Jennifer Holme
Termite and Lichen Lab Write-Up
Professor Zook
September 20, 2005
Discovering the Termite Gut
Background: It only seems natural to dislike termites because of their bad reputation for
causing millions of dollars worth of damage to homes and vegetation, but from a
biological standpoint, these creatures’ symbiotic relationship with their internal
microorganism is note-worthy.1 Since termites lack the enzyme required to digest
cellulose, the main component of wood, they enlist cellulase-carrying bacteria to perform
the task for them. In return, the termite provides food for the bacteria and refuge from the
outside environment. The relationship then becomes mutually beneficial for the termite
and its symbiont. 2 “By studying how a single termite survives, microbiologists have
begun to gain an entirely new understanding of symbiosis.”3
Purpose: To discover the microbial symbiotic relationship between the damp woods
termite (Zootermopsis augusticollis) and their hindgut bacteria.
Question: Is there a mutualistic relationship between the termite and its internal bacteria?
Experiment:
a. Materials: Microscope, Damp woods termites, tweezers, droppers, slides, and
saline solution.
b. Procedure: 1) Take tweezers and squeeze the hind end of the termite onto a
slide; releasing its internal fluid.
2) Drop a drop of saline on the slide, cover, and observe under a
microscope at multiple magnitudes.
Results:
Trichonympha
Trichonympha
1
http://www.biology.iastate.edu/intop/1Australia/Australia%20papers/EcolAusTermites%20.htm
http://www.biology.iastate.edu/intop/1Australia/Australia%20papers/EcolAusTermites%20.htm
3
http://occawlonline.pearsoned.com/bookbind/pubbooks/tfc/medialib/Applications/termites.html
2
There were multiple floating bacteria pushing each other around trying to move closer to
the food. Their undulipodia helped them move to the wood particles in the gut or pauch
of the termite.
Trichonympha (trick-owe-nymph-a) is one of the hypermastigid flagellates - flagellates with large
numbers of flagella. They and the trichomonads made up the group called the parabasalids almost all of which are endobiotic or parasitic. There is an anterior symmetrical rostrum, and the
numerous flagella arise from this region and from the region of the body immediately behind.
There are also spirochaetes attached to the back of the body. The nucleus is a large structure
lying some distance behind this. Cytoskeletal fibres with associated dictyosomes form bands
running from the points of flagellar insertion through the anterior part of the body. Food vacuoles
with particles of wood are found in the posterior part of the body. From the termite
Reticulotermes.
Trichonympha
This is an optical section across the top of the rostrum and the adjacent part of the cell showing
the cytoskeletal ribbons with which are associated the dictyosomes.
Spirochaetes are motile bacteria. They have very fine flagella attached to the cell surface, and
the rotating action of these propel spirochaetes through the medium. Spirochaetes have a spiral
body and twist through the medium. Several different sized-spirochaetes can be seen in this
image. From the termite Incisitermes. Very common inhabitants of the gut
http://microscope.mbl.edu/scripts/microscope.php?func=imgDetail&imageID=871
http://user.uni-frankfurt.de/~schauder/termites/termites.html
Protozoa from the hindgut of a termite
Lower termites can be described as a set of 6 families sharing the presence of symbiotic
intestinal flagellates. Higher termites are further evolved than lower termites in that they
have lost the flagellate protozoa and replaced them with bacteria.
Conclusion Questions:
1. What are the bacteria doing inside the termite? Termites ingest wood or plant
material, which is made up mostly of cellulose. “The symbiotic gut protists (lower
termites) or bacteria (higher termites) metabolize cellulose for the termites.” 4 The
protists or bacteria are necessary in the metabolization of the cellulose, because
termites do not natural have cellulase, the enzyme required for the digestion the
cellulose. Without the bacteria or protist, the termite would not survive.
2. How does the bacteria survive metabolically? The protists depend on
spirochete bacteria for survival. Bacteria attach themselves to the protist and
continuously propel it forward, keeping the protist from falling out of the termite.
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3. Why would the termite “tolerate” these masses of organisms? Termites
acquire glucose and other materials produced from the metabolism of cellulose so
they tolerate the bacteria in order to obtain these nutrients. Termites cannot digest
cellulose without the symbiotic relationship between them and the protist or
bacteria.
