Multigenre: Symbiosis- Some insight behind biological interactions

PROLOGUE

Dear readers,

Since I was a kid, I’ve always had a fascination for Science. You might say, “Science? It’s such an extensive field! Be more specific.” I’m very fond of everything Biology has to offer. The world and all that is in it is so heterogeneous and complex, and we tend to ignore a lot of what it offers.  My main interest lays in how all organisms interact and need others in order to survive; but I never truly understood the extent of these interactions until I took more advanced Biology courses, and this concept is known as symbiosis.

There are thousands of symbiotic relationships, some that we see yet don’t comprehend the mechanics and the complexity that is before our eyes, and others that we can’t see but happen on a daily basis, an example being in our own bodies. Knowing and understanding the importance and learning to appreciate the beauty and the greatness of what surrounds us is fundamental in order to truly appreciate them. My goal is for you to get a taste of this topic and comprehend that we, Homo sapiens, can’t survive on our own. We depend on many other organisms to be able to live. We need to be more conscious of our surroundings and be less selfish.

Throughout this project I will explain and show several symbiotic relationships amongst animals, humans, bacteria, fungi, and plants. In order to accomplish this, different genres will be used. In order for you to understand, an introduction with background information will follow this letter.

INTRODUCTION

Each and every organism depends on something (i.e. nutrients, temperature, acidity, oxygen levels, and atmospheric conditions) or someone (i.e. human, animal, bacteria, fungi) to be able to live. Sometimes this dependence can be more prominent in some cases than others. Symbiosis focuses on interactions between two or more organisms of different species; seen in a more simplistic way as “the living together of two unlike organisms”. According to Paracer (2000), “Organisms that are involved in a symbiosis may benefit from, be harmed by, or not be affected by the association.” These associations are known as mutualism, parasitism, and commensalism, respectively. There are also others ways of classifying a symbiosis.

Symbiosis can be classified according to where, on the host, the symbiont is encountered. If the symbiont is located within the host (e.g. intestine), it is known as an endosymbiont; however if it is located on the surface of the host (e.g. skin), then it is known as an ectosymbiont. A symbiosis can also be classified by the dependence of the relationship; some can be more demanding than others. When one of the parties involved can live with or without the other, the symbiosis is known as obligate, one the other hand, if the association isn’t necessary for either one of the individuals involved to live, then it is facultative. Sometimes these associations result in specimens that otherwise wouldn’t be found in nature.

One of the most common composites obtained from the association between two organisms is that of an algae (and/or cyanobacterium) with a fungus, which together form, lichens. The morphology, physiology, and biochemistry isolated from the lichen are completely different from those acquired from these organisms separately. This cooperation allows them to live in extreme environments. Another common symbiotic relationship is that of Homo sapiens, humans, with several bacteria, i.e. E. coli, which inhabits our intestines and produces vitamin K₂ for us.

On occasions the symbiont can provide the host with special abilities. An example of this is that of the squid Euprymna scolopes and the bacterium Vibrio fischeri. Investigations done by Nyholm (2004) presented the studies done on the relationship of both organisms. The squid has a light-organ which is home to a luminescent bacteria. V. fischeri is found in low concentrations. The squid digs a hole into the sand, where it hides out during the day, before that it expels 95% of the bacteria which it holds inside its light organ. The other 5% that stays inside multiples during the day, once the night arrives, they’re ready to work providing light to the squid, which keeps it away from predators. The light organ is specific to this bacteria. In this case, both organisms benefit from this interaction.

Symbiosis is a widespread and complex subject, not only does it focus on hundreds of associations between organisms of different species; but  it is also used to explain the origin of the eukaryotic cell, as well as being denoted a factor in the formation of new species; and most importantly, is provides diversity amongst living organisms.

THE ANNOTATED BIBLIOGRAPHY

Margulis, L. (1998). Symbiotic Planet: A new look at evolution. Amherst, Massachusetts: Basic Books.

Throughout the book Lynn Margulis, other than talking about how Science marked the different stages of her life; she shares her perspective on different aspects of the field, mainly symbiosis. Her main focus is her serial endosymbiotic theory (SET), which according to her explains the origin of the first eukaryotic cell. Some accept this theory, while others criticize it (she has rough words for those who do!). She also tries to convince us how some symbiotic relations end up forming new species, and even dedicates a chapter to GAIA, concept that says that every living organism is connected to the Earth by some invisible net.
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Douglas, A.E. (2008). Coral Bleaching- how and why? Marine Pollution Bulletin. 46, 385-392.

The article explains what coral bleaching is and the different factors involved. In my case, I always thought that coral bleaching was only associated with contamination and temperature change, but this is not the case. Bleaching refers to the loss of color in symbiosis between a dinoflagellate algae, Symbiodinium, and marine benthic animals, in this case, corals. Bleaching results in depressed growth and increased mortality of corals, which are one of the most diverse ecosystems on the planet. It also explains how corals sometimes expulse Symbiodinium. It is in question on whether this is done from time to time as a part of their life cycle, or if they do this to find another species of Symbiodinium that suits their needs better due to environmental changes.

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Hosokawa, T, et.al. (2006). Strict Host-Symbiont Coespeciation and Reductive Genome Evolution in Insect Gut Bacteria. PLoS Biology. 4, 1841-1851.

