Distribution

Cyanobacteria are found in almost as diverse a variety of habitats as other true bacteria. They are common in temporary pools or ditches, particularly if the water is polluted. They are not found in acidic waters, but they are abundant in other fresh and marine waters around the globe, from the frozen lakes of Antarctica to warm tropical seas. In the open oceans, cyanobacteria are the principal photosynthetic organisms in plankton, the tiny cells of the cyanobacterium Synechococcus commonly occurring in concentrations of 10,000 cells per milliliter. Trichodesmium is a marine, filamentous, nitrogen-fixing cyanobacterium that forms extensive mucilage-producing colonies in some tropical waters. Other bacteria multiply in the mucilage and become food for protozoa.

Kingd om Bacteria, Kingdom Archaea, and Viruses unpigmented bacteria f Cfc

Staphylococcus

Spirillum

Spirillum

Streptococcus

Streptococcus

Sarcina

Streptobacillus

Streptobacillus

Bacillus cyanobacteria cyanobacteria

Microcystis

Arthrospira

Arthrospira

Anabaena

Anabaena

Eucapsis

Eucapsis

Albrightia

Albrightia

Bacillosiphon

Bacillosiphon

Figure 17.10 Similarity of form between various unpigmented bacteria and cyanobacteria, x2000. After M. J. Pelczar, Jr., and R. D. Reid. 1972. Microbiology. 3d ed. The McGraw-Hill Companies. All rights reserved.

A different species of cyanobacterium is found in each temperature range of the hot springs of Yellowstone National Park, where water temperatures approach 85 °C (185°F). There the bacteria precipitate chalky, insoluble carbonate deposits, which become a rocklike substance called travertine. The deposits accumulate at the rate of up to 2 to 4 millimeters per week, with other cyanobacteria often forming brilliantly colored streaks in the travertine.

Cyanobacteria are often the first photosynthetic organisms to appear on bare lava after a volcanic eruption, and they also thrive in the tiny fissures of desert rocks. Some are found in jungle soils or on the shells of turtles and snails, while others live symbiotically in various types of organisms, including amoebae and other protozoans, diatoms, certain sea anemones and their relatives, some fungi, and in the roots of tropical palmlike plants called cycads. They also flourish in tiny pools of water formed at the bases of the leaves of tropical grasses and other plants, and they are well-known components of "compound" organisms called lichens, which consist of a fungus and a photosynthetic partner.

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