week 11 - Cyanobacteria

Question 1

Cyanobacteria:
- Oxygenic phototrophs

Answer 1

o Most species are obligate phototrophs (use light)
o Important in producing O2 in the early atmosphere
 Allowed other life to develop (more O2 in atmosphere)

• Found in terrestrial, freshwater, and marine habitats
  o Can form extensive crusts in desert soils
  -

Question 2

Cyanobacteria:
- Morphologically diverse

Answer 2

o Unicellular and filamentous forms

Question 3

Cyanobacteria:
- Many cyanobacteria produce potent neurotoxins

Answer 3

o Can cause poisoning during blooms (grow to high concentrations

Question 4

Cyanobacteria:
- Found in terrestrial, freshwater, and marine habitats

Answer 4

o Can form extensive crusts in desert soils

Question 5

Photosynthesis in cyanobacteria
- Thylakoids

Answer 5

o Intracellular membrane
o Location of protein complexes involved in photosynthesis and respiratory electron transport chains

Question 6

Photosynthesis in cyanobacteria
- light harvesting pigments

Answer 6

o Phycobilins (accessory pigment)
 Blueish colour
o Chlorophyll a
 Green colour
o Cyanobacteria referred to as blue-green algae
o Have a common ancestor with the endosymbiont that gave rise to chloroplasts

Question 7

endosymbiosis

Answer 7

• Theory to explain how eukaryotes gained mitochondria and chloroplasts
• Predicting they were once free living prokaryotes
• ~ 2 billion years ago
• Mitochondria  alpha-proteobacteria phylum
• Chloroplasts  cyanobacteria phylum
• The symbiotic relationship was then selected for and lead to a huge expansion of Eukaryotic diversity

Question 8

CYANOBACTERIA:
cell envelope

Answer 8

o Peptidoglycan in cell walls
o Outer and cytoplasmic membranes
o Mucilaginous envelopes/sheaths
o form clusters of cells

Question 9

CYANOBACTERIA:
gas vesicles

Answer 9

o help maintain buoyancy
o keep cell in water column where there is light

• Not specialised
• Cylinder shaped
• How do they control buoyancy
  o Pressure from photosynthesis
  o High pressure cause vesicles to collapse
  o sink

Question 10

CYANOBACTERIA:
differentiated cell type

Answer 10

• some filamentous cyanobacteria have a differentiated cell type
  o heterocyst

Question 11

CYANOBACTERIA:
motility

Answer 11

• many cyanobacteria display gliding motility

Question 12

CYANOBACTERIA:
heterocysts

Answer 12

• Specialised cell type
• Rounded, enlarged cells
• Connected to adjacent vegetative cells
• Anoxic (low O2 environment) environment inside heterocyst
  o Site for nitrogen fixation
   can fix inorganic nitrogen
  o nitrogenase is sensitive to oxygen
• part of functioning string of bacteria

Question 13

Lichen

Answer 13

• Symbiosis between a fungus and a phototrophic organism
  o Algae or cyanobacteria
  o Often cyanobacteria that can fix N2
  o Fungus gains organic matter from photosynthesis
  o Bacterium (or alga) gains anchorage, water and inorganic nutrients, protection from desiccation