A thick Cortex of modified peptidoglycan (and protein coat)
    … surrounds the Core, Contains nucleoid (i.e. DNA) & inactive cytoplasm; Very low water content
  • DNA bound to protective Small Acid-Soluble Proteins
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9
Q

Endospore formation (‘sporulation’)

A

Go to slides

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10
Q

Pathogenic endospore-formers

A
  1. Anthrax: Bacillus anthracis
  2. Some severe food poisoning:
    - Clostridium perfringens
    - Botulism (Clostridium botulinum)
  3. Infections of puncture wounds
    - Gangrene (Clostridium perfringens)
    - Tatanus (Clostridium tetani)
  4. Diarrheal disease
    - Clastridioides difficile (C. diff)
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11
Q

Actinobacteria (Actinocycetota)

A
  • Gram-positive cell architecture
  • Organotrophs; Generally aerobic
  • Abundant in soil
  • Most are Filaments (e.g. Streptomyces)
  • Some unicellular
  • e.g. Mycobacterium (tuberculosis; leprosy)
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12
Q

Filamentous Actinobacteria

A
  • Filaments often indefinite length (i.e. septae rare)
  • Can branch & extend as mycelium
  • (many copies of genome)
  • Usually produce thick-walled spores
  • (called ‘exospores’ or ‘arthrospores’)
  • Resist desiccation
  • Different from endospores or Firmicutes
  • e.g. form by multiple fission
  • Reproductive, & function is dispersal
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13
Q

Filamentous Actinobacterium (e.g. Streptomyces)

A
  • Nutrient acquisition via grow of substate mycelium
  • Then aerial mycelium grow and produce arthrospores
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14
Q

Streptomyces

A

~500 different species describes (3% of all prokaryotes)
- Grow on (break down) many difficult-to-degrade polysaccharides (e.g. chitin); also lignin
- Thus important in decomposition in soil
- Antibiotic production
- Origin of ~50% of therapeutic antibiotics

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15
Q

Mycobacterium

A

Primarily soil bacteria; but some serious pathogens:
e.g. Mycobacterium tuberculosis - tuberculosis
- Do not stain Gram-positive
- Very slow growth
- High antibiotic resistance

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16
Q

Mycobacterium: Cell envelope

A
  • Waxy coating over peptidoglycan, inc. mycolic acids
  • Extremely hydrophobic; slows the uptake of many antibiotics and nutrients
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17
Q

Mycobacterium Cell envelope

A

~ Analogous to an outer membrane (yet much thicker)
- Includes (some) aqueous channel proteins with similarities to *porins

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18
Q

Proteobacteria (Pseudomonadota)

A
  • Gram-negative (i.e. with outer membrane)
  • Range from largest prokaryotes to tiny ‘parasites’
  • Metabolically extremely diverse, include various…
  • Organotrophs
  • Lithotrophs
  • Phototrophs
  • Major phylogenetic groups include: Alpha-, Beta- & Gamma-proteobacteria
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19
Q

Enteric bacteria - example organotrophic (Gamma)proteobacteria

A
  • Diverse: over 40 genera
  • Facultative anaerobes:
    • can respire via nitrate reduction
    • can also ferment various sugars**
  • Most associate with animal hosts, especially the intestinal tract
  • Many are (or can be) pathenogenic
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20
Q

MacConkey Medium

A

Example of a differential medium that distinguishes bacteria by their fermentative abilities: indicates whether acid is produced or not, lactose fermenting?

