Distinct antimicrobial peptide expression determines host species-specific bacterial associations

I like the language in this article and how it’s framed around looking at microbial community development.  Use of an invertebrate host (hydra) to look at co-evolution of host and microbe populations, with selection of communities based on the types of antimicrobial peptides that are expressed.

Abstract:  

Animals are colonized by co-evolved bacterial communities, which contribute to the host’s health. This commensal microbiota is often highly specific to its host-species, inferring strong selective pressures on the associated microbes. Several factors, including diet, mucus composition, and the immune system have been proposed as putative determinants of host-associated bacterial communities. Here we report that species-specific antimicrobial peptides account for different bacterial communities associated with closely related species of the cnidarian Hydra. Gene family extensions for potent antimicrobial peptides, the arminins, were detected in four Hydra species, with each species possessing a unique composition and expression profile of arminins. For functional analysis, we inoculated arminin-deficient and control polyps with bacterial con- sortia characteristic for different Hydra species and compared their selective preferences by 454 pyrosequencing of the bacterial microbiota. In contrast to control polyps, arminin-deficient polyps displayed decreased potential to select for bacterial communities resembling their native microbiota. This finding indicates that species-specific antimicrobial peptides shape species-specific bacterial associations. 

Significance:  

Animals form functional unities with communities of microbes. Often, these bacterial communities are highly specific to host species and resemble host phylogeny. But which factors determine community membership? Which host-factors are capable of selecting suitable bacteria by inhibiting colonization by potential foreign colonizers? In this study, we show that animals express a species-specific repertoire of antimicrobial peptides, which supports and maintains a species-specific bacterial community. Loss-of-function experiments showed that antimicrobial peptide composition is a predictor for bacterial colonization. 

http://www.pnas.org/content/early/2013/08/28/1304960110.abstract

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