Human gut bacteria contain acquired interbacterial defence systems

Area of Science:

• Microbiology
• Genomics
• Human Microbiome Research

Background:

• The human gut microbiome's composition is influenced by microbial interactions, not just diet or host immunity.
• Bacteria in the gut possess mechanisms for direct antagonism, including the type VI secretion system (T6SS).
• The T6SS delivers toxic effectors between bacterial cells, impacting community structure.

Purpose of the Study:

• To investigate acquired interbacterial defence (AID) gene clusters in human gut Bacteroidales.
• To understand the role of these clusters in bacterial antagonism and microbiome ecology.
• To characterize the structure and function of a specific subtype, recombinase-associated AID (rAID-1).

Main Methods:

• Bioinformatic analysis to identify AID gene clusters in Bacteroidales genomes.
• In vitro experiments to assess toxin resistance conferred by AID clusters.
• Gnotobiotic mouse models to validate AID function in vivo.
• Structural analysis of rAID-1 gene clusters.

Main Results:

• Discovery of AID gene clusters in human gut Bacteroidales, encoding immunity genes.
• Demonstration that AID clusters confer resistance to T6SS-mediated antagonism.
• Evidence of AID cluster mobility on mobile elements, enabling horizontal gene transfer.
• Identification and validation of the rAID-1 subtype, showing broad distribution and evidence of active gene acquisition.

Conclusions:

• AID systems neutralize bacterial antagonism, playing a key role in shaping the human gut microbiome.
• Mobile AID clusters contribute to bacterial adaptation and survival within the gut environment.
• The findings highlight the importance of interbacterial warfare and defense in microbial ecology.