Join us at the hyphal frontier

TITLE : At the hyphal frontier: bacterial interactions shape physiology and enniatin production in Fusarium avenaceum

CONTEXT:

Fusarium head blight (FHB) is one of the most damaging fungal diseases of wheat and other cereal crops. Among the species responsible for FHB, Fusarium avenaceum is of particular concern because it produces enniatins (ENNs), emerging mycotoxins frequently detected in cereals and cereal-derived foods. Although the consequences of fungal infection for crop production and food safety are well established, infection is still largely viewed as an interaction between the plant and the pathogen. In reality, the fungus invades tissues that are already occupied by diverse bacterial communities. The expanding mycelium actively reshapes this microbial environment. Through its growth, nutrient consumption and metabolite production, the fungus alters local conditions and may favour certain bacterial populations while limiting others. F. avenaceum may then respond differently to the bacterial partners it encounters: some interactions may facilitate its establishment or development, whereas others may restrict hyphal growth, virulence or secondary metabolism (Chen et al., 2018). These contrasting responses may determine the capacity of the fungus to colonise plant tissues, spread and produce toxins, yet their underlying physiological mechanisms remain largely unknown. ENNs may be central to this process. Beyond their significance as food contaminants, their antibacterial activity varies among bacterial strains and taxa (Roig et al., 2014), suggesting that they may also act as ecological mediators of fungal–bacterial interactions.

OBJECTIVES : The goal of this internship is to provide new insights into the physiological responses of Fusarium avenaceum to interactions with wheat-associated bacteria. The study will particularly focus on how these interactions affect fungal growth, hyphal organisation and ENN production, and on the potential role of ENNs in shaping their outcome.

METHODS : The project will include three steps:

1- Characterisation of the interactions between Fusarium avenaceum and a selected panel of wheat-associated bacterial isolates through coculture assays. Changes in fungal growth and morphology, together with bacterial persistence, will be used to identify promotive, neutral and inhibitory interactions.

2- Physiological characterisation of selected contrasting interactions using fluorescent markers, microscopy and image analysis. These approaches will be used to identify changes in fungal and bacterial physiology resulting from their interaction.

3- Quantification of ENNs in fungal monocultures and cocultures by LC-MS, followed by evaluation of the responses of selected bacterial partners to purified ENNs. 

PREREQUISITES : Background knowledge in microbiology and an interest in fungal physiology and microbial interactions. Experience in microbial culture, microscopy, liquid chromatography, image analysis or data treatment will be appreciated. 

NAME OF THE SUPERVISOR : Joyce Álvarez-Barragán (co-supervision: Louis Carles)

NAME and ADDRESS OF THE TEAM/LABORATORY : INRAE, UR 1264 MycSA - Mycologie et Sécurité des Aliments, 71 avenue Édouard Bourlaux, CS 20032, 33882 Villenave-d'Ornon Cedex, France

TEL : + 33 5 57 12 24 90

E-MAIL : joyce.alvarez-barragan@inrae.fr