To begin with, making a living from agriculture is not easy. On top of this, farmers often struggle with environmental obstacles that lead to losses of agricultural products. The loss of crops can be due to extreme weather, pathogens, herbivores, seismic activities and much more. In countries with weather similar to the one we experience here, in Switzerland, farmers have to battle a fierce enemy during the spring: frost. Each year, a large amount of crops in Switzerland are lost due to ice damage.
Another remarkable foe farmers combat are pathogens, such as bacteria that attack the plants, often undetectable until serious damage has been caused. Bacteria can damage plants in many ways: they can rot plant tissues, cause tumors, and even enter the plant and highjack its molecular systems for their own selfish gain to create nutrients consumable only by the bacteria. Some bacteria have even evolved to use cold nights experienced in Switzerland to their advantage, by using the frost to damage the plant and enter its tissue. A particularly interesting example of this type of plant pathogen is Pseudomonas syringae, a bacterium that exacerbates damage caused by low temperatures.
Pseudomonas syringae is a remarkable foe, particularly on fruits trees during the early spring. This species produces an Ice Nucleation Protein (INP), a protein that causes the formation of ice crystals on the plant at high sub-zero temperatures. These crystals damage the plant tissue, causing wounds that allow the bacteria to enter the plant. In the absence of such pathogens, the plant tissues can resist temperatures as low as -8°C without getting damaged.
The INP produced by Pseudomonas syringae are attached to the outer membrane of the bacteria. They interact with water molecules and rearrange them, permitting a faster formation of ice crystals at low temperatures.
Buds on fruit trees and young fruits are particularly affected by Pseudomonas syringae and cold temperatures. This combination can lead to astronomical agricultural losses. As an example, this year, in the Valais in Switzerland, farmers lost 85% of the apricot production because of the frost. The trees in this region are particularly exposed to these bacteria. Indeed, farmers water their plants using melting snow from the mountains. This water is however combined with the melting snow from ski stations. Unfortunately for the farmers, P. syringae are used to create snow more efficiently in the snow canons along the slopes. The farmers are therefore accidently spraying the pathogen onto their trees, causing the worsening of frost damage during cold nights.
Battling this pathogen is tricky. Indeed, the use of antibiotics, one of the more usual way to combat bacteria, is not advised in huge quantities as it could create strains with resistance. Also, spraying antibiotics on the crops themselves can expose consumers to ingest high amounts of antibiotics unknowingly.
A promising solution to combat P. Syringae would be to add different strains of Pseudomonas in the environment, causing a natural competition. We could equip the other strains of Pseudomonas with tools, such as Tailocins, to kill P. Syringae specifically.
For more information on this go check Joaquim’s article about Tailocins!
References
1. Gordon JE, Christie PJ. The Agrobacterium Ti Plasmids . Microbiol Spectr [Internet]. 2014 Nov 21 [cited 2021 Aug 27];2(6). Available from: https://journals.asm.org/journal/spectrum
2. Snomax – Snomax [Internet]. [cited 2021 Aug 27]. Available from: https://www.snomax.com/product/snomax.html
3. Abricots | Valais Suisse [Internet]. [cited 2021 Aug 27]. Available from: https://www.valais.ch/fr/le-valais/produits-locaux/abricots
4. Roeters SJ, Golbek TW, Bregnhøj M, Drace T, Alamdari S, Roseboom W, et al. Ice-nucleating proteins are activated by low temperatures to control the structure of interfacial water. Nat Commun 2021 121 [Internet]. 2021 Feb 19 [cited 2021 Aug 27];12(1):1–9. Available from: https://www.nature.com/articles/s41467-021-21349-3
5. Pseudomonas syringae — Wikipédia [Internet]. [cited 2021 Aug 27]. Available from: https://fr.wikipedia.org/wiki/Pseudomonas_syringae