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21
Q

Eschericihia coli (E. coli)

A
  1. Probably best studied bacterial species
    - Basic biochemistry and cell biology
    - Mainstay of molecular cloning
  2. Inhabits intestinal tracts of many animals
  3. Indicator organisms for testing water for fecal contamination
22
Q

Pseudomonads

A

Facultative anaerobes:
- (limited fermentation abilities)
- Anaerobic respiration with various alternative electron acceptors, including denitrification
e.g. Pseudomonas aeroginosa
- Found on soil, but also facultative pathogen:
- burn wounds, lungs (esp. in cystic fibrosis)

23
Q

Example Lithotrophic Proteobacteria

A
  • Sulfur oxidizers
  • Nitrifiers
24
Q

Gammaproteobacteria sulfur

A

Many large sulfur/sulfide oxidisers belong to gammaproteobacteria: Beggiatoa, Thiomargarita

25
Q

Nitrifiers

A

Tow sorts:
1. Ammonia (NH3) oxidosers: NH3 -> NO2 (nitrite)
2. Nitrite oxidisers: NO2 -> NO3 (nitrate)

  • High reduction potentials (= poor electron donors)
    *Clasiccally, aerobes..
    Betproteobactera (for example) includes several nitrifiers
26
Q

Nitrogen Cycle

A

(See slides)

27
Q

Nitrogen fixation (N2 -> NH4)

A
  • Energetically expensive
  • Certain Bacteria and Archaea *only
  • Ocean: 40-80% of the world total; mostly Cyanobacteria?
  • Soil: Alphaproteobacteria important
  • In symbiotic associations with certain plants: esp. *Rhizobia (Alphaproteobacteria again)
28
Q

Nitrogen fixation and O2

A
  • Nitrogen fixation enzyme complex (nitrogenase) inactivated by oxygen:
    • Problem for aerobic nitrogen fixers

Some coping strategies:
- Facultative anaerobes often fix nitrogen only under anaerobic conditions
- Cyanobacteria: Fix N2 at night, or in thick-walled non-photosynthetic cells: ‘Heterocysts’
- Leghemoglobin in rhizobia nodules

29
Q

Rhizobia

A
  • Type of Alphaporteobacteria
  • Organotrophic aerobes
  • Live freely on soil, but also infect roots of legumes
    • peas, beans, clover, etc
  • Nodules: plant cells contain rhizobia, mostly as “bacteroids”
  • The enlarged “bacteroids” fix nitrogen, benefitting plants
30
Q

Rhizobia-Legume Symbiosis

A
  • Plant provides reduced organic compounds
  • Plant receives fixed nitrogen (NH4)
  • *Leghemoglobin in nodule binds O2 to maintain low concentration of free O2
31
Q

Bdellovibrio

A
  • Predator of other Gram-negative bacteria
32
Q

Nitrification, Denitrification, and Nitrogen fixation

A
  1. Nitrification: N compounds oxidized, yields energy (lithotrophy; usually aerobic)
  2. Denitrification: N compounds reduced, yields energy (anaerobic respiration; typically organotrophic)
  3. Nitrogen fixation: N reduced, costs energy (feeds into biosynthesis)
33
Q

Phototrophy

A
  • Conversion of light energy into chemical energy (+ storage as organic molecules = photosynthesis)
  • Microorganisms are globally important photosynthesizers (especially in water)
  • Two different systems in prokaryotes, based on:
    1. Chlorophyll (Chl) or Bacteriochlorophyll (BChl)
    2. Retinal (in bacteriorhodopsin)
34
Q

Retinal-based phototrophy (Bacteriorhodopsin)

A
  • Light-driven proton (H+) pump, in cell membrane
  • makes proton motive force, driving ATP synthesis
35
Q

Retinal-based phototrophy (Bacteriorhodopsin)

A
  • Supplementary ATP synthesis for heterotrophs
  • In some Bacteria (e.g. some Porteobacteria)
  • But also some Archaea (Holoarchaea)
36
Q

(Bacterio)chlorphyll-based systems in a nutshell

A

= Phton capture excites an electron (so, a poor electron donor becomes a good electron donor)

37
Q

Cyclic Photophosphorylation:

A
  • Energy from electron transfer in ETS harnessed to generate proton motive force (PMF)
  • PMF -> ATP synthesis (as in respiration)
  • Electrons eventually return to excitable molecule
38
Q

Non-cyclic flow

A
  • Electrons transferred to a carrier (e.g. NADP+) & used for biosynthesis (e.g. CO2 fixation)
  • Electrons replaced from external electron donor (‘Photolysis’ of external donor)
39
Q

