Team:Valencia Biocampus/Project

Escherichia coli

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Pseudomonas putida

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Caenorhabditis elegans

An overview about our nematode

The main character of our work is a nematode known as Caenorhabditis elegans, from the Rhabditidae family. It was first used as an experimental model in Developmental Genetics studies, and nowadays is also used in other fields such as clinical biology, neurobiology and cell biology, being a good model to study Alzheimer disease, obesity, diabetes, and aging, among others

Another interesting thing is that it feeds on Escherichia coli. Its “favorite” strain is OP50, although we checked that it’s also able to feed on strain DH5α, the one used in all our molecular biology experiments.

Some advantages of C. elegans when compared with other model organisms are:

-Lifespan ranges between 2 and 3 weeks, so experimentation times are reduced.
-Its maintenance and study is cheap and simple (it is transparent, which facilitates microscopic observation).

-It is very small (1 mm), so it is possible to carry out experiments with a huge number of worms in a small Petri dish having a great statistical support.

Why use C. elegans as a transport?

When we were considering creating a new system for the transport of bacteria, we find different key advantages that made the nematode the best option. For example, C. elegans is able to move very fast around solid substrates (soil is, actually, its natural habitat) and also in agar, so it’s very useful for both lab experiments and real-environment tests.

His movement, in addition to being very fast, has two modes: random and directed.
When there is no attractant in the medium, C. elegans moves doing uncoordinated movements in several directions in what is known as 'random walk'.

The situation changes when there is an attractant in the medium. Here, our 'transport' begins to direct his movements to the focus of the substance (volatile or soluble) which acts as an attractant in a process known as 'chemotaxis' thanks to the amazing smell of our nematode. This allows us to “guide” the nematodes towards defined spots in irregular substrates.

Chemotaxis is the foundation to guide the transport of bacteria and is therefore the focus of experimentation with C. elegans, with the aim of finding the best attractant. This ability makes C. elegans a perfect 'bus' for bacteria.

Moreover, we found two pathogens (Yersinia pestis and Xhenorhabus nematophila) with the ability to form biofilms on C. elegans thanks to the proteins of the operon hmsHFRS. When genetically-engineered strains of commonly used bacteria such as Escherichia coli or Pseudomonas putida express this hmsHFRS operon, they have the 'ticket' to travel: they are able to adhere to the worm’s surface by means of forming a synthetic biofilm.

Expanding our knowledge about C. elegans...

Once we knew that C. elegans was the best option, we began to discover interesting things for further study.

There are several strains of our nematode. The one that drew our attention was called 'N2', which had a fairly interesting behaviour: under normal conditions, it eats individually, whereas under certain conditions (such as starvation), a social feeding behavior known as “clumping” is induced. But this phenomenon can also be induced if the expression of some particular genes is interfered. This fact gave us the opportunity to develop the first artificial symbiosis between worms and bacteria, based on the manipulation of the behaviour of C. elegans by simply nourishing it with transformed E.coli able to synthesize the iRNA.

With it, while C. elegans acts as transport, bacteria return the favour giving it the ability to eat in company.

Parts

Works?	Name	Type	Description	Designer	Length	Structure
	BBa_K1112000	Regulatory	fadA promoter + flp-21 iRNA	Pedro Luis Dorado Morales
	BBa_K1112001	Regulatory	pGlnA + hmsHFRS operon	Alba Iglesias Vilches
	BBa_K1112002	DNA	Cluster PHA	Alba Iglesias Vilches