Team:Evry/Policy and Practices/Safety/Symbiosis

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When we first started to work on Pseudovibrio denitrificans, we were very interested by the fact that it was living inside a sponge: if the bacteria had a symbiotic relationship with the sponge, then it may not be able to live outside its host, and hence the symbiotic relationship would provide an efficient biological containment of the GMMO.
We read the literature about the two organisms, and soon discovered that Pseudovibrio denitrificans had probably no symbiotic relationship with the sponge: even though the microorganism can be found in the microbial florae of the sponge, some strains of denitrificans can also be found in seawater and in other organisms.

We still decided to work with Pseudovibrio, even though it wasn't symbiotic with its host, because of its other interesting characteristics : - we wanted to introduce a marine bacteria in iGEM, in order to tackle the huge problem of water pollution (?) - this "denitrificans" bacteria appeared to already have a system that allowed it to degrade and use nitrite as a source of energy - others... ? - and since it was already part of the microbial florae of the sponge, we thought that our GMMO had a fair chance to be able to live and survive inside the sponge – or at least a better chance than a bacteria that had never been seen inside the sponges, which meant that we could use the huge filtration power of the sponge to our advantage. Expliciter ?

And though we knew that our bacteria could live outside the sponge, the idea of a symbiosis stuck. Throughout the summer, we kept wondering: what is it WAS symbiotic with the sponge? We discovered that many bacterias, if not Pseudovibrio, had been studied and were thought to be symbiotic with sponges. In many papers, researchers state that they have found a micro-organisms to be specific to sponges, and sometimes symbiotic with them. In 2002, Hentschel & als. mentioned different symbiotic relations that have been found between sponges and micro-organisms, like nutrient acquisition and processing of metabolic waste. We then thought that it could be very interesting to either engineer Pseudovibrio to make it symbiotic with its host, or to use our Biobricks in a symbiotic bacteria.

However we discovered that there were actually very few papers that mentioned symbiotic GMMO, or symbiosis as a possible biological containment, and we decided to research and discuss ourselves whether symbiosis could be an efficient biological containment of GMMO.

1) Could we engineer the bacteria so that they would become symbiotic with the sponge?

Our first question was whether it was possible to transform Pseudovibrio denitrificans to make it symbiotic with the sponge – by symbiotic, we here mean that the bacteria should be unable to live outside its host.
To engineer such bacteria should be a priori possible with a better knowledge of the sponges and of the micro-organism. We currently don't know Spongia officinalis nor Pseudovibrio denitrificans well enough, since they were rarely studied. But we could for example search for a nutrient used by Pseudovibrio that would be secreted by the sponge ; then we would try to identify the genes in the bacteria's DNA that are involved in the biosynthesis pathway of this nutrient. We would then simply need to knock-out the genes coding the synthesis of this nutrient in the bacteria, and obtain an auxotrophic strain. This bacteria would not be able to grow without an external source of this nutrient: it would be able to grow in the sponge which produces this nutrient, but not in seawater where it wouldn't be able to find it.
In such a system, the host sponge would provide to the bacteria a necessary element for its growth and survival, and this would be the basis of a symbiotic relationship between the two organism, beneficial to the bacteria.

But would it really be sufficient to contain the GM bacteria inside its host, if we were to put the sponge in the wild?

2) Could symbiosis be an efficient containment system?

Our idea is that symbiosis could be an improved biological containment system. Usually, biological containment imply that the genetically engineered organism need to be given a nutrient that is only found in the lab in order to survive. But if the nutrient was produced by a host organism rather than by scientists in a lab, then we wouldn't need to have scientists feeding the micro-organism everyday, and we wouldn't need to keep the organism inside or near a lab. Theoretically, the host organism with the modified bacteria could be released in the wild without any risk of bacteria leaving the host, since they need the nutrient produced by the host.

However ...[not finished]