cyanobacteria

Question 1

oxygen revolution/ great oxygenation event

Answer 1

2.7 - 2.2 billion years ago
O2 in atmosphere generated photosynthetically by cyanobacteria
cyanobacteria as first organisms to use H2O as source of electrons and hydrogen to fix CO2

Question 2

primary endosymbiosis

Answer 2

origin of eukaryotic plastids through cyanobacteria
oxygenic photosynthesis only evolved once in cyanobacteria
all photosynthetic eukaryotes got ability to photosynthesize from them
eukaryotic cell engulfed free cyanobacterium
now as double-membraned chloroplast (Primary endosymbiont)

Question 3

importance of cyanobacteria

Answer 3

first photosynthetic organisms to evolve on the planet
responsible for producing an oxygenic atmosphere
biogeochemical cycling (carbon and nitrogen)
nitrogen fixers
component of marine food webs
bioindicators
gave rise to eukaryotic plastids - endosymbiosis
important symbionts in many eukaryotes (lichens, etc.)
economic wealth for food, supplements, etc
toxic blooms

Question 4

how many cyanobacteria

Answer 4

about 150 genera with 2000 species

Question 5

how old are cyanobacteria

Answer 5

2.7 to 2.3 billion years old
stromatolites as living fossils

Question 6

where are cyanobacteria found

Answer 6

almost every terrestrial and aquatic habitat
symbiotic
hot springs

Question 7

cellular structure of cyanobacteria

Answer 7

true bacteria, prokaryotic
simple cellular construction
lack nuclei and membrane bound organelles
DNA, cytoplasm, plasma membrane, and ribosomes

Question 8

photosynthetic pigments

Answer 8

chlorophyll a
accessory –> phycolbilins (phycoerythrin, phycocyanin), carotenoids (xanthophylls, and B-carotene)
only specific colors are absorbed
arranged in pigment-protein complexes (phycobilisomes)

Question 9

chlorophyll a

Answer 9

reaction sensor photosynthetic pigment

Question 10

accessory pigments

Answer 10

harvest energy down to chlorophyll a

Question 11

where are pigments

Answer 11

phycobilisomes embedded into folds in thylakoid membranes, scattered through the cytoplasm
act as light harvesting antennae for photosystems
higher wavelengths absorbed first and all energy is passed to chlorophyll a

Question 12

growth forms of cyanobacteria

Answer 12

unicellular
colonial
filamentous
occurs only at the cell level when they divide

Question 13

structure of cyanobacteria

Answer 13

all types surrounded by mucilaginous (nonpigmented) sheath made of polysaccharides
sheath thickness varies

Question 14

importance of sheath on cyanobacteria

Answer 14

used for protection from desiccation, temperature, UV, etc. in environment
metabolism

Question 15

cyanobacteria diversity

Answer 15

some species as unicells, unicells may become colonies
aggregations of cells into “trichomes” or filaments —> linear stacks of cells within colorless sheath
specialized structures

Question 16

heterocysts

Answer 16

highly refractive cells with thickened cell walls
larger in size than other cells
usually unpigmented/ pale or translucent (no photosynthetic pigments)
contain the enzyme nitrogenase
cyanobacteria are able to make nitrogen useable by other organisms with these cells (nitrate and ammonium can be absorbed to convert into protein and nucleic acids)

Question 17

nitrogenase

Answer 17

enzyme that catalyzes the fixation of N2 to NO3/NH4 (atmospheric into nitrate or ammonium)

Question 18

akinetes

Answer 18

asexual spores
ofetn larger and appear granulated
drought resistant
produced by vegetative cells
develop a thickened cell wall
filled with cyanophycin
stain darkly
often adjacent to heterocysts
released from cyanobacteria and can remain dormant for long periods of time —> overwintering
can survive unfavorable conditions
germinate to form a new individual

Question 19

cyanophycin

Answer 19

what akinetes are filled with
starch-like storage compound

Question 20

false branching

Answer 20

filament divides in half and continues to grow in both directions
rupture of sheath and cells
remaining cells at both ends continue to grow
both trichomes push through weakened sheath
parallel to main axis

Question 21

true branching

Answer 21

change in plane of cell division
stay attached to colonies
no rupture of sheath or cells
create new structures, branches
perpendicular growth

Question 22

cyanobacteria reproduction

Answer 22

asexual reproduction
can be fission, fragmentation,akinetes (internal and external), endo- or exo- spores
unicellular forms have fission while filamentous multicellular forms exhibit fragmentation
genetic recombination reported in some species

Question 23

binary fission

Answer 23

cell division for unicells and colonial forms
produces genetically identical “offspring” or twins
increases # of cells in the population by exponential growth
divisions can be as fast as every few minutes

Question 24

fragmentation

Answer 24

in filamentous forms
separation disk or necridia (controlled cell death)
hormogonia —> portions of filament that are separating (still together within sheath)
2 separate filaments

Question 25

endospores

Answer 25

internal
form within the parental cell wall and are released when the wall ruptures
subdivision
cells that function in as vegetative agents of dispersal

Question 26

exospores

Answer 26

external
are budded off from the apical portion of the parental cell and are released
cells that function in as vegetative agents of dispersal

Question 27

taxonomy of cyanophytes

Answer 27

many groups not monophyletic
6 groups not orders
1. unicellular and colonial forms lacking specialized cells
2. filamentous groups lacking specialized cells
3. exospore producing groups
4. endospore producing groups
5. heterocyte and akinete producing groups
6. true-branching groups

Question 28

unicellular and colonial forms lacking specialized cells

Answer 28

unicells or aggregates of cells
all cells appear virtually identical internally
ex: microcystis or merismopedia

Question 29

filamentous forms without specialized cells

Answer 29

constrained cells into chains
formed arrays of trichomes in sheaths (no sheath evident)
false branching can result
ex: spirulina, lyngbya

Question 30

filamentous forms with specialized cells

Answer 30

heterocysts and/or akinetes present
ex: anabaena

Question 31

spore producing groups

Answer 31

attachment to the substrate
spores are released from upper end of cell or internally
ex: baeocyte

Question 32

true branching multicellular forms

Answer 32

change in plane of cell division
perpendicular growth
formed arrays of cells that divide in 2 directions

Question 33

prochloroccus

Answer 33

most abundant photosynthetic organism on the planet
smallest photosynthetic organism
simple coccoid unicells
unique form of photosynthesis with chlorophyll a and b
accounts for an estimated 13-48% of global oxygen production
~50% of marine carbon fixation
important carbon source and sink

Question 34

trichodesmium

Answer 34

“sea sawdust” large colonies
important nitrogen fixers in the ocean (50%)
no heterocysts
fixes nitrogen with photosynthetic reactions and specialized pathways
form massive blooms in tropics and subtropical oceans
not associated with eutrophication
grow as filamentous colonies
primary production and carbon sequestration

Question 35

stromatolites

Answer 35

diverse fossils of cyanobacteria, over 2 billion years old
some of the first forms of life are recorded in
layers of microorganism biofilm with carbonate grains embedded
diversity of structural types

Question 36

azolla and anabaena

Answer 36

important for commercial uses
symbiosis of cyanobacteria and water fern
utilizing mutualistic relationship
fixes large amounts of nitrogen
used for cultivation of rice
liberates nitrogen into water
rice more productive
anabaena in space?