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Ecologie, facteurs du milieu

Ecologie dans l'environnement
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Akinete A thick-walled, nonmotile, resting, reproductive spore derived from a vegetative cell in which food has been concentrated
Antibiotic A chemical agent or substance produced by an organism which inhibits the growth of another (or itself).   Production of antibiotics by Cyanobacteria has been demonstrated.
Apical At the anterior end (apex); apical growth is growth at the apex of a trichome. Growth of the trichome can be either intercalary or apical, depending on the genus. The shape of the apical cell is sometimes used as a taxonomic character for Cyanobacteria.
Autotrophic : Self-feeding, producing organic matter through photosynthesis. Cyanobacteria are primarily autotrophic but some of them can grow under heterotrophic conditions.
Auxotrophic Nutrition in which organic compounds such as vitamins or amino acids are required.
Axenic A population of individuals or one strain free from other strains; synonym = pure culture. Obtention of axenic culture of Cyanobacteria is frequently difficult and tedious. However such culture are absolutely necessary for conducting physiological experiments. In particular the demonstration of the ability of a strain to fix nitrogen has to be done imperatively with an axenic culture
Baeocyte A small cell formed internally by multiple fission in a parent cell. Baeocytes are restricted to forms of Subsection II.
Bentic In an aquatic habitat, attached to a substrate

A chromoprotein in which the prosthetic group is a pigment tightly bound by covalent linkages to its apoprotein.

Binary fission Division into two products. It is the most frequent mode of multiplication in Cyanobacteria cells

A profuse growth of microscopic or semi-microscopic algae which discolors water; may be of short duration. May also occurs on wet soil. A significant N input in a paddy field can be expected every time a bloom of N2 fixing Cyanobacteria develops.
A concentrated population of planktonic algae macroscopically apparent.


Cyanobacteria can develop two kinds of branching.
False branching is the result of the extrusion of the filament throughout the sheath which may produce either a Y false branching (1) as in Tolypothrix or a germinate false branching (2) as in Scytonema.
True branching is produced by the lateral division of cells in a main axis as in Fischerella (3). Division can take place at right angle by involving a single parent cell (T-branching) or involve two cells of the main filament (inverted V-branching)(4).

Budding The asymmetric binary fission of a parental ceIl, in which one daughter cell is smaIler than the other.
Calyptra Thickening of the cell wall at the apex of a filament, forming a membranous cap; applied to a lid-like covering. The presence or absence of calyptra is a taxonomic character at the species level.

Enlarged or swollen at the apex; with a head. It is a taxonomic character at the species level

Centroplasm A central area of the Cyanobacteria cell (central body) with less pigment than the peripheral. It contains the granules of nuclear material
Chloroplasm The peripheral plasm of Cyanobacteria cell, usually more densely pigmented than the central body
Compensation point The level of photosynthesis which just equals or balances respiration. Under a dense rice canopy light intensity may be insufficient and algal photosynthesis may decrease beyond the compensation point.
Cyanophages Virus , specific of Cyanobacteria
Endospore A spore formed by multiple internal divisions of the protoplasm of a vegetative cell. Endospore are not enclosed by a thick wall but only by a membrane. Endospore are formed by Cyanobacteria belonging to Chamaesiphonales.
Endotoxine Poisonous substances produced and retained within a cell, and released only after death of the cell (contrary: exotoxin). Cyanobacteria as Schizothrix calciola and Anabaena flos-aquae produce lipopolysaccharide endotoxins
Eukaryotic Having membrane-bounded nuclei. Contrary: Prokaryotic. Cyanobacteria are prokaryotic organisms as other algae are eukaryotic organisms.
Euryhaline Having a broad tolerance to varying salinity. Some Cyanobacteria can tolerate from 35 g/l to 350 g/l NaCl.
Eutrophic A high productive water, rich in nutrients. Cyanobacteria are an index index of the level of eutrophication in freshwater ecosystems.
Filament For Cyanobacteria, comprises the trichome (row of closely adjoined cells) and the sheath when there is one. cell Separation between cells does not include an intercalating sheath, although a linear sheath may be present.
Fragmentation Formation of new individuals from segments arising by the breakup of a parental filament. This mode of reproduction is the most frequent among Cyanobacteria.
Gas vacuoles An area in cells that refracts light, during observation under light microscopy, because of its gaseous nature, often appearing red; composed of numerous gas vesicles.
Geminate Arranged in pairs
Gliding movement Movement of organism without flagella or pseudopodia when in contact with a substrate. Gliding movement is characteristic of some Oscillatoriales and Nostocales.
Hairs or Pili Colorless, typically elongate, unicellular or multi-cellular structures. In Rivularia ? and Gloeotrichia the trichome taper and the terminal cells become depleted of cell content so that distinct hairs are produced.
Heterocyst a thick-walled, usually transluscent cell of heterocystous Cyanobacteria, known to be the site of nitrogen fixation. Heterocysts occurs either basally or intercalary. The criterion for differentiating intercalary heterocysts from terminal heterocysts is the number of polar nodules (or granules). A polar granules is a thickening in the heterocyst wall at the front of the attachment of the heterocyst to the adjacent cell.Intercalary heterocysts are characterized by the presence of two polar nodules, while terminal heterocysts have only one polar nodule.
Heterotrichous A thallus which is partly prostate and partly erect. Example: Fischerella
Heterotrophic Obtaining food from organic substances in the medium. Some Cyanobacteria are able to grow autotrophically.
Hormogonium A usually motile segment of a Cyanobacteria capable of growing into another filament or a short section of a Cyanobacteria filament
Hormospore = hormocyst: A spore-like body formed by a short section of a filament becoming invested by a thick membrane and acting as a dormant reproductive element. Synonym hormoscyst. Example Westiella lanosa.
Multiple fission The internai fission of a parental cell into severe smaller cells which do not enlarge to parental size until after release.
Multiseriate Thallus or filament composed of several series of cells, as a result of ceIls in trichome dividing in more than one plane Example: Stigonema


