From “Study of Insect Bacteria Reveals Genetic Secrets of Symbiosis”:
June 20, 2013 — Mealybugs only eat plant sap, but sap doesn’t contain all the essential amino acids the insects need to survive. Luckily, the bugs have a symbiotic relationship with two species of bacteria — one living inside the other in a situation unique to known biology — to manufacture the nutrients sap doesn’t provide.
University of Montana microbiologist John McCutcheon describes such mutually beneficial relationships used to solve life’s little problems as “almost hilariously complicated. But animal-bacterial relationships are extremely common in nature, and it’s my goal in life to help people understand that it’s normal.”
You’d think he was talking about a reality TV show about weirdness, but no …
The researchers discovered the already complex three-way symbiosis actually depends on genes from six different organisms — three more than the number of species that currently exist in the symbiosis.
Tremblaya princeps is the larger of the two bacteria species living within special organs inside mealybugs. Tremblaya houses the smaller bacterial species, Moranella endobia, within its cytoplasm. But what makes Tremblaya truly odd is the size of its genome, or genetic code. With only 120 genes, its genome is the smallest known and smaller than many scientists consider necessary for life. By comparison, common E. coli bacteria have about 4,200 genes and humans have about 21,000.
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Symbiosis may turn out to be a powerful engine of evolution, which creates an interesting conundrum: Where did the original information come from? Most of the simpler strings were complex already, and the combination must work.