The predator-prey interactions between protists and bacteria in the wheat rhizosphere

Research output: Book/anthology/dissertation/reportPh.D. thesis

Abstract

The concept of "One Health" links human health to the well-being of ecosystem structures like soil, plants, and animals. It is suggested that these ecosystem structures are linked by the microbes.

These microbes therefore play an important part in the health of these ecosystems and thereby the One Health.
In addition, microbes such as bacteria, fungi, and protists impact the performance of agricultural crops, either by enhancing or inhibiting growth through various interactions. In particular, protist-bacteria predator-prey interactions will result in nutrient turnover and availability through the microbial loop. This nutrient availability will lead to increased crop growth. Additionally, the protist-bacteria interactions result in the production of a vast variety of volatile organic compounds (VOCs) with different impacts on soil health and crop performance.

The aim of this thesis was to improve the understanding of protist community composition and the protist-bacteria interactions in wheat. Additionally, the goal was to further the understanding of the volatile organic compounds (VOCs) production during protist-bacteria interactions. This was done by 18S rRNA sequencing of the soil samples from the UCPH Growth Chamber trial 2020 and establishing a protist culture collection for observing prey selection and VOC production.

The results of this thesis showed that the protist community composition is influenced by the rhizocompartment, wheat variety, and plant height. Additionally, qPCR showed a higher amount of protist in Rembrandt plants. The dominating protist subdivisions of the soil of the UCPH Growth Chamber trial 2020 were Cercozoa, Gyrista, Ciliophora, Clorophyta, and Discosea. A protist culture collection of 165 monocultures was established. A significant difference in the bacteria community of the cultures was found between soil sample rhizocompartment origin underlining how robust the rhizosphere effect is. Additionally, results showed no difference in the bacterial community composition of the protist \textit{Spumella} cultures of two different rhizocompartments suggesting that the protist is selecting for specific bacterial prey. Finally, time was found to be the strongest factor affecting the VOC production followed by the predator or prey presence. Additionally, results indicated that\textit{ A. castellanii} is producing squalene and that \textit{C. steinii} is producing 1,1,2-trimethyl-cyclohexane. In the end, these results can be used to develop innovative strategies for improving soil health and agricultural productivity and thereby the One Health.
Original languageEnglish
Number of pages150
Publication statusPublished - 2024

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