Universität zu Köln

Elkatmis, Büsra ORCID: 0000-0002-0519-4380 (2026). Dissecting Multi-Layered Mechanisms of Plant Growth Promotion by Pseudomonas argentinensis SA190. PhD thesis, Universität zu Köln.

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Abstract

Plants are in constant interaction with their surrounding environment and are strongly influenced by it. Climate change-driven alterations in environmental conditions are causing significant and often unavoidable reductions in plant growth and productivity. Therefore, developing strategies to support plant growth and maintain yield under adverse environmental conditions has become increasingly important. In this context, plant growth-promoting bacteria (PGPB) have emerged as a promising solution to enhance plant growth and development. Notably, the identification of PGPB and understanding the mechanisms they employ have become particularly important due to their potential to support the development of stressresilient plants. To gain insight into these interactions, this thesis focuses on elucidating the multi-layered mechanisms underlying the plant growth-promoting (PGP) activity of the root endophyte Pseudomonas argentinensis SA190. The first study investigated the PGP traits, biochemical characteristics and stress tolerance capacity of SA190. We then constructed a transposon library to identify the key microbial traits underlying the PGP activity of SA190. Our results showed that biofilm mutants, particularly disruption of the wspC, rpoE, and fliD genes, resulted in reduced stable attachment to Arabidopsis thaliana roots and impaired PGP activity under PEG-induced drought stress. Secondly, we optimized the RATE-PCR protocol for SA190 to identify the genomic locations of Tn5 insertions. Since transposon mutagenesis generates random insertions in the bacterial genome, identifying the insertion sites allowed us to improve our understanding of SA190 genes and link specific genes to PEG-stress tolerance. The final study examined the impact of SA190 on Arabidopsis thaliana metabolism, with a particular focus on sulfur metabolism. We found that SA190 modulates sulfur metabolism and enhances tolerance to PEG-induced drought stress by improving glutathione (GSH)-mediated redox homeostasis. Collectively, the studies presented in this thesis provide insights into the multi-layered mechanisms underlying plant growth promotion by SA190 under PEG-induced drought stress. These findings improve our understanding of plant-microbe interactions under stress conditions and highlight the potential application of beneficial microbes and their mechanisms for the development of stress-resilient plants.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Elkatmis, Büsra belkatmi@uni-koeln.de https://orcid.org/0000-0002-0519-4380 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-813598
Date:	2026
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	CEPLAS - Cluster of Excellence on Plant Sciences
Subjects:	Life sciences
Uncontrolled Keywords:	Keywords Language Plant-microbe interaction English Drought stress English Glutathione English
Date of oral exam:	15 September 2026
Referee:	Name Academic Title Kopriva, Stanislav Prof. Dr. Hildebrandt, Tatjana Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/81359