Interactions of <i>Burkholderia terrae</i> with soil fungi:Mechanisms, gene expression patterns and ecological behavior of <i>Burkholderia terrae</i> BS001 during its interaction with <i>Lyophyllum</i> sp. strain Karsten and <i>Trichoderma asperellum</i> 302 in soil

Abstract

Even though soil is a nutrient-limited environment, there are zones of high microbial activity. Mainly zones that are influenced by plants, fungi, or a combination of both, are of interest. The mycosphere (niche under the influence of fungi) is the zone where, in particular, bacterial-fungal interactions take place. In my thesis, I studied the interaction of the soil bacterium Burkholderia terrae with Lyophyllum sp. strain studied Karsten and Trichoderma asperellum 302. In particular, I studied the strategies used by B. terrae to interact with soil fungi, and its behavior in relation to the two fungal species. The analyses revealed that B. terrae possessed the necessary genetic information that is required for successfully interacting with fungi, including the flagellar motility, chemotaxis, protein secretion systems, biofilm formation and secondary metabolite synthesis genes. I also observed that under soil-mimicking conditions in the presence of Lyophyllum sp. strain Karsten, B. terrae expressed genes responsible for chemotaxis, energy generation and oxidative stress response. B. terrae was also able to sense the presence of fungi and fungal released compounds (chemoattractants) including oxalic acid and glycerol, in its surroundings by showing a chemotactic response towards these. In terms of the physical interactions with the fungi, B. terrae was able to attach to one of the anchoring sites present on the cell envelope of Lyophyllum sp. strain Karsten. The work presented in this thesis adds to the understanding of bacterial interactions with fungi in soil and highlights the importance of bacterial-fungal interactions for soil quality and health