“The bacteria therefore certainly has a potential to settle with us. Will it cause symptoms, an epidemic like the one we see elsewhere in the world? Maybe that’s the question “judge Claude Bragard, who is preparing to start a study specifically evaluating this risk for our regions. In any case, we know that the bacteria, in the 19th century, ravaged the Californian vine and is the reason why we no longer cultivate vines in the south of this American state.
But it is not the only bacteria to have wreaked havoc in agriculture. It is also to a bacteria (bacterial fire) that we owe to Belgium the disappearance of pear trees with high stem. And our potato fields also know, for example, brown or annular rot disease due to bacteria Ralstonia solanacearumimported via potato tubers. AFSCA must sometimes make uprooting, in order to prevent this bacteria from setting up with us, with economic impacts.
New path for the fight against diseases
Faced with these bacteria that can potentially lead to epidemics, a new wrestling path is taking shape: healing evil by evil. Clearly, fight against these bacteria … by other bacteria. For the past ten years, scientists have indeed made a discovery that has revolutionized the vision that we had of plants: like humans who have in their intestine billions of microorganisms having an effect on health, plants also have such a “microbiota”, very important for its growth.
Two Belgians detail the secret weapon of plants to disgust herbivores
“This discovery of the microbiota of the plant upsets our understanding of it. It shows that we must also consider the plant with all the microorganisms that compose itsummarizes Claude Bragard, professor at the Earth and Life Institute of the UClouvain. Of course, the plant is not going to eat with a mouth like us, but the plant feeds mainly at the start of its roots. This component is the rhizosphere. All these microorganisms (bacteria, fungi) in combination with the root play an extremely important role in the food of the plant, but also in resistance to water stress. Around the roots are microbial biofilms – bacteria – specially adapted to this location. The plant can select in this microbial population around the roots of bacteria which are capable of passing via the transport systems of the plant (xylem and phloème) to the upper parts of the plant. We will then find these microorganisms in the leaves, in the stems, in the reproductive organs, in the flowers … “
Experiments show that without microbiome, a plant grows much slower. This stimulates the nutritious elements, helps water absorption but also resilience to diseases, the specialty of Claude Bragard. In general, scientists are now starting to understand what are the main types of bacteria associated with plants, but also what are their arsenals. Because these bacteria have very diverse means of attacks against the other microorganisms of the plant. The idea would ultimately be to use them as a means of improving the plant or fighting bacteria destroying crops.
War with syringes of toxic molecules
In a study published this Friday in Nature Ecology & EvolutionProfessor Bragard’s laboratory precisely reveals the weapons deployed by a cousin bacteria from that destroying European olive trees and responsible for wheat stream, Xanthomonas translucens. Concretely, this bacteria Xanthomonas is capable of invading the leaves of cereals but also of carrying out a real war on other bacteria for these resources. To win, this bacteria has developed a series of mechanisms that allow it to kill or inactivate other bacteria sharing the same environment.
Belgian researchers discover “two surprising things” on our brain: “scientifically, such remote control of the microbiota was unthinkable”
“They have a fabulous secretion system: it is as if the bacteria developed a kind of syringeenthuses the scientist. This allows him to go and inject into the body of bacteria next to the molecules that have the capacity to kill. We have marked these bacteria and we can follow them. We even have videos where we see the bacteria that are killed and explode! We were also able to show what the genes were involved in the development of this secretion system. The pathogenic bacteria is therefore able to interfere directly with the microbiota of the plant, and partly inactivating it. It is able to interfere with these good bacteria or these good fungi present in combination with the plant and eliminate them where it wants to be active, that is to say in the XYLEM, the element which allows the plant to absorb water. A bacteria that eats the xylem will cause the plant wilting and drying out. “
The general idea would then be to take advantage of bacteria of this type and their “superpowers”, to attack other harmful bacteria this time to certain plants and cultures, using, in order to be careful, microorganisms present locally, at the scale of a plot or a “agro-system”.
“Working with the living is complicated”
Which would reduce the use of conventional fungicides. “We do not have a direct application yet, but a better understanding of all these competition mechanisms between bacteria will undoubtedly help to better understand and manage plant diseases differently. We are convinced as well as the microbiota of cereals, where we also find bacteria with similar mechanisms but this time beneficial to the plant, can be worked to improve resistance to disease. But that remains complex because the fungicides are extremely effective. In addition, working as here with the living is much more complicated. “
The most logical mode of application would in any case be acting via the plant, by coating the seed of a set of bacteria, which would be associated with the emerging roots, would develop and settle gradually in the plant, and return to competition with the micro-organisms of the soil more harmful to the plant.
