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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
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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)

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23
Q

Example Lithotrophic Proteobacteria

A
  • Sulfur oxidizers
  • Nitrifiers
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24
Q

Gammaproteobacteria sulfur

A

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

25
Nitrifiers
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
Nitrogen Cycle
(See slides)
27
Nitrogen fixation (N2 -> NH4)
- 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
Nitrogen fixation and O2
- 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
Rhizobia
- 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
Rhizobia-Legume Symbiosis
- Plant provides reduced organic compounds - Plant receives fixed nitrogen (NH4) - *Leghemoglobin in nodule binds O2 to maintain low concentration of free O2
31
Bdellovibrio
- Predator of other Gram-negative bacteria
32
Nitrification, Denitrification, and Nitrogen fixation
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
Phototrophy
- 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
Retinal-based phototrophy (Bacteriorhodopsin)
- Light-driven proton (H+) pump, in cell membrane - makes proton motive force, driving ATP synthesis
35
Retinal-based phototrophy (Bacteriorhodopsin)
- Supplementary ATP synthesis for heterotrophs - In some Bacteria (e.g. some Porteobacteria) - But also some Archaea (Holoarchaea)
36
(Bacterio)chlorphyll-based systems in a nutshell
= Phton capture excites an electron (so, a poor electron donor becomes a good electron donor)
37
Cyclic Photophosphorylation:
- 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
Non-cyclic flow
- 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
Some generalities about Chl/BChl-based phototrophy
- 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
Properties of purple bacteria (proteobacteria)
Main Chlorophyll: Bacteriochlorophylls (BChl) Main accessory pigments: Carotenoids Photosystems: One; PS II -like Typical external Electron donor: H2S, Sulfur or organic
41
Green sulfur bacteria (Chlorobiota) properties
Main Chlorophyll: Bacteriophyllus (BChl) Main Accessory pigments: Carotenoids Photosystems: One: PS I -like Typical external Electron donor: H2S, Sulfur
42
Cyanobacteria Properties
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
Cellular absorption spectra
1) Bacteriochlorophylls absorb longer wavelengths (red/infrared) then chlorophylls 2) Accessory pigments (e.g. carotenoids) extend organism's absorption spectrum
44
Examples of Photosynthesis with one photosystem
Green sulfur bacteria (Chlorobiota) & Purple bacteria
45
Phototrophic Proteobacteria
Mostly "purple bacteria" - 'Purple Sulfur': autotrophs photolysing H2S to Sulfur (S0) as I 'green sulfur bacteria' - 'Purple non-sulfur'
46
Purple non-sulfur bacteria
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
Evolution of photosynthesis
- 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
Cyanobacteria (formerly: 'blue-green algae')
- 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
Photosynthetic apparatus (cyanobacteria)
- Thylakoid membranes - Chlorophyll a - Major accessory pigments: (Phycobilins) in 'Phycobilisomes' or thylakoids**
50
Diversity of Cyanobacteria
- >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
Gas vesicles
- thin *protein shell excludes water: gas can accumulate - Function: buoyancy vertical movement in water column - In some prokaryote groups, mostly phototrophs - especially Cyanobacteria
52
Filaments with differentiation (Heterocysts and Akinetes)
Heterocysts: specialized *nitrogen-fixing cells - In one particular subgroup; example *Anabaena - Thick wall excludes O2, and... - No photolysis of H2O -> O2 (no photosystem II) Akinetes: large, resistant cells; dormancy stage
53
Ecology of Cyanobacteria
Hugely important in *open ocean - Primary production (new organic C) + Oxygen - (esp. very *small forms: e.g. Prochlorococcus) - Nitrogen fixation Lake: blooms (sometimes toxic) in nutrient-rich lakes Surface sediments, some in soils Symbiotic relationships (e.g. with fungi -> lichens**)
54
Cyanobacteria examples
- Planktonic Prochlorococcus (Concentrated: fluorescent probe) - Lichen with cyanobacterial photobiont - "Mare's egg"
55
Spirochaetes/spirochetes (Spirochaetota)
- Long, thin, flexible cells with a spiral shape - Periplasmsic space contains the flagella - Organotrophs - *Many are symbionts or parasites - agents causing syphilis & Lyme disease - termite symbionts, including nitrogen-fixers - e.g. Spirochetes (& other prokaryotes) from termite hindgut
56
Spirochaete cell structure
- Most of cells forms a helical 'protoplasmic cylinder' - 'Outer sheath' includes outer membrane; flexible - 2-100+ flagella; in two bundles
57
Locomotion
- Flagellar rotation creates tosion to counter-rotate protoplasmic cylinder - Protoplasmic cylinder 'screws' through medium
58
Other bacteria groups (Thermophiles)
- Aquificota (e.g. aquifex) - Thermotogae - Deinococcus-Thermus - Chloroflexi
59
Aquifec and Thermotoga
- e.g. In geothermal pools; smoldering coal-mine waste Include the most thermophilic (heat-loving) Bacteria - Aquifex 'aeolicus': optimal growth at 85 degrees - Yet many ARCHAEA are even more thermophilic!

Diversity of Plants and Microorganisms (6 decks)

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