Moving beyond microbiome-wide associations to causal microbe identification

Area of Science:

• Microbiology
• Immunology
• Gastroenterology

Background:

• Microbiome-wide association studies link gut microbiota changes to diseases but often lack causal insights.
• Identifying specific microbes responsible for disease pathogenesis remains a challenge.

Purpose of the Study:

• To develop and validate a microbe-phenotype triangulation method for identifying causal microbes.
• To move beyond correlative studies in microbiome research towards establishing causation.

Main Methods:

• Utilized gnotobiotic mice with defined microbial communities in a colitis model.
• Employed co-housing experiments to create hybrid microbiotas and assess intermediate phenotypes.
• Mapped microbe-phenotype relationships across parental and hybrid mouse models.

Main Results:

• Microbe-phenotype triangulation successfully reduced noise and identified causal microbes.
• The bacterial family Lachnospiraceae was associated with protection against colitis.
• Discovered and isolated Clostridium immunis, a novel species conferring protection against colitis.

Conclusions:

• Microbe-phenotype triangulation is an effective strategy for identifying causal microbes from complex microbiota data.
• This approach can identify commensal organisms modulating host phenotypes, such as disease resistance and antimicrobial peptide induction.
• The method holds broad applicability for human microbiome studies to uncover disease-modulating bacteria.