ena-STUDY-EBI-UI-29-10-2013-14:28:51:778-53
This study utilizes a metagenome-based approach to elucidate the phylogenetic and functional gene diversity of fecal microbiome in Galapagos land and marine iguanas.
While much has been known about the fecal microbiome of mammalian herbivorous, little is known about the fecal microbiome of reptilian herbivores. To elucidate the functional gene diversity of reptilian herbivores, we performed a metagenome-based analysis of the fecal samples from the algae-consuming marine iguana (Amblyrhynchus cristatus) and terrestrial flora-consuming land iguanas (genus Conolophus) that are indigenous on the Galápagos Archipelago. Further comparison was made against the mammalian herbivorous hosts, and our findings suggested that the phylogenetic affiliations of both land iguanas (LI) and marine iguanas (MI) fecal microbiota clustered apart, and shared low similarity with the mammalian herbivorous hosts. Furthermore, functional gene diversities in both iguana hosts showed differentiation based on the diet, in which the MI fecal microbiota had a functional diversity that clustered apart from the other terrestrial-flora consuming LI iguana and herbivorous mammalian hosts. The differentiation in the functional gene diversity of MI fecal microbiota is likely attributed to a distinctly unique diet that is based on marine algae. A further examination of the carbohydrate-degrading genes revealed that several of the prevalent glycosyl hydrolases (GH), glycosyl transferases (GT), carbohydrate binding modules (CBM) and carbohydrate esterases (CE) gene classes were conserved among all examined herbivorous mammalian and reptilian hosts, reiterating the important roles these genes have in the breakdown and metabolism of herbivorous diet. However, some classes of carbohydrates-degrading families like GH2, GH13, GT2, GT4, CBM50, CBM48, CE4 and CE11, as well as genes associated with sulfur metabolism and dehalogenation were highly expressed or unique to the MI fecal microbiota. In contrast, gene sequences that relate to archaeal methanogenesis were detected only in LI fecal microbiome, and carbohydrate-degrading families like GH13, GH66, GT2, GT4, CBM50, CBM13, CE4 and CE8 were highly abundant in the LI. Certain bacterial populations were enriched over ten generations in various substrates (e.g. glucose, arabinose, xylose), and the enriched populations exhibited differences based on the iguana host and the type of enrichment substrate. Majority of the enriched bacterial populations belong to genera Clostridium spp. and Enterococcus spp. that likely accounted for the high prevalence of GH13 and GH2, as well as the GT families (e.g. GT2, GT4, GT28, GT35 and GT51) that were ubiquitously present in the fecal microbiota of all herbivorous hosts.
While much has been known about the fecal microbiome of mammalian herbivorous, little is known about the fecal microbiome of reptilian herbivores. To elucidate the functional gene diversity of reptilian herbivores, we performed a metagenome-based analysis of the fecal samples from the algae-consuming marine iguana (Amblyrhynchus cristatus) and terrestrial flora-consuming land iguanas (genus Conolophus) that are indigenous on the Galápagos Archipelago. Further comparison was made against the mammalian herbivorous hosts, and our findings suggested that the phylogenetic affiliations of both land iguanas (LI) and marine iguanas (MI) fecal microbiota clustered apart, and shared low similarity with the mammalian herbivorous hosts. Furthermore, functional gene diversities in both iguana hosts showed differentiation based on the diet, in which the MI fecal microbiota had a functional diversity that clustered apart from the other terrestrial-flora consuming LI iguana and herbivorous mammalian hosts. The differentiation in the functional gene diversity of MI fecal microbiota is likely attributed to a distinctly unique diet that is based on marine algae. A further examination of the carbohydrate-degrading genes revealed that several of the prevalent glycosyl hydrolases (GH), glycosyl transferases (GT), carbohydrate binding modules (CBM) and carbohydrate esterases (CE) gene classes were conserved among all examined herbivorous mammalian and reptilian hosts, reiterating the important roles these genes have in the breakdown and metabolism of herbivorous diet. However, some classes of carbohydrates-degrading families like GH2, GH13, GT2, GT4, CBM50, CBM48, CE4 and CE11, as well as genes associated with sulfur metabolism and dehalogenation were highly expressed or unique to the MI fecal microbiota. In contrast, gene sequences that relate to archaeal methanogenesis were detected only in LI fecal microbiome, and carbohydrate-degrading families like GH13, GH66, GT2, GT4, CBM50, CBM13, CE4 and CE8 were highly abundant in the LI. Certain bacterial populations were enriched over ten generations in various substrates (e.g. glucose, arabinose, xylose), and the enriched populations exhibited differences based on the iguana host and the type of enrichment substrate. Majority of the enriched bacterial populations belong to genera Clostridium spp. and Enterococcus spp. that likely accounted for the high prevalence of GH13 and GH2, as well as the GT families (e.g. GT2, GT4, GT28, GT35 and GT51) that were ubiquitously present in the fecal microbiota of all herbivorous hosts.