The role of cross-kingdom biofilms in the epiphytic growth of Zymoseptoria tritici

Septoria leaf blotch (STB), caused by the fungal pathogen Zymoseptoria tritici, is one of the biggest threats to wheat production globally. Recently, it has been shown that this pathogen can survive for extended periods and form biofilms on the leaf surface prior to infection. However, it is currently not known how the fungus obtains nutrients during this period. In this thesis, I test the hypothesis that fungal nutrient acquisition during this growth phase is facilitated by interaction with bacteria found on the leaf surface. Many bacteria that inhabit the leaf surface (the ‘phylloplane’) are known to secrete metabolites, such as enzymes and surfactants which improve nutrient availability. Here, I show that Z. tritici is able to benefit from growing in co-cultures with field-isolated bacteria and use confocal microscopy to show that it can form cross-kingdom biofilms with some bacteria in vitro. I also use stimulated Raman scattering microscopy to track and quantify the flow of deuterated nutrients from plant to fungus. This novel method confirmed that Z. tritici is able to take up nutrients directly from the plant during its epiphytic growth phase. Treatment of these deuterated plants with common metabolites produced by phylloplane bacteria, such as lipase and surfactin, revealed that Z. tritici benefits from increased nutrient uptake in the presence of low concentrations of these compounds, but these benefits are lost at higher concentrations. I also used in vitro assays to confirm that bacterial isolates that form associations with Z. tritici are able to produce secretory lipase and surfactants, which provides a possible mechanism for their interaction in planta. Finally, I attempt to show an effect of co-inoculation of Z. tritici with bacteria and metabolite treatment on STB infection in planta, with mixed results. These results provide insight into how Z. tritici survives as an epiphyte on the leaf surface and provides a novel avenue for controlling this pathogen indirectly through controlling its interactor bacteria.<p></p>

Author dc:creator

• Nathaniel Strong (21047777)

• Plant Pathology
• Plant Science
• Microbiology
• Mycology
• Microbial Ecology
• Raman Spectroscopy
• Wheat
• Zymoseptoria tritici
• Biofilm

Statement dc:rights

• All rights reserved
• Open Access after 2027-11-16

Identifier

10779/exe.32306682.v1

OAI identifier oai:identifier

oai:figshare.com:article/32306682