Some generalities about Chl/BChl-based phototrophy

A
  • A membrane-localised process

Light-harvesting Antenna system…
- Chlorophylls (Chl)/Bacteriochlorophylls (BChl)
- Plus accessory pigments

-… transfers harvested energy to Reaction centre: inc. ‘reaction centre chlorophyll/ bacteriochlorophyll’

  • Electron-transport system (ETS) transfers excited electrons to energy carriers
    (or returns them to reaction centre Chl/BChl)
40
Q

Properties of purple bacteria (proteobacteria)

A

Main Chlorophyll: Bacteriochlorophylls (BChl)

Main accessory pigments:
Carotenoids

Photosystems:
One; PS II -like

Typical external Electron donor:
H2S, Sulfur or organic

41
Q

Green sulfur bacteria (Chlorobiota) properties

A

Main Chlorophyll:
Bacteriophyllus (BChl)

Main Accessory pigments:
Carotenoids

Photosystems:
One: PS I -like

Typical external Electron donor:
H2S, Sulfur

42
Q

Cyanobacteria Properties

A

Main Chlorophyll:
Chlorophyll a (Chl a)

Main Accessory pigments:
Phycobilins (& carotenoids)

Photosystems:
Two: PS I & II

Typical external Electron donor:
H2O (-> O2) (Oxygenic) (only oxygenic prokaryotes; all other prokaryotic photosynthesisers are ‘anoxygenic’

43
Q

Cellular absorption spectra

A

1) Bacteriochlorophylls absorb longer wavelengths (red/infrared) then chlorophylls
2) Accessory pigments (e.g. carotenoids) extend organism’s absorption spectrum

44
Q

Examples of Photosynthesis with one photosystem

A

Green sulfur bacteria (Chlorobiota) & Purple bacteria

45
Q

Phototrophic Proteobacteria

A

Mostly “purple bacteria”
- ‘Purple Sulfur’: autotrophs photolysing H2S to Sulfur (S0) as I ‘green sulfur bacteria’
- ‘Purple non-sulfur’

46
Q

Purple non-sulfur bacteria

A

often “part-time” phototrophs, e.g.:
- Aerobic conditions: organotrophs
- Anaerobic conditions: phototrophs

Mostly Photoheterotrophs
= energy from phototrophy used (in part) to modify *existing organic molecules, NOT to fix CO2

47
Q

Evolution of photosynthesis

A
  • Simpler *anoxygenic photosynthesis evolved first
  • Oxygenic two-photosystem photosynthesis:
    • PSI resembles green sulfur bacteria PS
    • PSII similar to purple bacteria PS
    • ‘Combines’ by *horizontal gene transfer

~ 2.6 BYA - Oxygen begins to accumulate

Later: Oxygenic photosynthesis acquired by eukaryotic lineage by *endosymbiosis

48
Q

Cyanobacteria (formerly: ‘blue-green algae’)

A
  • Most abundant & diverse group of photosynthetic prokaryotes
  • gram-negative cell envelope; but usually with *thick cell wall
  • Never with flagella; but may have ‘gas vesicles’, or glide, for motility
  • 2 Photoystems; oxygenic
  • Autotrophs
49
Q

Photosynthetic apparatus (cyanobacteria)

A
  • Thylakoid membranes
  • Chlorophyll a
  • Major accessory pigments: (Phycobilins) in ‘Phycobilisomes’ or thylakoids**
50
Q

Diversity of Cyanobacteria

A
  • > 50 genera, cells range <1 micrometres to >40 micrometres
  • Many filamentous; may differentiate into 2+ cell types
  • Thick sheaths/mucus layers in some taxa
51
Q

Gas vesicles

A
  • thin *protein shell excludes water: gas can accumulate
  • Function: buoyancy vertical movement in water column
  • In some prokaryote groups, mostly phototrophs
    • especially Cyanobacteria
52
Q
A

Diversity of Plants and Microorganisms (2 decks)

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