| The microbial communities that reside within the intestinal tract in vertebrates are complex. However, little is known about how microorganisms establish and maintain a presence in the intestinal ecosystem. How do they interact with their host and with other microbial community members? In which regions of the intestine is colonization preferred? The development of simplified invertebrate model systems offers the opportunity to understand the basic mechanisms underlying the interactions between intestinal microorganisms and their host.;Caenorhabditis elegans possesses key attributes that can make it a model organism for addressing such questions. The genetically tractability of C. elegans has aided study of biological processes including aging, microbial pathogenesis, and innate immunity. As a model for commensalism, we sought to characterize bacterial colonization within the gut of C. elegans. We found that as adult worms age, their capacity to control intestinal bacterial proliferation diminished. Furthermore, we showed that intestinal bacterial proliferation controlled by gut immunity strongly correlated with longevity, suggesting that intestinal bacterial load may be used as a marker to predict lifespan. We also demonstrate that some bacterial species colonizing the intestine are more resilient than others to change. We provide evidence of active competition for colonization niches in the C. elegans intestine and for in vivo bacterial adaptation. Finally, we show that C. elegans can be used as a model system to study bacterial horizontal gene transfer, and to identify host signals modulating bacterial genetic diversity. |
