IV. Bluegreen Bacteria:
Kingdom Eubacteria, Phylum Cyanobacteria
It might surprise many readers that marine bacteria constitute important components of
the marine ecosystem. However, with its primary focus on animal life, the Alaska
SeaLife Center does not exhibit these organisms. Nonetheless, we present a very basic
overview of the Kingdom Eubacteria in this chapter and also describe two species of
Eubacteria that are very important to the marine environment.
Characteristics of the Eubacteria (including the Cyanobacteria)
• Single celled, filamentous, or colonial (groups of cells living together) organisms that
are typically microscopic.
• cells generally 1 to 10 μm (i.e., 10-6 meters) in size (about ten times smaller than
plant, fungus, or animal cells), but some filamentous genera may reach 20 or 30 µm
in diameter.
• cells lack a membrane-bound nucleus, but instead have their DNA diffusely arranged
in the cell as a single, loop-shaped molecule
• reproduction occurs by cell division and fragmentation.
• most all have a cell wall outside their membrane.
• cell shape can be spherical, rod-like, curved, spiral or filamentous.
• originally based on cell shape and physiology, the classification of all Eubacteria is
currently being revised using molecular (DNA) characteristics.
• many marine Eubacteria utilize sources of dissolved organic carbon as an energy
source and do not undergo photosynthesis.
• one group of Eubacteria, the Cyanobacteria, does photosynthesize (i.e., utilize light
energy to produce carbohydrate from carbon dioxide); this photosynthesis releases
oxygen into the atmosphere in return for carbon dioxide.
• Cyanobacteria, also called blue green algae, are known to be some of the first living
organisms on Earth and are thought to be the source of all early oxygen in our
atmosphere.
• Cyanobacteria occur in planktonic and benthic habitats, in fresh and marine water, as
symbionts on plants, fungi, or invertebrates, and even in hot springs
• many Cyanobacteria undergo nitrogen fixation, incorporating elemental nitrogen
into biomolecules that are essential for the survival of most all eukaryotic algae and
plants.
• In marine habitats, Cyanobacteria are particularly important on mudflats, in estuaries
and in the open ocean.
Although the Alaska Sea Life Center does not exhibit these microscopic organisms on
purpose, many Eubacteria are present on and in the plants and animals on display and in
the seawater system. But, only a few of these are Cyanobacteria. We present two
important Cyanobacterial species here that can affect marine ecosystems in dramatic
ways.
1.
Black Felt/Black Balls/Tar Spot, Calothrix crustacea
Kingdom Eubacteria
Phylum Cyanobacteria
http://www-biol.paisley.ac.uk/biore/Eubacteria/Calothrix.html
Class Cyanophyceae
Order Nostocales
Family Nostocaceae
Genus and Species Calothrix crustacea
Occurrence………………………
•
•
•
•
Form/Function…………………..
•
•
•
•
Cosmopolitan
Occuring in benthic marine and estuarine
habitats from the high intertidal down to the
subtidal.
Often very abundant, sometimes felting the
substratum or forming a slippery dark band
high in the intertidal similar to that of the
black lichen, Verrucaria maura.
Attaches to rock, seagrasses, marsh grasses,
mangrove roots, seaweeds, and invertebrates.
Thalli consist of sheathed tapering trichomes
(filaments) that narrow to a hair; trichomes
are unbranched or falsely branched and bear
basal and rarely intercalary heterocysts.
Trichomes range from 8-18 µm in basal
diameter and may reach 1 mm or more in
height.
Trichomes may be solitary, in small groups,
or radially arranged from a central core into
hemispherical or globose ball-like clusters,
referred to by some as the separate genus
Rivularia.
Gelatinous sheaths enclose from 1-3
•
•
Reproduction …............................
•
Noteworthy Facts …......................
•
•
•
•
trichomes and help to prevent them from
drying out.
In the Rivularia form, the radiating trichomes
are also enclosed in a somewhat firm
mucilage that may be layered and encrusted
with lime. These colonies are generally 2-3
mm in diameter, but they are known to reach
6 cm in some habitats.
The colonies of Calothrix appear black, dark
olive, or bluegreen, but the color of individual
trichomes is typically yellow-green.
Asexually by hormogonia, short propagating
filaments that form when intercalary cells die
and cause the trichome to fragment.
Heterocysts are the site of nitrogen fixation in
this species
Known as “tar spot” in the tropics due to the
black dots that it makes on floating
Sargassum, Calothrix plays a major role in
the survival of this species in the nutrientpoor tropical seas.
Some forms of Calothrix can bore into
limestone.
In Alaskan estuaries, Calothrix occurs
abundantly on red algae late in the summers.
2.
Sea Sawdust, Trichodesmium erythraeum
Kingdom Eubacteria
Phylum Cyanobacteria
Class Cyanophyceae
Order Oscilliatoriales
Family Oscilliatoriaceae
Genus and Species Trichodesmium erythraeum
Occurrence………………………..
•
•
Form/Function ……..……………..
•
•
•
Reproduction…................................
Noteworthy Facts…..........................
•
•
•
Marine and planktonic
important in warm temperate and tropical
seas.
Microscopic narrow filaments (trichomes)
that group together into flake-like or scalelike bundles (visible to the naked eye) that
are held together by a soft transparent
sheath material
Trichomes are 7-25 µm in diameter and
sometimes narrow at their ends; the
trichome tips may be hemishpherical or
truncated.
Cells have gas vacuoles that help with
flotation.
Hormagonia aid in asexual propagation
Forms massive surface phytoplanktonic
blooms that discolor the water; sometimes
these blooms are so large and conspicuous
that they can be photographed from outer
space
Because Trichodesmium species can fix
nitrogen (i.e., they can incorporate
atmospheric nitrogen into molecules which
can be absorbed and used by plants), their
•
•
•
blooms can have a large impact on nutrient
cycling in marine ecosystems
Such blooms can impact changes in
phytoplankton and zooplankton structure
First Trichodesmium bloom described was
that of Captain Cook sailing in Australian
waters in the 1700s; the yellowish bloom
was thought at first to be a sandbar on
which the ship might run aground.
Word origin for genus name is Greek:
trichos = hair desmus = joined