Team:Poitiers/Description
Description
Pollinating species
Pollinating species, and especially honey bees, are responsible for the abundance and diversity of our food, as well as for most of the ecosystems. Indeed, they allow the pollination of 80% of plant species, and among them, 35% of food plants. Nowadays, a lot of edible plants and food plants rely heavily on the pollination, tying the diversity of our diet to the well-being of these insects. Therefore, it is of key importance to keep pollinating species, and especially honey bees alive and healthy. Unfortunately, honey bees are in trouble: there has been recently a sustained loss of bees each year. Indeed, there is a loss of approximately 30% of bees population each year, especially around winter [1].
Consequences
This huge diminution of the bee population has social, economic and environmental consequences.
Vespa velutina nigrithorax
Vespa velutina nigrithorax (Vvn) , also called Asian hornet is an invasive species in France and Europe. It arrived in the south-west of France by boat while a pottery importation. Coincidentally, the conditions were perfect for the survival and the spread of this insect on our territory.
The issue with this predator is that its diet is essentially composed of Honey bees, depending on the surrounding environment [2]. But it also eats other pollinating species.
Moreover, our European bees (Apis mellifera mellifera) aren’t used to this predator. They haven’t developed an efficient fighting method against the Asian hornet yet [3]. This makes them more vulnerable. Plus, when Asian hornets are hovering around the hives, honey bees mass together at the entrance of the hives to protect them and prevent hornets from entering the hives [3]. But by doing that, bees are less searching for food. So when winter comes, the hives are slowly dying by lack of food. That is partly why there is such a decrease in the honey bees population during winter.
Fighting methods
For the moment there are only two possible fighting methods against the Asian hornet in Europe:
- To find and destroy the nest
- To trap the Asian hornet
Finding and destroying the nests
This could possibly be the best fighting method against this invasive species, if only it was simple. One nest destroyed equals thousands of Asian hornets less. But the thing is that it is hard to spot nests at the right time of the year. Indeed, the right period is between the beginning of Spring until the end of Autumn. This period corresponds to the creation and the expansion of nests. In winter, nests are abandoned and will never be reused. But from Spring to Autumn, trees have leaves behind which Asian hornets hide their nest. These nests can even be built up to 15m high up in trees [4][5][6], making them harder to spot.
And even if these nests are spotted, to destroy them, we first need to reach them (which isn’t always possible), and to inject pesticides and insecticides inside. Being extremely volatile, these products usually end spreading in the nature, which isn’t good at all for the environment.
Trapping the Asian Hornet
The only remaining viable alternative to biocontrol the Asian hornet is to trap them in order to reduce their impact on bee population. Asian hornet traps are based on the creel principle. The size of the entrance is calibrated on the size of the hornet, so that it can easily enter but can’t exit. A simple bottle cut in half, and the upper part put upside-down can serve as a decent trap. However, in the case of bottle traps, the size of the entrance isn’t selective for the Asian hornet.
But the issue with these traps is the bait. They are usually made of a mix of honey, red syrup, wine and beer. Unfortunately, this kind of bait does not only lure Asian hornets, but also other insects like bees and other pollinating species.
So by using this kind of traps, people worsen the issue instead of solving it…
Specific bait
We are convinced that there is a need of a bait which would be specific to the asian hornet. The efficiency of the current traps would be enhanced, and the unnecessary trapping of other insect species would be put down to zero.
Sexual pheromone
The use of molecules from the sexual pheromone of the Asian hornet as a bait imposed itself as an obvious choice to begin our research. Indeed, recent articles pointed out that a particular mix of 4-oxooctanoic acid and 4-oxodecanoic acid, which are two components of the sexual pheromone, induced strong electroentennal responses on male Vespa velutina, and thus could be a strong attractant for them [7]. More recent field testings showed that this particular mix is actively attractive for male Vespa velutina (E.Darrouzet et al., upcoming article).
To produce these molecules, we designed a 2 steps process, in which we would use an already modified bacteria strain to overproduce free fatty acids. These free fatty acids could be used to supplement the culture medium of another bacteria strain. We would modify this bacteria strain to integrate and use these free fatty acids to produce the 4-oxooctanoic and 4-oxodecanoic acids.
