Cyanobacteria
Cyanobacteria are arguably the most successful group of microorganisms on
Earth. Formerly called blue-green algae, they belong to a group oxygenic
photosynthetic bacteria comprised of unicellular to multicellular bacteria
possessing chlorophyll a and carrying out oxygenic photosynthesis. Cyanobacteria
are the only known organisms capable of fixing both carbon dioxide (in the
presence of light) and nitrogen. Their photosynthesis was the basis of the
"oxygen revolution" that transformed Earth's atmosphere.
Cyanobacteria carry out the same type of photosynthesis that is
characteristic of eukaryotic cells. They contain elaborate and highly organized
internal membrane system called photosynthetic lamellae.
One of the distinguishing features of cyanobacteria is the presence of
particular photosynthetic pigments: the phycocianins (blue) and the
phycoerythrins (red), which do not occur in eukaryotic algae or higher plants.
These pigments absorb lights at shorter wavelengths than chlorophyll and thus
increase the ability of the cells to utilize solar radiation in the green-yellow
region. As a consequence, the cyanobacteria can grow at low light intensity and
in clear waters at considerable depths.1
Cyanobacteria may live free or form colonies. Depending on the species and
growth conditions, colonies may range from flat sheets one cell thick to
filaments to spherical balls of cells. Some filamentous colonies of
cyanobacteria differentiate into three cell types: vegetative cells, spores, and
heterocysts.
Some cyanobacteria species produce carcinogenic toxins. Most reports of acute
animal and human cyanobacteria-related poisoning arise from consumption of
contaminated drinking water.2
Cyanobacteria genera include:
- Anabaena
- Aphanizomenon
- Cyanothece
- Cylindrospermopsis
- Microcystis
- Nodularia
- Nostoc
- Oscillatoria
- Plectonema
- Spirulina
- Synechococcus
- Synechocystis
References:
1. Oceans and human health: risks and
remedies from the seas By Patrick J. Walsh
2. Life: The Science of Biology by David Sadava, H. Craig Heller, David M. Hillis
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