CH.(6)

By: Raghdah A. Malibari

2012 - 2013

Cyanobacteria

Heterocyte and akinete – producing cyanobacteria

Nostoc

Nostoc is frequently abundant in flooded rice paddies where it contributes to the fertilization of some 2 million hectares.

Primarily occurs in terrestrial habitat.Association with fungi in lichens and with some bryophytes and vascular plants.Moist rocks and cliffs. Alkaline soil.In wet meadows.At the edges of shallow lakes.

Bent or naked filaments of round cells are held in a firm mucilaginous matrix to form colonies.The sheaths colored by yellow, brown or black.Transiently motile hermogonia are produced these typically have heterocytes at the ends.

Characteristics

Habitat

Cellular structure Nostoc sp. Colony of trichomes

Nostoc sp.Colonies ("balls")

Anabena

Primarily planktonic in fresh waters and marine waters such as the Baltic Sea some forms can be nuisance bloom formers and toxin producers.

Consist of filaments of spherical cells resembling in a mucilaginous matrix .Molecular phylogenetic analyses indicate that Anabaena is not monophyletic group separated into multiple classes.

Habitat

Cellular structure

Illustrates polar plugs of heterocyst

Anabena sp.

Aphanizomenon

Aphanizomenon that which makes itself invisible.Large blooms may form in the Baltic Sea and in eutrophic inland waters.

Occurs in the Baltic Sea and in eutrophic inland water.

Consist of distinctive aggregations of filaments (so large as to be visible).Molecular phylogenetic within Anabaena as the Aphanizomenon. May not be monophyletic.

Habitat

Cellular structure

Characteristics

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Aphanizomenon flos-aquae

Cylindrospermum

Occurs in freshwaters including soft, acid lakes.Forming dark green patches on submerged vegetation and on moist soil.

Filaments of vegetative cells ( square or rectangular cells). Heterocyte at one end are enclosed in loose mucilage. A large ,highly or nemented akinete may develop from the lowermost vegetative cell.

Habitat

Cellular structure Cylindrospermum sp.

Cylindrospermum sp.Clusters of trichomes

Important nitrogen – fixing.C.Raciborskii this species produces the hepatotoxin cylindrospermopsin caused poisoning.

Plaktonic bloom-former in eutrophic temperate. Tropical freshwater around the world.

Rectangular cells occur in linear or coiled filments having a basal heterocyte.Akinetes may form basally. If akinetes are not present , correct species identification may be difficult.

Cylindrospermopsis

Habitat

Cellular structure

Characteristics

C.raciborskii

C.raciborskii

Tolypothrix

The frequency of false branching gives these algae a woolly appearance.

Plaktonic.Entangled among submergent vegetation in freshwater lakes (soft or acidic water ).

Filaments are enclosed in a sheath of variable consistency . Highly false branched usually at a heterocyte ( single false and sometimes double false branches occur).

Habitat

Cellular structure

Characteristics Tolypothrix filaments form wooly mats.

Tolypothrix sp.

Scytonema

It is a phycobiont in several orders of lichen.

Forms dark tufted mats in masses of other algae. Vegetation in lakes. On terrestrial surfaces ( stones , wood and soil ).

Often double false branches occur , this result has been interrupted by death of a cell . Less commonly by heterocyte differentiation. Heterocyte wall may be darkly pigmented. Sheath is tough and sometimes clearly layered ( colored brown or orange ).

Habitat

Cellular structure

Characteristics

Scytonema sp. False branches

Scytonema homoni

Gloeotrichia

Gloeotrichia colonies often detach from substrate , becoming planktonic. Growths can reach bloom properations.

Occurs in freshwater habitat attached to submerged substrate.

Akinetes occur adjacent to basal heterocytes ( sometimes appearing in chains).

Habitat

Cellular structure

Characteristics

Gloeotrichia echinulata

Gloeotrichia sp.

True – branching cyanobacteria

The primary phycobiont in certain lichens and is associated with boreal mosses. Contributes to nitrogen availability.

Moist rocks. Soil.Some species are aquatic , attached to submerged wood or other algae. Form tufted mats or cushions on submerged portions of lake macrophytes.

The filaments are more than one cell in width as (multiseriate or pluriseriate). Are true-branched.

Stigonema

Habitat

Cellular structure

Characteristics

Stigonema mammilosa from Lake

Stigonema sp. from a river

Raghdah A. Malibari