Cyanobacteria Flashcards
2 dominant kinds of phototrophs based on their source of carbon
- Photoautotrophs (fix CO2)
- Photoheterotrophs (use organic carbon)
Cyanobacteria characterisitcs
- gram negative
- Mostly oxygenic photoautotrophs
- Diverse morphologies
- Account for 1/4 of all biomass production on earth
Prochlorococcus
single-celled cyanobacteria
* most abundant phototroph in oceans
What do Oscillatoria, Nostoc, and Anabaena all have in common
all filamentous bacteria
what are the spores called that many cyanobacteria form
akinetes
what was responsible for the Great Oxidation Event
Photosynthesis by Cyanobacteria
Great Oxidation Event
Start of the rapid oxidation of earths atmosphere - dramatic increase in oxygen on earth
* major changes in planet
* Oxygen was toxic to most microbes
* This led to first mass extinction
What structures are a major clue of the Great Oxidation Event
Stromatolites
Four major categories of prokaryotic microbes found in stromatolites
- Cyanobacteria
- prokaryotes of uncertain systematic relations (unsure)
- Sulphate-reducing bacteria
- Methane-producing archaeans
How does cell size and morphology of cyanobacteria compare to other prokaryotes
Have larger cells and more complex morphology = easier to recognize = best documented fossil records
2 different hypotheses about mutlicellularity and the GOE
- Multicellularity before the GOE due to high abundance of cyanobacteria = high O2
- Multicellualrity arose after GOE as asaptation to newly oxidized habitats
Conventional classification of cyanobacteria (section 1-5)
Section I: unicellular, binary fissuon
Section II: unicellular, binary/multiple dission, form baeocytes
Section III: filamentous, non-heterocystous
Section IV: filamentous, heterocysts devlop during nitrogen starvation
Section V: filamentous, in absense of nitrogenous source heterocysts develop
Example of Cyanobacteria classified as section I and why
Synechococcus sp. - can divide by binary fission
Example of Cyanobacteria classified as section II and why
Pleurocapsa sp. - divide by multiple fission and develop Baeocytes (small cell that will grow and become a vegetative cell)
Are cyanobacteria gram -
What might differentiate them
Yes and no..
* two membranes AND a thick peptidoglycan layer (S-layer like gram +)
What are cyanobacterial blooms
- Harmful algal blooms”
- happens in bodies of water
Three factors that help development of and maintaining bacterial blooms
- factors concur to such cyanobacterial proliferation, such as high nitrogen and phosphorus content
- light intensity and temperature trends (climate variations)
- Eutrophication (excess of nutrients)
Nodularia spumigena and cyanobacteria blooms
- type of cyanobacteria that creates blooms
- more toxic when theres little nitrogen in the water but sufficient amount of phosphorus
What are cyanotoxins
“harmful agents” (e.g. Microcystin, Nodularins) produced by cyanobacteria
* they can be aljaloids, non-ribosomal peptides, polyketides, non-protein amino acids, indole alkaloids, oragnophosphates, lipopeptides, and lipoglycans
What do cyanotoxins provide to cyanbacteria
provide competitive advantage
how might organisms be exposed to cyanobacterial toxins
drinking, bathing in, or inhaling contaminated water
Consequences of exposure to cyanotoxins
inflammation, immune disorders, oxidative stress, and ROS
Cyanotoxin abbreviated NOD
Nodularins
* pentapeptides (5 amino acids)
What type of toxin in the cyanotoxin Nodularins (i.e. where in the body does it effect)
Hepatotoxin (liver)
What cyanobacteria produces the toxin Nodularins
Nodularia Spumigena
Stability of Nodularins (NODs)
very stable: it will not degrade as a result of light, temp, and microwaves
What can we do to avoid contact with cyanotoxins
- Monitoring via Satellite Imagery.
- Cyanobacteria identification -> is it a cyanotoxin producer?
- Cyanotoxin identification (i.e. ELISA, UHPLC, etc.)
- Zonification is important. Avoid water contact.
- Ensure adequate water treatment.
