Cyanobacteria + general algae Flashcards
Sheath in Cyanobacterial cells. Thin electrondense layer, surrounding cells or groups of cells in a more or less adherent way. It can be observed both under the light and the electron microscope.
It is more frequent in the filamentous forms
Capsule generally consists of a thicker and more compact layer of the sheath, tightly associated with the cell surface.
It is more frequent in the coccoid forms.
(Cyanobacterial cell)
Slime is the polysaccharidic material that is found dispersed around the cyanobacterial cells, rapidly secreted externally.
Cyanobacterial cell is generally occupied for the most part by thylakoidal membranes (or thylakoids), whose spatial organization in the cytoplasm seems to have a taxonomic value.
Other cellular inclusions of cyanobacteria are carboxysomes; micro-compartments containing the enzymes carbonic anhydrase and Rubisco, where the carbon dioxide fixation occurs
In cyanobacteria: Formation of specialized , spore-like cells, much larger than the vegetative ones with thickened walls, called akinetes. Can accumulate and store various essential material, that allow the survival of cyanobacteria for many years when environmental conditions are not favorable for growth (drought, cold, lack of nutrients).
Planktonic cyanobacteria is able to perform vertical migration by buoyancy. This occurs by modulating the production of gas vesicles, favouring buoyancy or by the production of starch of the Cyanophyceae granules and cyanophycin, acting instead as ballast.
Pili in cyanobacteria.
Many coccoid forms achieve gliding motility through particular structures called pili
Many cyanobacterial species are a component of the marine phytoplankton, where in the presence of eutrophic waters, they are able to produce considerable biomass, causing real blooms, with the colouring of the water in green, brown or red.
Microbial mats are dense benthic communities of cyanobacteria, in which the different species are distributed vertically to form distinct layers, often recognizable to the naked eye due to the different colours, due to the pigments of the organisms that compose them.
Stromatolites are found all over the world and are thought to have been produced by “light loving” microorganisms.
In the Precambrian, stromatolites grew in a wide variety of habitats, from shallow coastal areas to deep water, where they gave rise to domes or branched columns.
The number of stromatolites dates back to a maximum of 700-800 million years, then suddenly declined.
Research suggest that this decrease is due to the evolution of numerous types of herbivorous gastropods, which fed on these covers
Cyanobacteria: Spirulina sp. (Oscillatoriales)
Cyanobacteria: Oscillatoria princeps (Oscillatoriales)
Cyanobacteria: Chroococcus sp. (Chroococcales
Cyanobacteria: Hapalosiphon hibernicus (Stigonematales)
Cyanobacteria: Nostoc sp. (Nostocales)
Genus Prochloron of Cyanobacteria
The genus Prochloron includes coccoid forms, living as symbionts in colonial ascidians of tropical and subtropical seas.
Cyanobacteria: Synechococcus.
This genus is represented by cylindrical unicellular organisms important as a primary producers of marine and freshwater plankton.
Also present on the surfaces of algae and plants.
The cells do not have a mucilaginous layer.
Both marine and freshwater forms belonging to this genus have been associated with whitening of the waters, following the production of fine carbonate granules.
Cyanobacteria: Gloeocapsa.
This genus is represented by colonies consisting of multiple cells.
It is found both in seas, lakes, soils or other terrestrial surfaces.
Species belonging to this genus can form black bands
in coastal intertidal rocks.
Each cell has a distinct mucilaginous sheath, surrounded by older mucilaginous material.
Cyanobacteria: Trichodesmium
Cyanobacteria: Oscillatoria filaments
Cyanobacteria: Microcoleus
Cyanobacteria: Spirulina
Rhodophyta: Phycobilisomes
On the thylakoid membranes there are phycobilisomes, formed by the aggregation of phycobiliproteins, they constitute the extrinsic antenna of photosystem II.
Algae:
UNICELLULAR FLAGELLATE VEGETATIVE CELLS – MONADOID level
Most primitive type in most algal groups. The other types originated from this one
Flagella may vary in number and arrangement
Algae: COLONIAL FLAGELLATE CELLS
They can vary in number, arrangement and the way they are joined together
generally the colony has the shape of a flat disc or sphere
the cells can be in direct contact or joined by a mucilaginous sheath
Algae: PALMELLOID AGGREGATIONS
(tetrasporal level)
Cells are well separated but enclosed within a common mucilaginous envelope
Algae: COCCOID CELLS AND NON-FLAGELLATE COLONIES (Pediastrum sp.)
Single or aggregated cells in regular shaped colonies: COENOBIUM
Sometimes there is mucilage around the colonies
Algae: Microdictyon sp.
The coenobium of Microdictyon sp. consists of many cylindrical cells which are joined end to end to form hexagons or pentagons.
The colony appears to be a network
Ulotrix sp.: Uniseriate filaments
Algae: COCCOID CELLS AND NON-FLAGELLATE COLONIES (Scenedesmus sp.)
Single or aggregated cells in regular shaped colonies: COENOBIUM
Sometimes there is mucilage around the colonies
Rhodophyta: Multiseriate filaments
Asparagopsis sp. : branched filaments
Oedogonium sp. : unbranched filaments
Pseudoparenchymatic thallus in Halymenia floresia
Parenchymatous thalli in Ulva lactuca
SIPHONOUS THALLUS in Caulerpa mexicana (unicellular multinucleate organism)
SIPHONOCLADOUS THALLUS
in Cladophora glomerata (Multicellular multinucleate alga)
MIXOTROPHY in phytoplanktonic species
Species with special feeding tube –> peduncle