4. What could be the selective advantages for the inhabitants? If a particular
protist or bacteria was able to move faster it would be able to get to the wood
particles faster or if it was able to break down wood faster it would metabolize the
cellulose faster for the termite. It is all about survival of the fittest. The faster and
stronger will have an selective advantage over the competition.
5. How many kingdoms might be represented in this relationship? The general
taxonomy of termites is Kingdom Animalia, Phylum Arthropoda, Class Insecta,
and Order Isoptera.6 The symbiotic relationship is comprised of 3 Kingdoms: the
Animalia representing the termite, the Plantae representing the wood, and the
Protista representing the bacteria.
6. How might the microbes pass from one generation of termite to the next? The
bacteria is passed from parent to offspring by regurgitation of food orally or by
defecation anally.
7. What significance is the termite community to the earth?
4
http://www.biology.iastate.edu/intop/1Australia/Australia%20papers/EcolAusTermites%20.htm
http://www.biology.iastate.edu/intop/1Australia/Australia%20papers/EcolAusTermites%20.htm
6
http://www.biology.iastate.edu/intop/1Australia/Australia%20papers/EcolAusTermites%20.htm
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a. Without them there would be piles of dead wood covering forest floors,
which could increase bacteria production and or forest fires.
b. Termites are the most important decomposers in dry environments
because of their ability to recycle nutrients, form soil, and retain moisture.7
c. Termite symbiotic relationships with bacteria have been studied for their
similarities with human’s relationship with its internal bacteria. According
to Margulis, “the same fast-swimming spirochete bacteria that keep
Mixotricha paradoxa from falling out of the termite may also have played
a role, for example, in the development of motility in human sperm cells,
when long ago symbiotic mergers between the bacteria and the sperm cells
created the tail that propels the sperm through the reproductive tract.”8
d. Scientist have hypothesized that pathogens have played important
selections forces that “favored the evolution of complex insect societies”
and this has been studied by “focusing on the adaptations that termites
have evolved in order to resist disease.”9
8. Definition of Symbiosis: One living in the other in order to help it.
Questions: 1. How do the termites harvest the fungus?
2. How do bacteria inside termites fix nitrogen?
3. Why do the bacteria ferment CO2,ethanol, and acetic acid?
To break down the cellulose, termites enlist the help of a variety of microorganisms.
Some termites, for example, dig tunnels in the wood, then inoculate the tunnels with
fungi that grow on the wood. These termites then eat the fungi, not the wood itself.
What microbiologists find more interesting are the termites that contain, within their
digestive tracts, symbiotic microorganisms that digest the cellulose that the termites chew
and swallow. Even more fascinating to microbiologists is the fact that these
microorganisms themselves can survive only because of even smaller symbionts that live
on and within them, without which they would not even be able to move.
The termite's dependence on nitrogen-fixing bacteria to supply its nitrogen and on
protozoans such as Trichonympha sphaerica to digest cellulose is an example of
endosymbiosis, a symbiotic relationship with an organism that lives inside the body of
the host organism (in this case, within the hindgut of the termite).
Theoretically, the protozoan produces the cellulolytic enzymes that digest the cellulose.
The picture is more complicated than this, however, for T. sphaerica itself is unable to
digest cellulose with out the aid of bacteria that live within its body; in other words, the
protozoan has its own endosymbionts.
Certain hindgut ciliates such as T. sphaerica also demonstrate another form of sybiosisectosymbiosis, a symbiotic relationship with organisms that live outside its body. Recent
7
http://www.biology.iastate.edu/intop/1Australia/Australia%20papers/EcolAusTermites%20.htm
http://inpress.lib.uiowa.edu/poroi/papers/lopez010101.html
9
http://occawlonline.pearsoned.com/bookbind/pubbooks/tfc/medialib/Applications/termites.html
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advances in microscopy have shown that these ciliates are covered by precise rows
consisting of thousands of bacteria, either rods or spirochetes. If these bacteria are killed,
the protozoan in unable to move. Evidently, the protozoan does not use its cilia to move;
instead, the rows of bacteria move the protozoan like rows of bacteria move the
protozoan like rows of oarsmen in a boat.
http://occawlonline.pearsoned.com/bookbind/pubbooks/tfc/medialib/Applications/termites.html