The microbiome of the marine flatworm Macrostomum lignano provides fitness advantages and exhibits circadian rhythmicity

The close association between animals and their associated microbiota is usually beneficial for both partners. Here, we used a simple marine model invertebrate, the flatworm Macrostomum lignano, to characterize the host-microbiota interaction in detail. This analysis revealed that the different developmental stages each harbor a specific microbiota. Studies with gnotobiotic animals clarified the physiological significance of the microbiota. While no fitness benefits were mediated by the microbiota when food was freely available, animals with microbiota showed significantly increased fitness with a reduced food supply. The microbiota of M. lignano shows circadian rhythmicity, affecting both the total bacterial load and the behavior of specific taxa. Moreover, the presence of the worm influences the composition of the bacterial consortia in the environment. In summary, the Macrostomum-microbiota system described here can serve as a general model for host-microbe interactions in marine invertebrates. A circadian rhythm and the capacity to manage fitness during limited food availability is identified in the microbiome of the marine flatworm.

Automated summary

The close relationship between animals and their associated microbiota is beneficial for both partners. The flatworm Macrostomum lignano was used as a model to study the host-microbiota interaction in detail. The study found that different developmental stages of the flatworm have specific microbiota and that the microbiota plays a physiological role in the host's fitness, particularly under conditions of limited food supply. The microbiota of M. lignano exhibits a circadian rhythm and influences the behavior of specific bacterial taxa, while the presence of the worm affects the composition of bacterial communities in the environment. Overall, this study provides insights into host-microbe interactions in marine invertebrates using the Macrostomum-microbiota system.