Segmented filamentous bacteria are worldwide human gut commensals

Area of Science:

• Microbiology
• Immunology
• Human Microbiome Research

Background:

• Segmented filamentous bacteria (SFB) are known gut commensals in various animals, influencing host immunity and colonization resistance.
• While SFB's role in animal health and disease is established, their presence and characteristics in humans are poorly understood.
• Limited information exists on human SFB, necessitating research into their identification, prevalence, and ecological role.

Purpose of the Study:

• To identify and characterize a novel human SFB species, including its morphology and genomic features.
• To determine the global distribution and diversity of human SFB lineages using bioinformatic approaches.
• To investigate the colonization dynamics and co-colonization potential of human SFB in different age groups.

Main Methods:

• Morphological characterization of a newly identified human SFB species, including electron microscopy for attachment structures.
• Genomic analysis to identify unique features, such as metabolic pathways.
• Bioinformatic analysis of 16S rRNA gene sequences from global human samples to identify SFB lineages.
• Statistical analysis to assess SFB prevalence, distribution, and colonization patterns in relation to age.

Main Results:

• Identification and naming of a new human SFB species, *Anisomitus miae*, common in Africa, possessing unique attachment structures and metabolic genes.
• Bioinformatic identification of six distinct human SFB lineages across 44 countries on all inhabited continents.
• Evidence of SFB co-colonization and a significant colonization peak in children aged one to five years.

Conclusions:

• Multiple SFB species colonize the human gut, representing a widespread, albeit minor, component of the human commensal microbiota.
• Human SFB, particularly *Anisomitus miae*, exhibit specific adaptations for gut colonization and interaction with the host immune system.
• SFB colonization dynamics in humans, especially during early childhood, suggest a significant role in shaping the developing gut microbiome and host immunity.