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Abstract BackgroundAnimals form complex symbiotic associations with their gut microbes, whose evolution is determined by an intricate network of host and environmental factors. In many insects, such asDrosophila melanogaster, the microbiome is flexible, environmentally determined, and less diverse than in mammals. In contrast, mammals maintain complex multispecies consortia that are able to colonize and persist in the gastrointestinal tract. Understanding the evolutionary and ecological dynamics of gut microbes in different hosts is challenging. This requires disentangling the ecological factors of selection, determining the timescales over which evolution occurs, and elucidating the architecture of such evolutionary patterns. ResultsWe employ experimental evolution to track the pace of the evolution of a common gut commensal,Lactiplantibacillus plantarum, within invertebrate (Drosophila melanogaster) and vertebrate (Mus musculus) hosts and their respective diets. We show that inDrosophila, the nutritional environment dictates microbial evolution, while the host benefitsL. plantarumgrowth only over short ecological timescales. By contrast, in a mammalian animal model,L. plantarumevolution results to be divergent between the host intestine and its diet, both phenotypically (i.e., host-evolved populations show higher adaptation to the host intestinal environment) and genomically. Here, both the emergence of hypermutators and the high persistence of mutated genes within the host’s environment strongly differed from the low variation observed in the host’s nutritional environment alone. ConclusionsOur results demonstrate thatL. plantarumevolution diverges between insects and mammals. While the symbiosis betweenDrosophilaandL. plantarumis mainly determined by the host diet, in mammals, the host and its intrinsic factors play a critical role in selection and influence both the phenotypic and genomic evolution of its gut microbes, as well as the outcome of their symbiosis.
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This content will become publicly available on December 6, 2025
A conserved bacterial genetic basis for commensal-host specificity
Animals selectively acquire specific symbiotic gut bacteria from their environments that aid host fitness. To colonize, a symbiont must locate its niche and sustain growth within the gut. Adhesins are bacterial cell surface proteins that facilitate attachment to host tissues and are often virulence factors for opportunistic pathogens. However, the attachments are often transient and nonspecific, and additional mechanisms are required to sustain infection. In this work, we use live imaging of individual symbiotic bacterial cells colonizing the gut of livingDrosophila melanogasterto show thatLactiplantibacillus plantarumspecifically recognizes the fruit fly foregut as a distinct physical niche.L. plantarumestablishes stably within its niche through host-specific adhesins encoded by genes carried on a colonization island. The adhesin binding domains are conserved throughout the Lactobacillales, and the island also encodes a secretion system widely conserved among commensal and pathogenic bacteria.
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- PAR ID:
- 10563724
- Publisher / Repository:
- Science
- Date Published:
- Journal Name:
- Science
- Volume:
- 386
- Issue:
- 6726
- ISSN:
- 0036-8075
- Page Range / eLocation ID:
- 1117 to 1122
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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