In 1976, Edward Jenner conducted his famed inoculation experiments leading to the invention of vaccines, and we are all now familiar with the basic concept: inoculation with dead, inactive, or attenuated material from the pathogen that helps our immune system develop some level of immunity against the active pathogen. Vaccines have been used to help animals fight pathogens too.

But imagine this: vaccinating an environment (e.g. soil) against pathogens, with the microbiome acting in lieu of immune cells.

That is essentially what Josephine Pasche and colleagues did in their recent paper published in Microbiome. They inoculated soil with compounds found in abundance  in the eggs or adult form of the pathogen, which shaped the microbiome of the soil/rhizosphere to favour microbes that produce enzymes that act against the pathogen.

So how does this work?

The nematode parasite Meloidogyne enterolobii – more commonly known as the guava root-knot nematode – infects a wide range of agricultural plants such as tomatoes. It is a global threat, and infection can lead to a 65% yield loss- and thus has serious implications for global food security.

Pasche and colleagues knew that 80% of the nematode’s cuticle is made of collagen, and there is high chitin content in the nematode’s eggs. They therefore mixed either chitin or collagen into soil samples before  planting tomato seedlings.

Following this, they exposed the soils to either a standard dose (5000eggs/plant) or high dose (50000 eggs/plant) of nematode eggs. They found that collagen reduced parasite egg counts by 66% and 84%, respectively, for the soils where standard and high doses of the parasite were added. Similarly, chitin reduced egg counts by 60% and 81% respectively for standard and high doses.

It has been deduced that the addition of collagen and chitin enriched certain beneficial microbes in the soil that are known for producing chitinase and collagenase enzymes. These microbes are from the Steptomyces, Bacillus and Kitasatospora bacterial genera and Phialemonium fungal genus.

Plant health also improved with the addition of collagen and chitin (chlorophyll content increased by 170%, and shoot and root biomass increased by 330%), implying that the plant’s own defence mechanisms may also be activated to some extent.  

View the video summary of the original paper

 In a world where global food security is more and more at risk due to conflict, climate change and disease, it is extremely important to be able to protect the agricultural industry. These days, sustainable, responsible pest and disease control techniques are being sought more frequently. Amending the soil with collagen and chitin – effectively vaccinating the soil to enrich for beneficial microbes –  seems like it could answer these needs, although more extensive tests will need to be conducted before this method could become standard practice.

Poster image credit: Image by Aritha from Pixabay