Notably, biotin absorption by epithelia takes place in the intestine, suggesting that the residing microbes may significantly contribute to the human biotin supply (Said, 2009). Figure 2 http://www.selleckchem.com/products/baricitinib-ly3009104.html KEGG modules plotted at the metabolic pathways. Pathways that are overrepresented in small intestine versus colon are indicated in blue; pathways that are overrepresented in metatranscriptome versus metagenome are indicated in yellow; overrepresented … Figure 3 Phylogenetic representation of the reads. The size of the bullets represents the relative abundance of the reads per phylogenetic position. Highly abundant phylogenetic groups are indicated. (a) Representation of GS-FLX reads that showed hits to genes …

Remarkably, Cluster of Orthologous Groups (COG) analysis also indicated enrichment of several (pro-)phages (Supplementary Table S4), which is intriguing in the light of the presence of phage-related sequences in the minimal gut metagenome (Qin et al., 2010), in combination with the recently proposed role of phages in sustaining microbial diversity via the ��killing-the-winner’ principle (Rodriguez-Valera et al., 2009). However, these suggestions appear to be contradicted by a recent report, which concludes that large intestinal phages could not be correlated to a diversity-sustaining role (Reyes et al., 2010). Consequently, the importance of phages in sustaining microbial diversity within the small intestinal microbiota remains speculative. pH and metabolite profiles confirm the genetic potential of the microbiota To determine if the genetic potential within the metagenomes is reflected in their activity, pH and metabolites were determined in the respective effluent samples.

The pH in the morning sample (1M) was more than 1 unit lower than the afternoon sample (1A), which reflects the high nutrient availability fluctuations and cognate microbial activity in the small intestine (Table 1). Considerable concentrations of acetate, lactate and butyrate, and sometimes formate, were detected (Table 1), confirming the activity of fermenting bacteria in the small intestine. Concentrations of acetate and butyrate in the small intestine are similar to those observed in fecal samples, whereas propionate concentrations are 3�C5 times lower (Schwiertz et al., 2010). The high concentrations of lactate and butyrate are in agreement with the presence of Streptococcus sp.

and Clostridium cluster XIVa sp., respectively. Genes assigned to the butyrate fermentation pathway were frequently detected in the small intestinal GSK-3 metagenome, but were not enriched compared with colon metagenomes, which agrees with the dominance of butyrate producers in the latter niche (Pryde et al., 2002). Notably, the lactate concentration in sample A was much lower than samples 1A and 1M, whereas acetate levels were higher.