Cyanobacteria

Question 1

key features of cyanobacteria

Answer 1

• No nucleus (dna is circular and free-floating in the cytosol
• Photosynthetic machinery : thylakoids house pigments and proteins for photsynthesis , unlike eukaryotes thylakoids are not enclosed in chloroplasts and remain single, not stacked.
• Movement: some are immotile whle others use gliding motility
• Reproduction only produce by binary fission or fragmentation

Question 2

main pigments

Answer 2

• Chlorophyll a
• Phycobilins
• (Phycocyanin, Phycoerythrin , Allophycocyanin, Carotenoids)

Question 3

storage products

Answer 3

• Excess photosynthate (startch) stored as cyanophycean starch
• Nitrogen stored as cyanophycin granules
• Phosphate stored in polyphosphate granules

Question 4

reproduction

Answer 4

• Only asexual
• Repid growth and survival
• Akinetes, such as those produced by Nostoc, are dormant resilient spores which can germinate in suitable contitinos to produce a new filament.

Question 4

cyanobacteria and nitrogen fixation

Answer 4

• Biochemical process of capturing and converting atmosphereic nitrogen gas into usable organic nitrates such as ammonia which can be used by plants and other organisms
• Cyano bacteria are the only organisms able to perform both oxygenic(oxygen generating) photosynthesis and nitrogen fixation
• Allows cyanobacteria to thrive in nitrogen limited environments and enrich ecosystems
• Vegetative cells carryout photosynthesis whilst specialized cells called heterocysts carry out nitrogen fixation called heterocycs

Question 5

what are akinetes

Answer 5

 Most filamentous cyanobacteria develop perennating structures (dormant structures)in adverse condition.
* These structures are larger specialised, thick- walled dormant resting cells that protect the organism in unfavourable conditions
* Spores released when cell ruptures
* When favourable conditions return, they germinate and produce new filaments.
* It serves as a survival structure (resting cell)

Question 6

what is hormogonia

Answer 6

Hormogonia
- All filamentous cyanobacteria reproduce by fragmentation of their filaments to form short pieces each consisting of 5-15 cells.
- These sort motile pieces of filament are called hormogonia
- The latter show gliding motility and develop into new full fledged filaments

Question 7

flagella

Answer 7

none

Question 8

morphology

Answer 8

prokaryotic, unicellular, aggregates, colonial, filamentous, heterocystis

Question 9

plastids

Answer 9

not present (prokaryotic)

separate thylakoids with granular phycobilisomes located on the outer surface

Question 10

cell covering

Answer 10

4 layered -
contain lysozyme- digestible mucopolymer layer, muramic acid glucosamine, alanine and glutamic and diamino-pimelic acids. some species covered by mucilagenous sheath

Question 11

No. of sp

Answer 11

around 2000

Question 12

habitat

Answer 12

Marine, freshwater and terrestrial, found in soild hotsprings and sal lakes. planktonic, benthic, epiphytic