Human intestinal microbiota plays a number of important roles in human health and is also implicated in several gastrointestinal disorders. Though the diversity of human gut microbiota in adults and in young children has been examined, few reports of microbiota composition are available for adolescents. In this work we used Microbiota Array for high-throughput analysis of distal gut microbiota in adolescent children 11-18 years of age. Samples obtained from healthy adults were used for comparison. Adolescent and adult groups could be separated in principal components analysis space based on the relative species abundance of their distal gut microbiota. All samples were dominated by class Clostridia. A core microbiome of 46 species that were detected in all examined samples was established; members of genera Ruminococcus, Faecalibacterium, and Roseburia were well presented among core species. Comparison of intestinal microbiota composition between adolescents and adults revealed a statistically significantly higher abundance of genera Bifidobacterium and Clostridium among adolescent samples. The number of detected species was similar between sample groups indicating that it was relative abundances of the genera and not the presence or absence of a specific genus that differentiated adolescent and adult samples. In summary, contrary to the current belief, this study suggests that the gut microbiome of adolescent children is different from that of adults.

Although at the higher taxonomical level gut microbiota was similar between healthy and IBS-D children, specific differences in the abundances of several bacterial genera were revealed. Core microbiome in children was dominated by Clostridia. Putative relationships identified among microbial genera provide testable hypotheses of cross-species associations among members of human gut microbiota

While a substantial amount of dietary fats escape absorption in the human small intestine and reach the colon, the ability of resident microbiota to utilize these dietary fats for growth has not been investigated in detail. In this study we used an multi-vessel simulator system of the human colon to reveal that human gut microbiota is able to utilize typically consumed dietary fatty acids to sustain growth. Gut microbiota adapted quickly to a macronutrient switch from a balanced Western diet type medium to its variant lacking carbohydrates and proteins. We defined specific genera that increased their abundance on the fats-only medium, including, , and several genera of class Gammaproteobacteria. In contrast, abundances of well-known glycan and protein degraders including, , and were reduced in such conditions. Predicted prevalences of microbial genes coding for fatty acid degradation enzymes and anaerobic respiratory reductases were significantly increased in the fats-only environment, whereas the abundance of glycan degradation genes was diminished. These changes also resulted in lower microbial production of short chain fatty acids and antioxidants. Our findings provide justification for the previously observed alterations in gut microbiota observed in human and animal studies of high-fat diets. Increased intake of fats in many developed countries raised awareness of potentially harmful and beneficial effects of high fat consumption on human health. Some dietary fats escape digestion in the small intestine and reach the colon where they can be metabolized by gut microbiota. We show that human gut microbes are able to maintain a complex community when supplied with dietary fatty acids as the only nutrient and carbon sources. Such fatty acid based growth leads to lower production of short chain fatty acids and antioxidants by community members, which might potentially have negative health consequences on the host.

Phylogenetic microarrays present an attractive strategy to high-throughput interrogation of complex microbial communities. In this work we present several approaches to optimize the analysis of intestinal microbiota with the recently developed Microbiota Array. First, we determined how 16S rDNA-specific PCR amplification influenced bacterial detection and the consistency of measured abundance values. Bacterial detection improved with an increase in the number of PCR amplification cycles, but 25 cycles were sufficient to achieve the maximum possible detection. A PCR-caused deviation in the measured abundance values was also observed. We also developed two mathematical algorithms aimed to account for a predicted cross-hybridization of 16S rDNA fragments among different species, and to adjust the measured hybridization signal based on the number of 16S rRNA gene copies per species genome. The 16S rRNA gene copy adjustment indicated that the presence of members of class Clostridia might be over-estimated in some 16S rDNA-based studies. Finally, we show that the examination of total community RNA with phylogenetic microarray can provide estimates of the relative metabolic activity of individual community members. Complementary profiling of genomic DNA and total RNA isolated from the same sample presents an opportunity to assess population structure and activity in the same microbial community.

h uman gastrointestinal microbial communities are recognized as important determinants of the host health and disease status. we have recently examined the distal gut microbiota of two groups of children: healthy adolescents and those diagnosed with diarrhea-predominant irritable bowel syndrome (ibs). we have revealed the common core of phylotypes shared among all children, identified genera differentially abundant between two groups and surveyed possible relationships among intestinal microbial genera and phylotypes. in this article we explored the use of supervised and unsupervised ordination and classification methods to separate and classify child fecal samples based on their quantitative microbial profile. we observed sample separation according to the participant health status, and this separation could often be attributed to the abundance levels of several specific microbial genera. we also extended our original correlation network analysis of the relative abundances of bacterial genera across samples and determined possible association networks separately for healthy and ibs groups. interestingly, the number of significant genus abundance associations was drastically lower among the ibs samples, which can potentially be attributed to the existence of multiple routes to microbiota disbalance in ibs or to the loss of microbial interactions during ibs development. IntroductionThe human gut is rich in microbes, harboring approximately 100 trillion do gut microbial communities differ in pediatric ibs and health? Microbes participate in carbohydrate degradation, modulation of dietary lipid uptake, production of certain vitamins and short-chain fatty acids, development and proper stimulation of the immune system, modulation of gut motility and protection of the host from pathogens.3 At the same time, microbiota dysbiosis has been linked to a number of human disorders including irritable bowel syndrome (IBS), inflammatory bowel disease, obesity and colon cancer.3 Among these, IBS is a functional bowel syndrome that has varied symptoms with no sign of visible mucosal damage or intestinal inflammation. Proposed causes of IBS include altered motor function, abnormal gas handling, acute bacterial gastroenteritis, food intolerance, increased intestinal permeability and gut motility, altered intestinal immune function, as well as bacterial overgrowth of small intestine (SIBO). 4,5 While none of the potential causes has yet emerged as the established determinant of IBS development, many of the symptoms of IBS are consistent with SIBO,6 and the prevalence of SIBO was found to be higher in many previous investigations of IBS patients. [7][8][9] While the SIBO model of IBS development implicates intestinal microbiota as a major cause of this syndrome, the available studies of gut microbiota in IBS do not show a strong consensus as to which microbiota members might be responsible for the condition and whether specific ©2013 Landes Bioscience. Do not distribute 348Gut Microbes Volume 4 Issue 4Bacteroides, Clostridium, Dorea...