Evaluation of the Interaction between the biocontrol agent Trichoderma atroviride and plant growth-promoting bacteria
Student/in: Anna Oberdanner, BSc
Termin: 19.08.2025, 15:00 Uhr
Ort: Seminarraum Biologie (Foyer)
1. Prüfer/in: Univ.-Prof. Dr. Mag. Susanne Zeilinger-Migsich
2. Prüfer/in: Nadine Präg, PhD
Vorsitzende/r: Prof. Dr. Christian Rinke
Interessierte Kolleginnen und Kollegen sind herzlich willkommen!
Abstract
Biocontrol agents (BCAs) such as Trichoderma atroviride and plant growth-promoting bacteria (PGPB) are well-known for their beneficial effects on plant productivity, health and protection against plant pathogens. Due to their putative enhanced beneficial effect in combination, these microorganisms are often combined in commercial formulations marketed as biopesticides or plant stimulants. However, the underlying mechanisms governing the interactions between T. atroviride and PGPB remain largely unexplored, particularly how these microbes affect each other.
To investigate these interactions, co-cultivation experiments both on solid and in liquid medium were established and optimized, as well as interaction assays allowing the communication only through volatile organic compounds (VOCs) were performed. Additionally, the responses of various bacterial strains to the presence of T. atroviride culture filtrates and its metabolite 6-pentyl-α-pyrone (6-PP) were analysed.
Our results demonstrated that T. atroviride and the selected bacterial species and strains engage in multifaceted interactions affecting each other’s growth and metabolism. On solid media, bacterial strains consistently inhibited fungal mycelial expansion, while fungal culture filtrates suppressed bacterial growth in liquid culture. VOC-mediated interactions between T. atroviride and Bacillus subtilis strains DSM10 and 168 induced notable morphological changes in the bacteria. A special emphasis was put on the effect of the interaction on the production of secondary metabolites (SMs) by the involved microorganisms, which were captured using high performance thin layer chromatography (HPTLC). In general, co-cultivations resulted in altered metabolite spectra. Some interactions stimulated SM biosynthesis, while others reduced it. For example, Paenibacillus polymyxa enhanced 6-PP production by T. atroviride upon co-cultivation on Standard 1 agar plates. Interestingly, expression of pks1, the responsible biosynthetic gene essential for 6-PP production in T. atroviride, remained unchanged during liquid co-cultivation with Pa. polymyxa but was downregulated with B. subtilis DSM10, B. subtilis 168, and Pseudomonas protegens, and upregulated during co-cultivation with Streptomyces rapamycinicus.
Moreover, bacterial growth was inhibited by 6-PP although concentrations up to 10 mM were required to affect some strains significantly. These findings underscore the complexity of microbial interactions and secondary metabolite dynamics.