NMR spectra of Cephalotes ants gut and cuticle

Across the evolutionary history of insects, the shift from nitrogen-rich
carnivore/omnivore diets to nitrogen-poor herbivorous diets was made
possible through symbiosis with microbes. The herbivorous turtle ants
Cephalotes possess a conserved gut microbiome which enriches the nutrient
composition by recycling nitrogen-rich metabolic waste to increase the
production of amino acids. This enrichment is assumed to benefit the host,
but we do not know to what extent. To gain insights into nitrogen
assimilation in the ant cuticle we use gut bacterial manipulation, 15N
isotopic enrichment, isotope-ratio mass spectrometry, and 15N nuclear
magnetic resonance spectroscopy to demonstrate that gut bacteria
contribute to the formation of proteins, catecholamine cross-linkers, and
chitin in the cuticle. This study identifies the cuticular components
which are nitrogen-enriched by gut bacteria highlighting the role of
symbionts in insect evolution and provides a framework for understanding
the nitrogen flow from nutrients through bacteria into the insect cuticle.