Cyanobacteria Flashcards
What are cyanobacteria also commonly known as?
Blue-green algae
What distinguishes cyanobacteria from other prokaryotes?
They are the only photosynthetic prokaryotes that produce oxygen
What gives cyanobacteria their characteristic color?
The pigment phycocyanin
What type of cell wall do cyanobacteria have?
Peptidoglycan-based, Gram-negative
When did cyanobacteria begin oxygenating Earth’s atmosphere?
Around 2.5 billion years ago
What are stromatolites and why are they significant?
Rock-like structures formed by cyanobacteria; Earth’s oldest fossils
How did cyanobacteria contribute to the evolution of eukaryotes?
Through endosymbiosis, becoming the ancestors of chloroplasts
What photosystems do cyanobacteria use?
Both PSI and PSII
What pigments are found in cyanobacteria?
Chlorophyll a, phycobilins (phycocyanin and phycoerythrin), and sometimes divinyl chlorophylls
How do cyanobacteria produce energy at night?
Through aerobic respiration or fermentation of stored carbon like glycogen
What is photoheterotrophy in cyanobacteria?
The use of light for energy while using organic carbon sources
Do cyanobacteria have flagella?
No, they move via gliding motility.
What structures help cyanobacteria control buoyancy?
Gas vesicles
What are akinetes?
Resting cells with thick walls that protect against harsh conditions
What are hormogonia?
Short motile filaments for dispersal under stress
Why is nitrogenase sensitive to oxygen?
Because O₂ inhibits nitrogen fixation
What are heterocysts?
Specialized, thick-walled cells that create anoxic environments for nitrogen fixation
How do heterocysts differ from vegetative cells?
They lack PSII and cannot fix CO₂, but receive carbon from neighboring cells
What percentage of marine photosynthesis do Synechococcus and Prochlorococcus contribute?
About 80%
Why are cyanobacteria critical in nitrogen-limited ecosystems like the Arctic?
They can fix atmospheric nitrogen, contributing up to 80% of annual input
Name two cyanobacteria adapted to extreme environments
- Nostoc
- Trichodesmium
What is special about Synechococcus?
Unicellular, widespread in oceans, a major contributor to oceanic primary production
What is unique about Prochlorococcus?
Smallest, most abundant photosynthetic organism on Earth, with unique chlorophylls
What’s notable about Trichodesmium?
Fixes N₂ without heterocysts, has gas vesicles, thrives in tropical seas
