A distinct class of conjugative megaplasmids includes potential vehicles for prophage dissemination

Area of Science:

• Microbiology
• Genetics
• Genomics

Background:

• Closely related prophages are found in diverse human gut bacteria, but the dissemination mechanism is unclear.
• Limited evidence exists for productive phage infections across broad bacterial host ranges.

Purpose of the Study:

• To identify a mechanism for the widespread distribution of prophages in the human gut microbiome.
• To investigate the role of mobile genetic elements in prophage dissemination.

Main Methods:

• Description of two novel conjugative megaplasmid groups (Hodors) in the human gut microbiome.
• Analysis of Hodor genetic content, including prophage genomes and surface-associated genes.
• Detection of Hodor-associated prophages as extracellular particles and assessment of their transcriptional activity.

Main Results:

• Two distinct, deeply diverged conjugative megaplasmid groups, termed Hodors, were identified.
• Hodors harbor complete prophage genomes and are found across distant Bacillota lineages (Bacilli and Clostridia).
• Hodor-associated prophages can be extracellular and are transcriptionally active.

Conclusions:

• Conjugative megaplasmids (Hodors) act as mobile platforms for prophage dissemination.
• This mechanism explains the widespread occurrence of related prophages in phylogenetically distant gut bacteria.
• Prophage dissemination via Hodors decouples lysogenic host range from infective host range.