Herbivorous reptiles depend on complex gut microbial communities to effectively degrade dietary polysaccharides. The composition of these fermentative communities may vary based on dietary differences. To explore the role of diet in shaping gut microbial communities, we evaluated the fecal samples from two related host species—the algae-consuming marine iguana (Amblyrhynchus cristatus) and land iguanas (LI) (genus Conolophus) that consume terrestrial vegetation. Marine and LI fecal samples were collected from different islands in the Galápagos archipelago. High-throughput 16S rRNA-based pyrosequencing was used to provide a comparative analysis of fecal microbial diversity. At the phylum level, the fecal microbial community in iguanas was predominated by Firmicutes (69.5±7.9%) and Bacteroidetes (6.2±2.8%), as well as unclassified Bacteria (20.6±8.6%), suggesting that a large portion of iguana fecal microbiota is novel and could be involved in currently unknown functions. Host species differed in the abundance of specific bacterial groups. Bacteroides spp., Lachnospiraceae and Clostridiaceae were significantly more abundant in the marine iguanas (MI) (P-value>1E−9). In contrast, Ruminococcaceae were present at >5-fold higher abundance in the LI than MI (P-value>6E−14). Archaea were only detected in the LI. The number of operational taxonomic units (OTUs) in the LI (356–896 OTUs) was >2-fold higher than in the MI (112–567 OTUs), and this increase in OTU diversity could be related to the complexity of the resident bacterial population and their gene repertoire required to breakdown the recalcitrant polysaccharides prevalent in terrestrial plants. Our findings suggest that dietary differences contribute to gut microbial community differentiation in herbivorous lizards. Most importantly, this study provides a better understanding of the microbial diversity in the iguana gut; therefore facilitating future efforts to discover novel bacterial-associated enzymes that can effectively breakdown a wide variety of complex polysaccharides.

The applicability of 454 pyrosequencing to characterize bacterial biofilm communities from two water meters of a drinking water distribution system was assessed. Differences in bacterial diversity and composition were observed. A better understanding of the bacterial ecology of drinking water biofilms will allow for effective management of water quality in distribution systems.

Significance: Fermentation of dietary fiber in the lower gut of humans is a critical process for the function and integrity of both the bacterial community and host cells. Here we demonstrate that two human gut commensal Bacteroides are equipped with unique enzymes that allow degradation of xylan, a common hemicellulose in human diets. Furthermore, we identify a novel carbohydrate-binding module (CBM) family that disrupts the catalytic domain of a glycoside hydrolase 10 (GH10) endoxylanase and facilitates the hydrolytic activity of the enzyme. The conservation of the unique modular architecture of the GH10 endoxylanase in the genomes of diverse Bacteroidetes suggests a critical role in fiber digestion in this phylum.