Liaisons of life Book

_Liaisons of Life_ by Tom Wakeford is a well-researched and very readable book on the importance of symbiosis in ecology and in evolution. Actually, to be more specific, it is a book about the importance of organisms' symbiosis with microbes (whether microbes with microbes or microbes with macroscopic organisms). The central tenets of this wonderful work are first that microbes (be they bacteria, protozoa, or fungi) are one of the most important innovative factors in evolution and are key parts of any ecology; Wakeford believed that the importance of the gene has been overemphasized. Secondly, interdependence among organisms is at least as important (if not more important) than competition between them; most organisms survive only by the "constant management" of their relationships with the microbes in and around them. Far from constant competition, it is often difficult to tell where one organism ends and another begins. Thirdly, this is a dynamic relationship; relationships can change, partners in symbiosis come and go, and the mutalist of today can become the parasite of tomorrow.

The acceptance of the importance of symbiosis and the beneficial role of microbes has been a long time coming. In the nineteenth century microbes first came to the attention of scientists thanks to the efforts of Louis Pasteur. It was he coined the word "germ" and single-handedly brought about the "antibacterial age," a time that lasted for several decades in which scientists saw microbes as things only to be eradicated. Additionally, views about symbiosis became tied up with the politics of the 1920s and 1930s, with bacteria and symbiotic relationships regrettably and very unscientifically becoming tied up with fears about Communism. It did not help that many pioneers in the field hailed from Germany and Russia.

Those who pointed out evidence of symbiosis often were met with derision and ignorant prejudice. Beatrix Potter was hounded out of biology in the 1890s for her views that lichens were made up of the alliance of two organisms; when the London scientific community treated her with disdain if not hatred she became instead a noted children's author and illustrator. Earlier in 1869 the Swiss botanist Simon Schwendener offered his "dual hypothesis" for the taxonomy of lichen, noting that they were both a fungus and an alga; his theories and works were treated with contempt and for a time calling someone a "Schwendenerist" was a term of abuse, meaning someone who waffled between two competing explanations for something. The idea that symbiotic organisms could be passed from one generation to another was for a time discredited thanks to associations with pre-Darwinian French evolutionist Jean-Baptiste Lamarck.

Wakeford provided numerous fascinating examples of symbiosis in nature. Many species of orchids for instance are so dependent upon fungal symbionts in their roots that they cannot survive without them. In fact mycorrhizal fungi - underground fungi that exist in a symbiotic relationship with the roots of plants - are essential in allowing many plants to get enough of many nutrients (notably phosphate). So essential are they that 90% of the plants on Earth have domesticated their own species of fungus. Mycorrhizal fungi can form vast underground networks, often linking more than one plant together. One researcher by the name of David Perry has said that the sharing of fungal symbionts between trees is so important they form a superorganism, what he termed a "guild." These fungal symbionts are known to allow one tree - perhaps suffering by being overly shaded - to draw upon the nutrients of another tree, thereby constituting a "mycorrhizal welfare state."

In addition to colonizing roots symbionts can colonize other parts of the plant; tall fescue grass, a dominant grass in the United States, has a species of fungus (_Acremonium_) that grows in the spaces between the grass's cells. This symbiont offers resistance to drought, increases seed production, and produces toxic alkaloid compounds that put off plant-eaters. So intimate is the relationship that grass seeds are infected while still in the seed coat.

Other examples of symbiosis in nature include the relationships of deep sea organisms with bioluminescent symbiotic bacteria, chemosynthetic symbiotic sulfide bacteria living in _Riftia_ tube worms around hydrothermal vents, the bacteria that allow shipworms and termites to digest wood (or in the case of anobiid beetles, it is a yeast-like fungus that allows them to eat wood), and the bacteria and protozoa ecosystem that exists in the four-chambered stomachs of ruminants such as cattle, sheep, and deer that allow these animals to digest grass. The most important examples of symbiosis though are undoubtedly the acquisition in eukaryotic cells of chloroplasts and mitochondria, a momentous evolutionary event, an example of an extremely intimate and permanent form of intracellular symbiosis which Wakeford skillfully explained.

Many species very actively manage their microbial associates. Corals bleach themselves - bleaching being the loss of the coral's symbionts, called _Symbiodinium_ - as a natural strategy to deal with changing environmental conditions. They do this to alter the makeup of their symbionts, to allow themselves to be repopulated by a new type of associate, one that perhaps is better suited for a changed environment. Researchers have discovered that leaf-cutter ants are continually domesticating new varieties of fungi by taking them into their nests; 862 types of nest fungi have been discovered, with evidence that ants periodically swap crop varieties with their neighbors.

As noted, the continuum between beneficial symbiont and parasite is a rather fuzzy continuum. Orchids for instance produce natural fungicides to keep their root symbionts from colonizing their stems; these and other plants can be overrun by their symbionts if they become weakened or malnourished. David Philip, the famous "bubble boy," had to live in a sterile environment because his body had no ability to cohabit with the numerous microbial associates in the human body (symbiotic bacteria make up a tenth of our body's weight and totaling 90 trillion cells outnumber our own body cells nine to one). If the intestines of any human are damaged formerly beneficial symbiotic microbes can create a life-threatening infection called sepsis.