The World's Largest Bacterium Is Visible To The Naked Eye
Thiomargarita namibiensis lives off the coast of Namibia in the sediment on the ocean floor. Its large size is due to its central vacuole, which is full of nitrates. Typical cells range between .1 and .3 millimeters in size, but the largest specimens reach diameters of .75 millimeters. Its genus name means "sulfur pearl," and indeed, the bacteria look like tiny, lustrous pearls due to sulfur granules within them.
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Key Facts In This Video
The naked human eye cannot distinguish objects smaller than .1 mm. (0:26)
At 75 nanometers across, the Mimivirus is one of the largest known viruses. (0:53)
A single carbon atom measures about .2 nanometers across. (1:25)