The type VI secretion system deploys antifungal effectors against microbial competitors

Area of Science:

• Microbiology
• Molecular Biology
• Mycology

Background:

• Bacterial interactions with fungi are crucial in polymicrobial communities.
• Bacteria utilize protein secretion systems, like the type VI secretion system (T6SS), for inter-organismal competition.
• T6SS effectors targeting fungi were previously unreported.

Purpose of the Study:

• To investigate the potential of the bacterial T6SS to target fungal cells.
• To identify novel T6SS effector proteins with antifungal activity.
• To elucidate the mechanisms by which these effectors cause fungal cell death.

Main Methods:

• Utilized Serratia marcescens T6SS for antifungal activity assays.
• Employed 'in competition' proteomics to identify effector proteins.
• Analyzed the impact of effectors on fungal nutrient uptake, metabolism, autophagy, and membrane potential.

Main Results:

• Demonstrated that Serratia marcescens T6SS exhibits antifungal activity against pathogenic Candida species.
• Identified two novel antifungal effectors, Tfe1 and Tfe2, delivered by the T6SS.
• Tfe2 disrupts fungal nutrient uptake and metabolism, inducing autophagy; Tfe1 causes loss of plasma membrane potential.

Conclusions:

• The bacterial T6SS possesses antifungal capabilities, expanding its known functional repertoire.
• Antifungal T6SS effectors like Tfe1 and Tfe2 are significant factors in bacterial-fungal interactions.
• Antifungal T6SSs may be widespread and play a critical role in shaping polymicrobial communities.