Symbiogenesis

A couple of weeks ago, I was in a room with privileged people - students, professors and researchers, listening to a talk which dealt with  the topic on Symbiogenesis. The speaker, Dr. Lynn Margulis,  was a not an ordinary person as she has been credited for the widely-accepted  endosymbiotic theory of the origin of eukaryotic cells. She is currently a distinguised professor in the department of geosciences at the University of Massachusets in Amherst.

It was about 6 years ago since I knew about Dr. Lynn Margulis. I was a member of a large delegation of biology professors from all over the US grading the 2006 Advanced Placement test in Biology (APBiology) in the University of Nebraska -Lincoln. No, she was not one of us. But her name always popped up in almost every page of the test booklets I read. The question was about the origin of the first eukaryotes and many students unnecessarily mentioned her as the proponent of the theory.

In that lecture, I paid particular attention on how she talked and how she relayed the wealth of information within a limited period of time in a presentation. For people like her, I thought,  are exceptional mortals and are endowed with the unique critical skill in weaving a major  scientific concept which makes it to the college textbook. And all I wanted was to emulate her wits and style.

Symbiogenesis, the merging of two entirely different organisms to form a new organism, is not really new. This idea was synthesized in the 1920s by a famous Russian botanist in a book titled Symbiogenesis: A New Principle of Evolution. Symbiogenesis was considered a major driving force in evolutionary biology along with Darwinian's natural selection. This treatise on symbiogenesis however, suffered the same fate as Gregor Mendel's theory of inheritance,  gathering dust in the library's bookselves over a long period of time as they were ignored by the scientific community. In just about a year ago, The Harvard University Press published a English Translation of the book where Lynn Margulis was one of the co-editors. The re-discovery of symbiogenesis has begun an exciting era in evolutionary research.

We share this planet with a gazillion of other living organisms. We share our bodies to tons and tons of other living organisms. Lice in our heads or pubes; worms inside our guts; fungi in between our toes, armpits and yeasts in the vagina; and of course the truckloads of bacteria and protozoans which call our intestines their abode, others invading every inch of our skin, eyes, nose, mouth and not to mention the genitalia. These are part of who we are. They make vitamins for us! They make us stinky! Many of the them form our normal biota where they offer themselves the 'military' protecting our bodies from invading 'alien' microorganisms.   

Similarly, in bodies of other organisms live tons and tons of living hitch-hikers.Symbiosis, the close association and coexistence of different forms of organisms, therefore has become the way of life. Symbiosis causes different consequences to the parties involved, parasites get 'fat', hosts nutrient-deprived, commensals mutually benefited. When the host becomes immunocompromised, the opportunistic pathogenic endosymbionts (those who live within our bodies)  are out there to defeat the host in a disease. In short, both the endo- and ecto-symbionts make our either bodies better or bitter.

Dr. Margulis used the sea slug, a close relative of the squids and octopuses, as one example that seems to exemplify the process of symbiogenesis. Many different species of sea slugs obtain defense structures, like the nematocysts from the deadly jellyfish, portuguese-man-of-war. Instead of being destroyed, these stinging cells are kept by the slugs for their own defense. There is a certain species of sea slugs which feeds voraciously on algae. Instead of being broken down as food, some algae stayed infact and remained functional within the animal body, as endosymbionts. The slug, which is shaped life a flat leaf, looks green because of the presence of the algae which carry on photosynthesis inside the slug body. So here is an animal that, through its of endosymbionts, is capable of photosynthesis. Examination of the eggs produced by the slug showed the presence of chloroplast genes in the cytoplasm. 

This could just be the tip of the iceberg. There could be many animals out there whose close contact and  strong association with other organisms, may result to the formation of an entirely different organism in the long run. In here, missing links will not be an issue. The scientist may just have to look closely which other organisms that are associated. And by looking at the different DNA fingerprints, the identity of these associated oganisms can be obtained  by blasting their DNA sequence with the extensive database that are available.

Here is a nature's way of making transgenic animals!