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Heliobacterium Chlorum Cells
Caption:
This scanning electron micrograph shows Heliobacterium chlorum cells, slow-moving bacterium that have been isolated from the soil at Bloomington, Indiana. (The bar at the bottom of the image equals 5 micrometers.)
Important: Use of this image is restricted. Please see “Restrictions” (below) for complete information.
More about this Image
First discovered in Thai rice paddies, the microbe known as Heliobacillus mobilis belongs to a group of bacteria called Heliobacteria. These bacteria respond to light and contain a form of chlorophyll that is intermediate to that found in green plants and cyanobacteria-the first bacteria to release oxygen on earth. Some scientists believe that early forms of cyanobacteria used energy from sunlight to transform the earth's atmosphere into an oxygen-rich blanket suitable for animal life.
Structural similarities between the two bacteria suggest the possibility that the Heliobacterium chlorum microbe could be the direct descendant of the ancient bacterium that produced cyanobacteria.
Further evidence to support this possibility includes the comparison of molecules called ribosomal RNA that are found in Heliobacteria and other microbes. Ribosomal RNA, which plays a crucial role in making proteins, has evolved slowly over the years. The type found in Heliobacterium chlorum closely matches the ribosomal RNA found in some older bacteria that do not respond to light, yet the RNA are strikingly different from that residing in other, more common light-sensitive bacteria. The Heliobacterium chlorum related to both cyanobacteria and older more primitive microbes seems clearly marked as an evolutionary link.
(Preview Only)
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Credit: |
F.R. Turner, Indiana University, Bloomington |
Decade of Image: |
1990 - 1999 |
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Categories:
BIOLOGICAL / General
Formats Available:
JPEG Format - 927K - 1200 x 791 pixel image - 300 DPI
Restrictions:
Warning: This image can only be used for private, educational, and non-profit purposes. Permission to use in any commercial vehicle, or in any for-profit manner is strictly prohibited.
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