plantas algas marinas, Diapositivas de Biología

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Cyanophyceae

BLUE- GREEN ALGAE

Cyanobacteria: distribution and numbers

In blooms (vannblomst) = mass occurrence with surface

scum and often toxin producing species

Include ca. 200 genera and 2000 species

All kinds of environments i.e. “ubiquitous”, mostly

aquatic (rarely at pH< 4-5),terrestrial on rocks and soils,

deserts, polar regions, other extreme habitats as thermal

pools (ca. 70 °C),hypersaline waters etc.

In symbioses, ca 8 % of lichens with cyanobacteria

as fycobiont + some with cephalodes (N

2

-fixation)

Why treat cyanobacteria

together with the algae?

3. Algal (and plant) chloroplasts originated from primary

endosymbiosis between heterotrophic eukaryote and a free

living cyanobacterium

Cyanobacterium taken up

by phagotrophic eukaryote

and eventually transformed

into a chloroplast

cyanobacterium

chloroplast

nucleus

Cyanobacteria: general characteristics

As all Prokaryotes absence of organelles:

• Nucleus
• Chloroplasts

Mitochondria

• Golgi bodies (dictyosomes)
• Endoplasmatic reticulum (ER)

Cyanobacteria: general characteristics

phycobilins

phycoerythrin

phycocyanin

allophycocyanin

carotenoids

A variety, some are

specific, others as in

algae and plants

Pigments:

chlorophyll a

(three genera with chlorophyll a + b)

scytonemin - extra cellular, UV-shielding pigment

Gram positive- peptidoglycan layer;

stains with crystal violet.

Gram negative- peptidoglycan layer

sandwiched by lipopolysaccharide and

protein layers; does not stain with

crystal violet.

Cyanobacteria: systematic characters

Unicellular

single cells as colonies

Morphology

(Order Chroococcales)

attached

(cells polar)

free living

Cyanobacteria: systematic characters

False branching

Cyanobacteria: systematic characters

True branching

only in some representatives of the order

Stigonematales

Cyanobacteria: systematic characters

Vegetative reproduction:

by binary division and fragmentation

Chroococcus

Merismopedia

“separation discs”

(necridia)

Cyanobacteria: systematic characters

by hormogonia, only in some

filamentous forms

Oscillatoria

Vegetative reproduction:

hormogonium

Lyngbya

Cyanobacteria: systematic characters

Formation of spores, only in some

unicellular forms

exospores

endospores

(= baeocytes)

Dermocarpa

Chamaesiphon

Asexual reproduction:

Cyanobacteria: systematic characters

completely absent

Sexual reproduction by gametes :

Viral transduction may happen