Teredinibacter turnerae

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Courtesy of Dr. Grace Lim-Fong. Picture taken at the Zoological Museum of Keil

Characteristics of the symbiont/pathogen

Located in the proteobacterium family, Teredinibacter turnerae are gram-negative rods that have polar flagellum for mobility. The genome of T. tunerae has almost been completely sequenced, containing about 5 million base pairs. It is closely related to Saccharophagus degradans.

Characteristics of the host

Commonly known as "shipworms" because they digest the wood immersed in salt water, Lyrodus pedicellatus are small salt water clams with small shells. Even thought they look like worms, they are not actually worms but molluscs. There are 300 species of Teredindiae, the shipworm family, which all have a Deshayes. Deshayes is a special organ where the digestion of cellulose (wood) occurs.

"Lyrodus pedicellatus (shipworm)" [1]

Host-Symbiont Interaction

The symbiosis between T. turnerae and L. pedicellatus is assumed to be a mutualism because there is no direct evidence supporting that T. turnerae benefits from the relationship.

T. turnerae has 2 enzymes important for L. pedicellatus. T. turnerae has cellulase which breaks down cellulose, the carbohydrate found in wood. Since this metabolism occurs in teh Deshayes of the shipworm, evidence supports that T. turnerae thrives in the special organ of the shipworm. T. turnerae also undergoes nitrogen fixation and has the enzyme nitrogenase to break down nitrogen into ammonia. Nitrogen fixation gives L. pedicellatus a source of nitrogen.

Studies have shown that T. turnerae are endosymbionts and are obligative faculative. This is due to the fact that T. turnerae have not lost any of its genes so it is able to thrive outside L. pedicellatus, even though there is has not been any evidence supporting that T. turnerae has been found in an environment outside L. pedicellatus.

Molecular Insights into the Symbiosis

Recently there has been studies focusing on the important enzyme used to by L. pedicellatus. CelAB (cellulase), the enzyme used by shipworms to break down the cellulose is found to have an optimum pH of 6 and an optimum temperature of 40 degrees Celsius. This means that the host must have these conditions in their Deshayes. On the molecular level, CelAB is the protein that is encoded by the cellulase gene that all T. turnerae.

Also, there has been a recent discovery in the genome of T. turnerae that has not been found anywhere else. Approximately 7% of the genome has metabolite pathways that have been found to have antibiotic properties similar to Streptomyces which leads to a benefit in medical research to kill of pathogens in humans.

"Genome of T. turnerae"

Ecological and Evolutionary Aspects

It is assumed that the host had engulfed T. turnerae. Focusing on the genome of T. turnerae, there have been no deletions suggesting that they do not have to be completely dependent on L. pedicellatus. However, there has been no known evidence suggesting that T. turnerae is a free-living organism like S. degradans. Even though no evidence has been found, it makes sense to suggest that T. turnerae can live in a free-living environment because it has all the genes necessary to survive and thrive outside L. pedicellatus.

Recent Discoveries

Describe two findings on the symbiosis published within the last two years.

References

[Sample reference] [[2] Seemanapalli SV, Xu Q, McShan K, Liang FT. 2010. Outer surface protein C is a dissemination-facilitating factor of Borrelia burgdorferi during mammalian infection. PLoS One 5:e15830.]

Edited by [Ahron Flowers], students of Grace Lim-Fong

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