Distinct antimicrobial peptide expression determines host species-specific bacterial associations

Area of Science:

• Microbiology
• Immunology
• Evolutionary Biology

Background:

• Animals host coevolved bacterial communities crucial for health.
• Host-associated microbiota are often species-specific, influenced by factors like diet and immunity.
• Antimicrobial peptides are key components of innate immunity.

Purpose of the Study:

• To investigate the role of species-specific antimicrobial peptides in shaping host-associated bacterial communities in the cnidarian Hydra.
• To determine if antimicrobial peptides, specifically arminins, are responsible for the distinct microbiota observed in closely related Hydra species.

Main Methods:

• Comparative analysis of arminin gene families across four Hydra species.
• Functional experiments involving inoculation of arminin-deficient and control Hydra polyps with bacterial consortia.
• 454 pyrosequencing to analyze bacterial microbiota composition and selective preferences.

Main Results:

• Unique arminin composition and expression profiles were identified in each of the four studied Hydra species.
• Arminin-deficient Hydra polyps exhibited a diminished capacity to select for their characteristic native bacterial communities compared to control polyps.
• This suggests a direct role for arminins in mediating species-specific bacterial associations.

Conclusions:

• Species-specific antimicrobial peptides, particularly arminins, are significant drivers of host-associated bacterial community structure in Hydra.
• Antimicrobial peptides contribute to the specificity of the host-microbe relationship, influencing which bacteria colonize a particular host species.
• The findings highlight the role of innate immunity in shaping symbiotic microbial communities.