Genomic diversification of giant enteric symbionts reflects host dietary lifestyles

Herbivorous surgeonfishes are an ecologically successful group of reef fish that rely on marine algae as their principal food source. Here, we elucidated the significance of giant enteric symbionts colonizing these fishes regarding their roles in the digestive processes of hosts feeding predominantly on polysiphonous red algae and brown Turbinaria algae, which contain different polysaccharide constituents. Using metagenomics, single-cell genomics, and metatranscriptomic analyses, we provide evidence of metabolic diversification of enteric microbiota involved in the degradation of algal biomass in these fishes. The enteric microbiota is also phylogenetically and functionally simple relative to the complex lignocellulose-degrading microbiota of terrestrial herbivores. Over 90% of the enzymes for deconstructing algal polysaccharides emanate from members of a single bacterial lineage,

Citation

Ngugi DK, Miyake S, Cahill M, Vinu M, Hackmann TJ, et al. (2017) Genomic diversification of giant enteric symbionts reflects host dietary lifestyles. Proceedings of the National Academy of Sciences 114: E7592–E7601. Available: http://dx.doi.org/10.1073/pnas.1703070114.

Sponsors

We thank the King Abdullah University of Science and Technology (KAUST) Bioscience Core Lab, the Coastal and Marine Resources Core Lab, and T. Sinclair-Taylor for their technical and logistical support. We also thank John Howard Choat (James Cook University, Queensland) for his insights on surgeonfish nutrition, Andreas Brune (Max Planck Institute for Terrestrial Microbiology, Marburg) for assistance with bacterial nomenclature, and Calder J. Atta (KAUST) for the fish illustrations. This work was supported by KAUST through the Saudi Economic and Development Company Research Excellence Award Program (U.S.).