Combined cellular and proteomics approach suggests differential processing of a native and a foreign vibrio in the sponge <i>Halicondria panicea</i>

Metazoans recognize and discriminate between different microbes. In marine invertebrates, the underlying mechanisms of microbial discrimination and immune specificity are, however, not well understood. Phagocytosis is a conserved cellular process from amoeba to humans that facilitates the ingestion and digestion of microbial cells and likely plays a role in this discrimination. To elucidate the molecular and cellular basis of this microbial discrimination, we examined the differential phagocytic processing of a native (i.e., sponge-isolated) and foreign (i.e., sea anemone-isolate) <i>Vibrio</i> in a marine sponge. Our findings revealed that both vibrios provoke an initial bacterial infection- and immune-related, followed by a lysosomal- and endocytic-related proteomic response. Nuanced differences in the cellular and molecular processing suggest a strain-specific discrimination between the two vibrios. This study investigates a mechanism for microbial discrimination in an early-divergent metazoan and may provide a valuable model for studying the evolution of immunity and its role in animal-microbe interactions.