Host lipids regulate multicellular behavior of a predator of a human pathogen

Abstract

ABSTRACTAs symbionts of animals, microbial eukaryotes benefit and harm their hosts in myriad ways. A model microeukaryote (Capsaspora owczarzaki) is a symbiont ofBiomphalaria glabratasnails and may prevent transmission of parasitic schistosomes from snails to humans. However, it is unclear which host factors determineCapsaspora’s ability to colonize snails. Here, we discovered thatCapsasporaforms multicellular aggregates when exposed to snail hemolymph. We identified a molecular cue for aggregation: a hemolymph-derived phosphatidylcholine, which becomes elevated in schistosome-infected snails. Therefore,Capsasporaaggregation may be a response to the physiological state of its host, and it may determine its ability to colonize snails and exclude parasitic schistosomes. Furthermore,Capsasporais an evolutionary model organism whose aggregation may be ancestral to animals. This discovery, that a prevalent lipid inducesCapsasporamulticellularity, suggests that this aggregation phenotype may be ancient. Additionally, the specific lipid will be a useful tool for further aggregation studies.