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How large are mitochondria compared with bacteria?
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mitochondrion
Mitochondria (red) are found throughout the cytoplasm of almost all eukaryotic cells (cell nucleus is shown in blue; cytoskeleton is shown in yellow).
Mitochondria and bacteria are similar in size, which is consistent with the endosymbiotic theory that suggests mitochondria originated from free-living prokaryotic organisms that were engulfed by ancestral eukaryotic cells.12
- Mitochondria: These organelles typically range in size from 0.5 to 10 micrometers (m).3
- Bacteria: Most bacteria are also in the micrometer range. For example, an average-sized bacterium like Escherichia coli is approximately 2 m long and 0.5 m in diameter, while many other common bacteria, such as Staphylococcus aureus, are up to 1 m in diameter.4
While there is significant overlap in their dimensions, some specialized bacteria can be much larger than mitochondria, with certain "giant" species reaching hundreds of micrometers in length. Conversely, mitochondria are generally considered to be within the same size scale as typical, average-sized bacteria.43