Mitochondrion Cell Organelle: A Symbiotic Cyanobacteria

An archaic ancestor (a prokaryotic Cyanobean symbiont) resides in our cell, a case of organisms within organisms, providing mutual benefit, the recipe for long-term evolutionary success.

In cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5 to 1.0 micrometer (μm) in diameter. Mitochondria are sometimes described as "cellular power plants" because they generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy. In addition to supplying cellular energy, mitochondria are involved in other tasks such as signaling, cellular differentiation, cell death, as well as the control of the cell cycle and cell growth. Mitochondria have been implicated in several human diseases, including mitochondrial disorders and cardiac dysfunction, and may play a role in the aging process. The word mitochondrion comes from the Greek μίτος mitos, thread, + χονδρίον chondrion, granule.

Although most of a cell's DNA is contained in the cell nucleus, the mitochondrion has its own independent genome. Further, its DNA shows substantial similarity to bacterial genomes.

Origin: Mitochondria have many features in common with prokaryotes. As a result, they are thought to be originally derived from endosymbiotic prokaryotes.

A mitochondrion contains DNA, which is organized as several copies of a single, circular chromosome. This mitochondrial chromosome contains genes for redox proteins such as those of the respiratory chain. The CoRR hypothesis proposes that this co-location is required for redox regulation. The mitochondrial genome codes for some RNAs of ribosomes, and the twenty-two tRNAs necessary for the translation of messenger RNAs into protein. The circular structure is also found in prokaryotes, and the similarity is extended by the fact that mitochondrial DNA is organized with a variant genetic code similar to that of Proteobacteria. This suggests that their ancestor, the so-called proto-mitochondrion, was a member of the Proteobacteria. In particular, the proto-mitochondrion was probably closely related to the rickettsia. However, the exact relationship of the ancestor of mitochondria to the alpha-proteobacteria and whether the mitochondrion was formed at the same time or after the nucleus, remains controversial.

A recent study by researchers of the University of Hawaiʻi at Mānoa and the Oregon State University indicates that the SAR11 clade of bacteria shares a relatively recent common ancestor with the mitochondria existing in most eukaryotic cells.

Humans must think like a Mitochondrion: Parasites that do not debilitate their host can get along indefinitely.  But the relationship that works the best is that of symbiont.  Bacteria have been at it for literally billions of years.  At some point prokaryotic cells found a comfortable shelter inside larger cells, and lent their particular expertise to their host’s success.  The mitochondrion within the cells have their own distinct DNA.  They do provide the abundant supply of energy that the cells enjoy.  Within animal cells, mitochondria are small powerhouses providing benefit to the cell.  They, too, show evidence of their colonial past in their distinct DNA.Organisms within organisms, providing mutual benefit, the recipe for long-term evolutionary success.  

If we are wise, we will mimic this strategy.  We will seek ways to become a contributor to the overall health of the greater organism.  Chloroplasts and mitochondria didn’t plan out their success; it wasn’t intelligently designed.  Countless millions of other viruses and bacteria were mutating, evolving, swapping genetic code .......and this worked.  It was perpetuated.

*Note: all pictures thankfully shared from various sources on Internet