Osmolality as a novel mechanism explaining diet effects on the outcome of infection with a blood parasite

Wilson, Kenneth and Holdbrook, Robert and Reavey, Catherine and Randall, Joanna and Tummala Munuswamy, Yamini and Ponton, Fleur and Simpson, Stephen J. and Smith, Judith and Cotter, Sheena (2020) Osmolality as a novel mechanism explaining diet effects on the outcome of infection with a blood parasite. Current Biology, 30 (13). pp. 2459-2467. ISSN 0960-9822

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Abstract

Recent research has suggested that the outcome of host-parasite interactions is dependent on the diet of the host, but most previous studies have focussed on ‘top down’ mechanisms i.e. how the host’s diet improves the host immune response to drive down the parasite population and improve host fitness. In contrast, the direct impacts of host nutrition on parasite fitness or the mechanisms underpinning these effects are relatively unexplored. Here, using a model host-pathogen system (Spodoptera littoralis caterpillars and Xenorhabdus nematophila, an extracellular bacterial blood parasite), we explore the effects of host dietary macronutrient balance on pathogen growth rates both in vivo and in vitro, allowing us to compare pathogen growth rates both in the presence and absence of the host immune response. In vivo, high dietary protein resulted in lower rates of bacterial establishment, slower bacterial growth, higher host survival and slower speed of host death; in contrast, the energy content and amount of carbohydrate in the diet explained little variation in any measure of pathogen or host fitness. In vitro, we show that these effects are largely driven by the impact of host dietary protein on host hemolymph (blood) osmolality (i.e. its concentration of solutes), with bacterial growth being slower in protein-rich, high osmolality, hemolymphs, highlighting a novel ‘bottom up’ mechanism by which host diet can impact both pathogen and host fitness.

Item Type:
Journal Article
Journal or Publication Title:
Current Biology
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/1300
Subjects:
ID Code:
143525
Deposited By:
Deposited On:
24 Apr 2020 13:20
Refereed?:
Yes
Published?:
Published
Last Modified:
30 Sep 2020 03:06