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Abstract

Associations between animals and microbes affect not only the immediate
tissues where they occur, but also the entire host. Metabolomics, the
study of small biomolecules generated during metabolic processes,
provides a window into how mutualistic interactions shape host
biochemistry. The Hawaiian bobtail squid, Euprymna scolopes, is amenable
to metabolomic studies of symbiosis because the host can be reared with
or without its species-specific symbiont, Vibrio fischeri In addition,
unlike many invertebrates, the host squid has a closed circulatory
system. This feature allows a direct sampling of the refined collection
of metabolites circulating through the body, a focused approach that has
been highly successful with mammals. Here, we show that rearing E.
scolopes without its natural symbiont significantly affected one quarter
of the more than 100 hemolymph metabolites defined by gas chromatography
mass-spectrometry analysis. Further, as in mammals, which harbor complex
consortia of bacterial symbionts, the metabolite signature oscillated on
symbiont-driven daily rhythms and was dependent on the sex of the host.
Thus, our results provide evidence that the population of even a single
symbiont species can influence host hemolymph biochemistry as a function
of symbiotic state, host sex, and circadian rhythm.