Intestinal fungi are causally implicated in microbiome assembly and immune development in mice

Area of Science:

• Microbiology and Immunology
• Gut Microbiome Research

Background:

• The gut microbiome comprises bacteria, fungi, and other microorganisms.
• The established role of bacteria in host physiology contrasts with the undetermined role of fungi.
• Understanding fungal contributions is crucial for a complete view of microbiome function.

Purpose of the Study:

• To investigate the causal role of fungi in microbiome assembly.
• To assess fungal impact on immune development, colitis susceptibility, and airway inflammation.
• To explore the interplay between bacteria and fungi in host responses.

Main Methods:

• Germ-free mice were colonized with defined bacterial and/or fungal species.
• Microbiome composition, immune cell development, and inflammatory responses were analyzed.
• Models of dextran sulfate sodium-induced colitis and ovalbumin-induced airway inflammation were used.

Main Results:

• Fungal colonization induced significant shifts in bacterial microbiome ecology.
• Fungi independently influenced innate and adaptive immune development in young mice.
• Co-colonization with bacteria and fungi increased colonic inflammation compared to fungi alone.
• Bacterial colonization, not fungal, was necessary to reduce airway inflammation, though fungi increased airway macrophage infiltration.

Conclusions:

• Fungi play a causal role in shaping microbial ecology and host immune responses.
• The findings support the inclusion of fungi in therapeutic strategies for early-life microbiome modulation.
• This research underscores the importance of a multi-kingdom approach to microbiome studies.