Cyanobacteria II Flashcards
What are thylakoids and what pigments do they have
- these are in cyanobacteria
-they are free floating membranes that are the site of photosynthesis - they contain chlorophyll a and accessory pigments that aid in light harvesting for photosynthesis
- they contain chlorophyll reactive centers where most photosynthesis occurs and accessory pigments which help the chloroplast reactive centers gather as much solar light as possible for photosynthesis
- they are concentrated towards the outside of the cell
What are thylakoids embedded with
they are embedded with photosystems that consist of xanthophylls (accessory pigments) that surround a reaction center containing only chlorophyll a
Which groups have phycobilosomes
only cyanobacteria and red algae have these
Describe phycobilisomes
these dot the thylakoids and contain water soluble accessory pigments consisting of proteins termed phycobilin’s
–> depending on which type of phycobilisome a cyanobacteria produces, it will be better at absorbing diff. wavelengths of light available.
What do phycobilisomes do with photons
photons will hit the phycobilisomes which will then adjust the energy of that photon to make it exactly the energy level required to optimally energize the chlorophyll molecule. So if the photon comes in too fast or too high energy they phycobilisome will slow it down
What are the 3 phycobilin’s
Allophycocyanin, phycocynanin, phycoerythrin (on the very outside)
What is the name of the process that the phycobilisomes in the thylakoid membrane do
Resonance transfer - this is where the energy of the captured photons is adjusted to the optimal level to oxidize Chl a and initiate the electron flow from the reaction center (photon goes through 3 phycobilin levels: phycoerytherin, then phycocyanin, and then allophycocyanin)
Describe the wavelength at which phycobilins absorb sunlight
they absorb sunlight at different wavelengths than chlorophyll do and also at different wavelengths than other carotenoids found in other algae –> so this gives cyanobacteria a competitive advantage in aquatic environments where that mid wavelength light happens to be the most abundant
Which of the 3 phycobilins absorbs the higher energy light
phycoerethrin
What allows for the differential light absorption profiles of cyanobacterial pigments
the positioning of the double conjugated carbon bonds determine light absorption characteristics
What is the process called where phycobilin concentration of cyanobacteria is adjusted to different light environments
chromatic acclimation
Describe the chromatic acclimation of cyanobacteria to clear waters
- With a clear lake the shorter wavelengths penetrate down further and the longer ones get attenuated near the surface
- A cyanobacterial cell at the bottom would primarily see blue light and so they need to absorb this blue light
- cyanobacteria switch their production of phycobilin’s to phycoerythrin red pigments (so red light is reflected and blue light is absorbed)
- so in deep clear water phycoerythrin production by blue/green algae is very pronounced giving them a reddish appearance
Describe the chromatic acclimation of cyanobacteria to brownish water like in Bogs
- solar irradiance is attenuated very rapidly in brownish waters
- organic bacteria absorb the sunlight and most of the high energy sunlight like blue is rapidly attenuated
- what penetrates to the bottom is red light
- in this case phycobilin production is switched to phycocyanin which absorbs the red light and reflects blue light making the pigment look more blueish
Describe the chromatic acclimation of cyanobacteria to turbid waters like that of a glacial lake
- here there is intermediate light penetration (mid range of the visible light spectrum photons are getting through)
- here allophycocyanin optimizes the photons best (phycoerytherin wouldn’t do well because there isn’t a lot of blue light here, phycocyanin wouldn’t do well because there isn’t a lot of red light either)
Describe they buoyancy conveyor belt of cyanobacteria
high photosynthate content of cyanobacteria in surface waters collapses aerotopes causing them to sink overnight into sediments where nutrient uptake is the possible, so at night cyanobacteria take up nutrients from the bottom of the lake, they are respiring and losing organic carbon, so cell pressure is starting to weaken and cells start to rise again with gas vesicles becoming inflated.