Alarm pheromone
Another interesting approach would be to use a molecule coming from the alarm pheromone of the Asian hornet, the 2-nonanone. This molecule is present in the venom of the Asian hornet, and has already proven to induce strong electroentennal responses on Vespa velutina individuals, as well as triggering attacks [8]. To produce this molecule, we would modify a bacteria strain to inhibit the lipid degradation, in aid of the methyl ketone producing pathway [9].
Synthetic Biology production benefits
Producing these molecules by classical chemistry requires a lot of polluting solvents in almost all of the producing steps. Thus, the chemical production of these molecules is long, polluting and expensive. Synthetic biology allows us to avoid using these solvents in every production step, but instead, only at the beginning when modifying bacteria. After that, bacteria only need a growth medium and some sugar. Thus, this method is cheaper and more ecological than classical chemistry.
This method can be used in this domain but also in a lot of chemical productions, especially in specific fatty acids production. That’s why it is so interesting to use synthetic biology.
Regulation
In order to control the production of our molecules, we decided to use a strong arabinose inducible promoter to ensure that all the enzymes of the modified pathways would only be available in the bacteria strain when we decided to. This way, even if the products are toxic for the strain, we would control whenever it is produced.
Why this project?
All the team members were aware of the Asian hornet issue and observed an increasing number of this invasive insect in our gardens each year.
So we decided to try to work on a subject about Asian hornet. And the more we learned about the issues caused by this insect, and the lack of effective fighting method, the more we wanted to find a specific method to fight against this invasive species.
Moreover, we not only realized the usefulness of such a project, but also its feasibility.
Indeed, the fund raising would be facilitated, because the Asian hornet issue is already well mediatised, people are globally aware of it.
We also saw that the research about specifically attractive molecules for the Asian hornet was very recent. Plus, we read recent articles, talking about specific bacteria strains which are able to produce molecules which are structurally near the molecules that we want to produce. These are the reasons why we were eager to pursue this subject.
References
[1] Chauzat MP, Cauquil L, Roy L, Franco S, Hendrikx P, Ribière-Chabert M., Demographics of the European apicultural industry. (2013) PLoS One, 8, 1-13.
[2] Rome, Q., Perrard, A., Muller, F., Villemant, C., Monitoring and control modalities of a honeybee predator, the yellow-legged hornet Vespa velutina nigrithorax (Hymenoptera: Vespidae) (2011) Aliens: The Invasive Species Bulletin, 31, 7‑15.
[3] Mariangela Arca, Alexandros Papachristoforou, Florence Mougel, Agnès Rortais, Karine Monceau, Olivier Bonnard, Pascal Tardy, Denis Thiéry, Jean-François Silvain, Gérard Arnold, Defensive behaviour of Apis mellifera against Vespa velutina in France: Testing whether European honeybees can develop an effective collective defence against a new predator (2014) Elsevier, 106, 122-129.
[4] Q. Rome, F. J. Muller, A. Touret‐Alby, E. Darrouzet, A. Perrard, C. Villemant, Caste differentiation and seasonal changes in Vespa velutina (Hym.: Vespidae) colonies in its introduced range (2015) Journal of applied entomology, 139, 771-782.
[5] Quentin ROME, Franck MULLER, Olivier GARGOMINY and Claire VILLEMANT, Bilan 2008 de l’invasion de Vespa velutina Lepeletier en France (Hymenoptera, Vespidae) (2009) Bulletin de la Société entomologique de France, 114, 297-302.
[6] Claire Villemant, Jean Haxaire and Jean-Claude Streito, La découverte du Frelon asiatique Vespa velutina, en France (2006) Insectes, 143, 3-7.
[7] Ping Wen, Ya-Nan Cheng, Shi-Hao Dong, Zheng-Wei Wang, Ken Tan & James C. Nieh, The sex pheromone of a globally invasive honey bee predator, the Asian eusocial hornet, Vespa velutina (2017) Scientific reports, 7, 1-10.
[8] Ya-nan Cheng, Ping Wen, Shi-hao Dong, Ken Tan and James C. Nieh, Poison and alarm: the Asian hornet Vespa velutina uses sting venom volatiles as an alarm pheromone (2017) The Company of Biologists, 220, 645-651.
[9] Ee-Been Goh, Edward E. K. Baidoo, Jay D. Keasling and Harry R. Beller, Engineering of Bacterial Methyl Ketone Synthesis for Biofuels (2011) AEM ASM, 78, 70-80.