The focus of this scientific article is to emphasize how hosts and symbionts tend to coevolve and a species of symbiont us specific to a species of host. Attached to this article are several phylogenetic trees, which illustrate the coevolution and coespeciation of some insects with their gut bacteria. There is also a focus on the main characteristics that endosymbionts possess: reduced genome, repetitive AT sequences, elimination of some metabolic pathways, etc. Investigators have been able to determine that these characteristics are the same for all endosymbionts.

________________________________________________________________________Rumpho, M.E., Summer, E.J., Manhart, A.R. (2000). Solar-Power Sea Slugs: mollusc/algal chloroplast symbiosis. Plant Physiology. 23, 29-38.

Sea slugs eat green algae, but first they suck out the chloroplasts, which gives them their green color. Chloroplasts are organelles that conduct photosynthesis. Therefore, not only does it allow these slugs to be green, but it also gives them a boost of energy. It is in question if this is a symbiosis, because this is a relationship between the sea slug and the chloroplast, which is an organelle not an organism. The sea slug has to continuously suck out these cells because the effect “wears” off, because it can’t replicate them inside its’ body.

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Nyholm, S.V., McFall-Ngai, M.J. (2004). The Winnowing: Establishing the squid-vibrio symbiosis. Nature Reviews: Microbiology. 2, 632-642.

The symbiosis described between the squid and the vibrio (bacteria) is quite fascinating. The squid has an organ that is specifically used to hold photosynthetic gram negative bacteria. The light produced by the bacteria creates a shadow at night, which fools predators and keeps itself from being attacked. Not only does the squid benefit from this, but so does the bacteria. In the morning, the squid buries itself under the sand and expulses 90% of the bacteria it holds; this helps increase the population of the microorganism

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GENRES

Video with pictures and descriptions

Travel Poster

Letter

Sunday August 15, 2010

Lovely V. fischeri,

I write this letter anxiously waiting for the moment we’re able to glide under the moonlight through the profound ocean tides again. Ever since I was a young adult, you’ve been with me. It wasn’t by chance, but evolution united us. My ciliated light-organ is compatible to you only. As soon as it senses your peptidoglycan, mucus starts streaming, as tears of joy, in order to allow you easy access through the ducts so you can reach the light-organ. You’ve saved my life in many occasions. Your bioluminescence allows me to cast an obscured and big silhouette that allows me to fool my predators. You keep me safe and I am tremendously grateful for that.

I am glad that this relationship isn’t entirely one-sided. It causes me great pleasure to be able to help you increase your population before I go sleep during the day. I know how difficult it would be for your community to grow otherwise. I am sure the future generations of my kind will be as glad as I am to have you.

Yours truly,

Euprymna scolopes “Squid”

P.S.

I cherish the time we spend in the Hawaiian waters.

Poem

Leaf- cutter ants at work

Leaf cutter ants passing by,

Walking up the trees,

Staring at the blue sky.

They hurry to their nest,

Usually a hole in the ground,

Then begins the harvest,

Rapidly, with no sound.

The product: fungi for them to eat

Total delight for the queen,

The main course of the feast.

One thing that they didn’t know

Was that an intruder would come and stop the show

Another fungi would come along

Attack and destroy their garden

Because it’s deadly and strong

Immediately the ants counterattack

With the bacteria they have in their necks and back.

The nest is now safe.

The ants have won the battle.

But they are to stay alert,

In case the enemy invades

Yet again their sacred place.

Quiz

Select the option that best completes the premise or answers the following questions.

Epilogue

It was only this semester that I was able to take a course that focuses entirely on Symbiosis. The fascination I have for it is such that I decided to do this multigenre on the subject, hoping it would cause an interest in others as it did in me. My main objective was for the readers to learn something new about Biology. I hope that after reading this work, they’re able to at least define the term and give some examples.

In order to explain and give information on symbiosis and some of the many symbiotic interactions, I used a video with picture and descriptions, quiz, letter, travel poster, and a poem.  In my opinion, this subject is better explained when using visuals, which is why I decided to show several pictures with their descriptions. A quiz allows me to test the reader or for the reader to evaluate how much they have learned by reading this work.  I wanted to view one of these interactions from the side of one of the organisms, which is why I decided to write a letter to the symbiont, pretending I was the host. The poem allowed me to be a bit more creative and a tad more abstract and the travel poster gave me the opportunity to include another visual.

At the end of the day, the sole purpose of all the genres is for you, the reader, to learn something you. As long as you take away some knowledge from this, I have accomplished my mission.

References

Aanen, D., Eggleton, P., et. al. (2002). The evolution of fungus-growing termites and their mutualistic fungal symbionts. PNAS. 99:14887-14892.

Geurts, R., Federova, E. (2005). Nod factor signaling genes and their function in the early stages of Rhizobium infection. Plant Biology. 8:346-352.

Fraune, S., Bosch, T. (2007). Long-term maintenance of species specific bacterial microbiota in the basal metazoan Hydra. PNAS. 104: 13146-13151.

Mueller, U., Dash, D. (2008). Coevolution between attine ants and actinomycete bacteria: A reevaluation. Evolution. 62: 2894-2912.

Yildiz, F., Visick, K. (2009). Vibrio biofilms: so much the same yet so different. Trends in Microbiology. 17: 109-118