Difference between revisions of "Part:BBa K343007"

Revision as of 18:19, 5 November 2010

Photosensor generator
This part consists of TetR repressed POPS/RIPS generator (including RBS), NpSopII-NpHtrII-StTar (M-fusion) and a dual terminator.

Photosensor data sheets


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Background

This part constitutively expresses the protein from the coding sequence of BBa_K343003, which in turn makes E. coli phototaxic when exposed to the right conditions. The promoter is inhibited by TetR, which in turn will not be active in the presence of tetracyclin.
For more background information and theory behind the part that is expressed via this generator, see the part K343003. For further characterization se experience

Usage and parameters

The part requires retinal to work in E. coli. This can be achieved through adding retinal to the liquid growth medium and/or the plates. Currently we are doing experiments on whether the part also functions with an internal retinal source, i.e. retinal synthesis in E. coli. Once the retinal has been added to the media, the cells will have to be incubated in the dark for at least two hours. This is necessary in order to obtain maximum output when the modified phototaxic organism is exposed to blue light.

Compatibility

This brick has been tested in the following plasmids and strains:

Chassis: E. coli MG1655.

Plasmids: PSB1C3 (high-copy), PSB3T3 (low-copy).

Risk-assesment

General use

This BioBrick poses no threat to the welfare of people working with it, as long as this is done in at least a level 1 safety lab by trained people. No special care is needed when working with this BioBrick.

Potential pathogenicity

This BioBrick consists of three different parts: The first 224 amino acid residues come from the NpSopII gene from Natronomonas pharaonis, encoding a blue-light photon receptor with 15 residues removed at the C-terminal. The following 9 amino acids are a linker. The last part is HtrII fused with Tar from E. coli. The complex' first 125 amino acid residues come from HtrII and the remaining 279 from Tar [1]. NpHtrII is thought to function in signal transduction and activation of microbial signalling cascades [2].

A single article has been written about haloarchaea in humans indicating that these played a role in patients with inflammatory bowel disease [3], but there is no evidence that the genes this BioBrick is made from or any near homologs are involved in any disease processes, toxic products or invasion properties. They do not regulate the immune system in any way.

Environmental impact

The BioBrick does not produce a product that is secreted into the environment, nor is it’s gene product itself toxic. It would not produce anything that distrupt natural occurring symbiosis.

The BioBrick might increase a bacteria’s ability to find nutrients and as such ease its ability to replicate and spread in certain dark environments. On the other hand, the BioBrick is very large and this will naturally slow down its replication rate. Generally, we do not believe this BioBrick will make its host able to outcompete naturally occurring bacteria, simply because its function is not something that will give its host a functional advantage.

Possible malign use

This BioBrick will not increase its hosts ability to survive in storage conditions, to be aerosoled, to be vaporized or create spores. None of its proteins regulate or affect the immune system or are pathogenic towards humans and animals.

Results

Our results from the experiments with semi-solid agar confirms that the bacteria carrying a plasmid with the biobrick have a altered motility, most likely by an alteration in tumbling frequency, when exposed to blue light compared to the wild type MG1655.

The videomicroscopy indicates that bacteria carrying a plasmid with the biobrick travel father and in a more straight path than the wild type MG1655 when exposed to blue light with a wavelength around 500nm, Thereby suggesting a lowered tubling frequency.

Computeranalysis of videos recorded of swimming baceria containing this part, indicate that these bacteria have a tendency to swim towards the source of light, when exposed to a light gradient. A trackdiagram was constructed from the gathered data, and swimming bacteria tended to orientate their movement in the direction of the light source. This could mean that blue light acts as an attractant stimulus on the SopII-HtrII-Tar complex.

The stability of pSB1C3-K343007 is most likely <20 generations, however the stability of pSB3T5-K343007 was not determined.
Plasmids expressing K343007 does not seem to hinder the bacterial growth in any way.
For further information, raw data and background on the assays see [http://2010.igem.org/Team:SDU-Denmark/K343007 characterization of K343007] on our team wiki.
Sequence and Features

References

1. Jung KH, Spudich EN, Trivedi VD, Spudich JL. [http://www.ncbi.nlm.nih.gov/pubmed An archaeal photosignal-transducing module mediates phototaxis in Escherichia coli]. J. Bacteriol. 2001 Nov;183(21):6365-6371.
2. Mennes N, Klare JP, Chizhov I, Seidel R, Schlesinger R, Engelhard M. [http://www.ncbi.nlm.nih.gov/pubmed Expression of the halobacterial transducer protein HtrII from Natronomonas pharaonis in Escherichia coli.] FEBS Lett. 2007 Apr 3;581(7):1487-1494.
3. Oxley APA, Lanfranconi MP, Würdemann D, Ott S, Schreiber S, McGenity TJ, et al. [http://www.ncbi.nlm.nih.gov/pubmed Halophilic archaea in the human intestinal mucosa]. Environ Microbiol [Internet]. 2010 Apr 23 [cited 2010 Oct 26].
4. Derek L. Englert, Arul Jayaraman, Michael D. Manson,[http://www.springerlink.com/content/n386247071624387/fulltext.pdf Methods in Molecular Biology], 2009, Volume 571, 1-23.
   
5. Celltrack