A dead cell: a cell in the trichome of the Oscillatoriales which dries, becomes filled with mucilage, and so forms a weak link, providing for fragmentation.
Nitrogen fixation Incorporation of atmospheric nitrogen as a nitrogen source into the cells of certain Cyanobacteria and bacteria, by the reduction of dinitrogen to ammonia.
Oligotrophic Water with few electrolytes and with other features which render it low in productivity of biota-oligotrophic waters have less than 100 ppm of solution.
Periphyton Association of organism attached to and/or growing over submerged plants.
Phototactic Moving in reaction to light or various intensities of light.
Phototropic Moving in the direction of light source.
Phycobilin Biliprotein pigments of Cyanobacteria and red algae.
Phycobilisome The cellular organelle on the surface of thylakoids in which the biliprotein pigments are present in Cyanobacteria and red algae.
Phycocyanin Blue biliprotein pigment of Cyanobacteria and red algae.
Phycoerythrin Red biliprotein pigment of Cyanobacteria and red algae.
Plankton The community of small organisms suspended in water.
Prokaryotes Lacking membrane-bounded DNA (and Golgi apparatus, mitrochondria, and plastids). Cyanobacteria are prokaryotic microorganisms.
Propagule A multicellular structure functioning for asexual reproduction.
Pseudofilament A chain of cells in which ceIls are separated from each other by sheath material or a fibrous layer.
Pseudo-vacuole A gas-filled packed in cells of many Cyanobacteria, usually light refractive.
Saxicole Growing on rocks or rocky substrata.
Septa Cross partition or walls usually complete, sometimes interpreted.
Sheath An (often pectinaceous) investment outside the wall of certain cyanobacteria and algal cells
Spore A cellular agent of asexual reproduction (in Cyanobacteria synonym: akinete)
Stromatolite A fossilized, calcareous aggregate of Cyanobacteria
Symbiotism Two or more organisms living together or in close association, with various degrees of interdependence or parasitism.
Taxon A recognized, systematic entity of whatever ranks.
Thallus A plantlike body not differentiated into vascularized roots, stem, and leaves.
Thylakoid The intracellular membrane system that includes the reaction center, chlorophyll a (and b in some), and some carotenoid pigments.
Trichome A hair of gelatinous bristle, or an extension of the cell wall; name applied to the thread of cells in filamentous Cyanobacteria, minus the sheath.
Tychoplankton Floating or free-living organisms in shallow water of a lake, intermingled with attached vegetation and periphyton, usually near shore.
Umbrophilic Shade loving, referring to subdued light.
Unialgal A culture containing only one strain or species of alga - does not implies that it is a pure culture.
Uniseriate A filament in which there is a single series of cells, as opposed to a filament with more than one series.
Vegetative cell The normal cell that grows and divides by binar or multiple fission.
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Copyright P. A. Roger 2006