Microbial mat
layered community of microorganisms found in aquatic environments
Microbial mats are formed by multiple ____ of microorganisms embedded in a matrix of ________________, in a vertical fashion due to the physical gradients
biofilms; exopolysaccharides (EPS)
Thickness of microbial mats
ranges from millimeters to several centimeters
Microbial mats are commonly associated with what habitats
aquatic habitats, including hot springs, hypersaline ponds, and intertidal coastal zones and oligotrophic enviornments (low levels of nitrogen)
Layers of microbial mats and what they do
- Scytonemin -> photoprotective pigment (UV radiation)
- Cyanobacteria -> photosynthesis
- Bacteria below cyanobacteria -> low O2 levels
layer of green sulphur bacteria has been observed in only a few occasions
how do microbial mats work together
- microorganisms interact and exchange signals
- embedded in a matrix of exopolysaccharides and nutrients to enable a greater flow of resources and energy for the survival of the community
Describe the layered community of a microbial mat (diagram from lecture) in respect to metabolic byproducts and the infiltration biofilms (EPSs)
- Cyanobacteria = oxygenic phototrophs: use sunlight to convert carbon dioxide into organic matter (CH₂O) and oxygen
- oxygen produced by cyanobacteria creates an aerobic zone that can be utilized by aerobic heterotrophs
- Cyanobacterial organic material byproduct (CH2O) is used by aerobic heterotrophs, anoxygenic phototrophs, and anaerobic heterotrophs
to avoid grazing where do microbial mats colonize? has it always been this way?
colonize in “extreme environments” - i.e. hot springs and hypersaline pools where the slow growing microbial mats wont be disrupted
* in the past they colonized in all places (stromatolites)
Biocrusts
community of living organisms on the soil surface in arid or semi-arid systems
What are biocrusts typically composed of
cyanobacteria, fungi, lichens, bryophytes, and algae
ecological function of biocrusts
soil stability
4 types of biocrusts
- smooth/flat
- Rugose
- Pinnacled
- Rolling
Characteristics of smooth/flat biocrusts
- dominated by cyanobacteria
- hyperarid regions
- high PET (potential evapo-transpiration)
- Cannot support lichens or mosses (why its flat)
Characteristics of rugose biocrusts
- up to 3 cm
- High PET deserts (potential evapo-transpiration)
- Minimal lichen, moss coverage
Characteristics of Pinnacled Biocrusts
- up to 15 cm
- occur in moderate PET deserts (potential evapo-transpiration)
- Lichen cover is <40%
- Soils freeze in winter
Characteristics of rolling crusts
- Found in cool to cold deserts
- low PET (potential evapo-transpiration)
- soils freeze
- Restricted to about 5cm-7.5cm
What is false about microbial mats and biocrust?
a) Both are composed of microbial communities.
b) Cyanobacteria play a significant role in both.
c) They exhibit similar structural formations.
d) Microbial mats primarily form in aquatic environments
c) They exhibit similar structural formations.
What is the dominant organism shown in this soil surface after crust formation
What do they go?
- spherical, large, multicellular, Cyanobacteria, Nostoc group
- fix nitrogen from the atmosphere thus allowing succession of other life forms
life cycle of heterocyst-forming cyanobacteria (Such as Nostoc): what is formed in…
* low nitrogen (deprivation)
* high nitrogen
* energy-limiting conditons
- low nitrogen (deprivation) = heterocysts
- high nitrogen = just vegetative cells
- energy-limiting conditons = akinetes
- can also produce Hormogonia (dispersal forms) in certain condtions
ALL interconnected
Cyanobacteria can fix both Nitrogen and CO2 - how?
Cellular differentiation
* Heterocysts fix atmospheric nitrogen
* Vegetative cells fix CO2
3 specialized cells of* Nostoc* & what they do
- Akinetes: Dormant specialized cell (unfavorable conditions). germinates as new vegetative cells, allowing the organism to resume growth and reproduction.
- Heterocyst: Nitrogen fixation
- Hormogonia: For dispersal
(favorable conditions for symbiosis). They are filaments of cells, and can stablish new colonies.
When Nostac clumbs together what does it form
Nostac forms filaments that clump together in large balls of mucilage
Cyanobacteria as food
Nostoc commune “Llullucha” or “cushuro” in Peru
* yummy but contain BMAA = neurotoxin
* Nitrogen fixers so good source of protein
Habitat of Nostoc balls
inhabits high altitudes and thrives in low temps with high UV radiation
* Atacama Desert, Chile
* Oligotrophic locations with tadpoles
Role of exopolysaccharides (EPSs) in cyanobacteria
- adhesion
- structure
- protection against a-biotic stresses (water stress, UV stress, physical and chemical stresses)
- bioweathering processes
- gliding motility
- nutrent repositories
Which is true about Nostoc sp.:
a) Heterocysts are specialized cells for the survival of Nostoc during unfavorable conditions.
b) Scytonemin is responsible for nitrogen fixation.
c) Vegetative cells have Nitrogenase.
d) Scytonemin is a photoprotective pigment against harmful UV radiation.
d) Scytonemin is a photoprotective pigment against harmful UV radiation.
