Our biodetection system is composed of a sea sponge and of a genetically modified bacteria strain that lives inside this sponge. During our research, we have often wonder about the best way to safely contain our modified bacteria if Sponge Patrol was ever to be used by industrials or water treatment plants, and thought about many problems and several potential solutions.
In order to safely contain the bacteria out of the environment, we could put them in a hermetic aquarium, with a filtration system that doesn't let any bacteria leave the aquarium. We would then need to put samples of the water we want to test in the aquarium.
But we also thought of other ways to use our sponge-bacteria system, such as releasing them in the oceans in regions that are likely to contain important concentrations of pollutants. The release of Genetically Modified Micro-Organisms (GMMO) in the environment is very controversial though, as it raises several safety issues. As of yet, there has been no legal release of GMMO in the oceans. But then we thought of a new possible way to contain the GMMO: what if we designed an epibiosis strain of Pseudovibrio denitrificans, such that it would not be dependent from its host and unable to live away from it? Would such an epibiosis be a safe containment system?

In order to better understand the legal and safety issues related to the release of GMMO in sea water, and to define whether epibiosis could be an efficient containment system of GMMO, we digged into the litterature and discussed those points together.

• What are the risks involved in the release of GMMO in the oceans?

• Can epibiosis be an efficient containment system?

As far as we know, releasing GMO or GMMO in the oceans has presently not been legalized anywhere in the world. There is a Canadian campany that is breeding genetically modified salmons, AquaBoutny Technologies, but the fish are physically contained in off-shore water tanks. These fish are not yet commercialized, though the company has asked for an authorization to sell their product.

Since we lacked actual examples of GMMO released in the sea from which we could have retrieved data, we decided to first study some experiments that have been done in soils in order to evaluate the impact of released GMMO in the environment.
In 1993-1994, Ian Thompson and his team conducted a research at the University of Oxford Wytham Field Station, where they released free-living GM bacteria in fields. For their experiment, they mostly used an engineered Pseudomonas fluorescens whose presence they could easily detect in samples taken from the fields. Thompson reports that the GM bacteria survived a whole season in the field, before disappearing because it couldn't compete with the existing, natural bacterias present in the soil and in the plants. They also noticed that the bacteria survived better in some environments than others: they survived longer in the glasshouse where there was less competition, and they became as numerous as natural bacteria in sugar beets for a while. The overall result, though, was that the GM bacteria did not survive in the long-term, because it could not compete with the existing microorganisms.
Other similar experiments have been made in different soils, and the result so far has always been the same: the GM bacteria was not able to compete with natural species, and rapidly disappeared.

Thompson also co-founded a company, Microbial Solutions, where some GMMO are used as biosensors in water. Since the release of GMMO in water outside labs has not been authorized, they are only used in physically contained environments. But as reported in the report of the 2013 Workshop on "Synthetic biology: containment and release of engineered micro-organisms", Thompson believes than even if they were released in the environment, these bacterias would also be unlikely to compete with natural species, because realizing the additional function - in this case, sensing toxic compound in industrial waste streams and signal their presence - would be costly in terms of energy for the cells. It would be a loss of energy for the bacteria, for which they would not gain any advantage. Those engineered bacterias would thus be less competitive than bacterias that do not realize this function.

This lead us to believe that for the same reason, our engineered Pseudovibrio would have a very low chance of survival if released in the environment. In fact, it probably wouldn't even live very long inside the sponge, if we put our bacteria in presence of all the other microorganisms that live inside Spongia officinalis. Because of its additional biosensing function, our strain would probably either get rid of the function, or disappear given a certain amount of time.
The fact that our bacteria may not survive for a long period of time is necessarily a problem if we want to use the sponge as a biosensor, though. We would simply need to inject new GM Pseudovibrio in the sponge every time we want to test the water. The time it would take for the bacteria to produce fluorescent proteins if the water was polluted should indeed be shorter than the time it would take for other bacterias to overcome our Pseudovibrio.


However, the low-probability of survival of our GM bacteria in the long term does not suffice to say that releasing it in the environment would be harmless. First, because the possibility that the engineered Pseudovibrio would survive in the sponge despite our expectations is not null. Second, because even if the bacteria strain doesn't survive for a very long time, it may still have negative consequences on its environment. And the environment we have to take into account is not only the sponge and its microbiome, but also other marine species since the bacteria is not, as of yet, contained inside the sponge.

To evaluate the consequences of a GM micro-organism on an ecosystem as complex as the ocean, though, is near impossible because we don't have enough data to make a relevant model. The behavior and impact of the micro-organism could moreover be highly variable given the specific conditions of each location. The only data we can try to rely on, is our knowledge of the DNA of the micro-organism: knowing the different genes in the bacteria's genome, we may be able to predict whether it could be harmful. For example in the Sponge Patrol project, the inducible promotors and the genes coding for fluorescent proteins we want to put in Pseudovibrio are unlikely to have a negative effect on the ecosystem.
But we cannot be certain that no unexpected effect or no mutation will occur, that could be detrimental in some way. Very often in synthetic biology, scientists don't get the expected result when they design and engineer a biological system with new functions. One example is that gene expression can change a lot depending on the context. Another is that two parts put together in a construction can have an emergent, unpredicted function, instead of just the additional functions of both the parts. Since the sea is a very rich and hardly known ecosystem, we truly can't know if the release of our bacteria could have detrimental effects.