A well-balanced human diet includes a significant intake of non-starch polysaccharides, collectively termed “dietary fibre,” from the cell walls of diverse fruits and vegetables.1 Due to a paucity of alimentary enzymes encoded by the human genome,2 our ability to derive energy from dietary fibre depends on saccharification and fermentation of complex carbohydrates by the massive microbial community residing in our distal gut.3,4 The xyloglucans (XyGs), in particular, are a ubiquitous family of highly branched plant cell wall polysaccharides5,6 whose mechanism(s) of degradation in the human gut and consequent importance in nutrition was heretofore unknown.1,7,8 Here, we demonstrate that a single, complex gene locus in Bacteroides ovatus confers xyloglucan catabolism in this common colonic symbiont. Through targeted gene disruption, biochemical analysis of all predicted glycoside hydrolases and carbohydrate-binding proteins, and three-dimensional structural determination of the vanguard endo-xyloglucanase, we reveal the molecular mechanisms through which XyGs are hydrolysed to component monosaccharides for further metabolism. We also observe that orthologous xyloglucan utilization loci (XyGULs) serve as genetic markers of xyloglucan catabolism in Bacteroidetes, that XyGULs are restricted to a limited number of phylogenetically diverse strains, and that XyGULs are ubiquitous in surveyed human metagenomes. Our findings reveal that the metabolism of even highly abundant components of dietary fibre may be mediated by niche species, which has immediate fundamental and practical implications for gut symbiont population ecology in the context of human diet, nutrition and health.9–12

Humans host an intestinal population of microbes—collectively referred to as the gut microbiome—which encode the carbohydrate active enzymes, or CAZymes, that are absent from the human genome. These CAZymes help to extract energy from recalcitrant polysaccharides. The question then arises as to if and how the microbiome adapts to new carbohydrate sources when modern humans change eating habits. Recent metagenome analysis of microbiomes from healthy American, Japanese, and Spanish populations identified putative CAZymes obtained by horizontal gene transfer from marine bacteria, which suggested that human gut bacteria evolved to degrade algal carbohydrates—for example, consumed in form of sushi. We approached this hypothesis by studying such a polysaccharide utilization locus (PUL) obtained by horizontal gene transfer by the gut bacterium Bacteroides plebeius . Transcriptomic and growth experiments revealed that the PUL responds to the polysaccharide porphyran from red algae, enabling growth on this carbohydrate but not related substrates like agarose and carrageenan. The X-ray crystallographic and biochemical analysis of two proteins encoded by this PUL, BACPLE_01689 and BACPLE_01693 , showed that they are β-porphyranases belonging to glycoside hydrolase families 16 and 86, respectively. The product complex of the GH86 at 1.3 Å resolution highlights the molecular details of porphyran hydrolysis by this new porphyranase. Combined, these data establish experimental support for the argument that CAZymes and associated genes obtained from extrinsic microbes add new catabolic functions to the human gut microbiome.

The critical importance of gastrointestinal microbes to digestion of dietary fiber in humans and other mammals has been appreciated for decades. Symbiotic microorganisms expand mammalian digestive physiology by providing an armament of diverse polysaccharide degrading enzymes, which are largely absent in mammalian genomes. By out-sourcing this aspect of digestive physiology to our gut microbes, we maximize our ability to adapt to different carbohydrate nutrients on time scales as short as several hours, due to the ability of the gut microbial community to rapidly alter its physiology from meal-to-meal. Because of their ability to pick up new traits by lateral gene transfer, our gut microbes also enable adaption over time periods as long as centuries and millennia by adjusting their gene content to reflect cultural dietary trends. Despite a vast amount of sequence-based insight into the metabolic potential of gut microbes, the specific mechanisms by which symbiotic gut microorganisms recognize and attack complex carbohydrates remain largely undefined. Here, we review the recent literature on this topic and posit that numerous, subtle variations in polysaccharides diversify the spectrum of available nutrient niches, each of which may be best filled by a subset of microorganisms that possess the corresponding proteins to recognize and degrade different carbohydrates. Understanding these relationships at precise mechanistic levels will be essential to obtain a complete understanding of the forces shaping gut microbial ecology and genomic evolution, as well as devising strategies to intentionally manipulate the composition and physiology of the gut microbial community to improve health.

Utilization of a GnRH-agonist trigger increases the number of MII oocytes and 2PN embryos available for cryopreservation in cancer patients undergoing COS for fertility preservation.

Objectives Intraperitoneal (IP)-based chemotherapy following primary debulking surgery (PDS), although associated with substantial toxicity, is supported by a strong evidence base. We sought to determine feasibility and outcomes of IP chemotherapy after interval debulking surgery (IDS) among patients deemed ineligible for PDS. Methods We identified all patients with high-grade, stage III/IV ovarian cancer treated at our institution with neoadjuvant chemotherapy (NACT) followed by IDS and postoperative chemotherapy from 1/2008–5/2013. IP and intravenous (IV) regimens were defined; demographic and clinical data were analyzed using appropriate statistics. Results Of 128 evaluable patients, 118 (92%) achieved ≤1cm residual disease at IDS and 74 (58%) achieved a complete gross resection (CGR). An IP port was placed in 54/128 patients (42%), with 89% port utilization. Forty-eight (38%) of 128 patients received IP chemotherapy, 17 (13%) weekly IV paclitaxel/q3week carboplatin, and 63 (49%) q3week IV carboplatin/paclitaxel. Patients completed a median of 3 IP cycles (range, 2–6), with 3 (5.5%) of 54 ports removed due to complications. Overall survival (OS) for patients with a CGR treated with IP and weekly IV chemotherapy was 53.2 months (range, 24.7-NE), and 44.2 months (range, 30.2-NE) with any visible residual disease (p<0.001). Median OS was 53.2 months (range, 44.5-NE) for IP-, not reached for weekly IV-, and 34.2 months (range, 27.5–49.8) for q3week IV-treated patients (p=0.1). Conclusions Patients administered IP after IDS had a high rate of successful port utilization, with few regimen switches. Oncologic outcomes were optimal in patients with a CGR at IDS, regardless of chemotherapy used.

Combined GnRH-a and hCG trigger in ICSI cycles increase oocyte maturity, fertilization, clinical pregnancy, and live birth rates in patients with a history of poor fertilization after standard hCG trigger alone.

This survey study uses responses from physicians and medical students to assess psychosocial burdens of family building in the physician workforce.

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