The proportion of the human gut bacterial community that is recalcitrant to culture remains poorly defined. In this report, we combine high-throughput anaerobic culturing techniques with gnotobiotic animal husbandry and metagenomics to show that the human fecal microbiota consists largely of taxa and predicted functions that are represented in its readily cultured members. When transplanted into gnotobiotic mice, complete and cultured communities exhibit similar colonization dynamics, biogeographical distribution, and responses to dietary perturbations. Moreover, gnotobiotic mice can be used to shape these personalized culture collections to enrich for taxa suited to specific diets. We also demonstrate that thousands of isolates from a single donor can be clonally archived and taxonomically mapped in multiwell format to create personalized microbiota collections. Retrieving components of a microbiota that have coexisted in single donors who have physiologic or disease phenotypes of interest and reuniting them in various combinations in gnotobiotic mice should facilitate preclinical studies designed to determine the degree to which tractable bacterial taxa are able to transmit donor traits or influence host biology.gut bacterial diversity | nutrient-microbe interactions | translational medicine pipeline for human microbiome E fforts to dissect the functional interactions between microbial communities and their habitats are complicated by the longstanding observation that, for many of these communities, the great majority of organisms have not been cultured in the laboratory (1). Methodological differences between culture-independent and culture-based approaches have contributed to the challenge of deriving a realistic appreciation of exactly how much discrepancy exists between the culturable components of a microbial ecosystem and total community diversity. Table S1 gives examples of these methodological differences.The largest microbial community in the human body resides in the gut: Its microbiome contains at least two orders of magnitude more genes than are found in our Homo sapiens genome (2). Culture-independent metagenomic studies of the human gut microbiota are identifying microbial taxa and genes correlated with host phenotypes, but mechanistic and experimentally demonstrated links between key community members and specific aspects of host biology are difficult to establish with these methods alone. The goals of the present study were (i) to evaluate the representation of readily cultured phylotypes in the human gut microbiota; (ii) to profile the dynamics of these cultured communities in a mammalian gut ecosystem; and (iii) to determine whether a clonally arrayed, personalized strain collection could be constructed to serve as a foundation for reassembling varying elements of a human's gut microbiota in vitro or in vivo. ResultsTo estimate the abundance of readily cultured bacterial phylotypes in the distal human gut, primers were used to amplify variable region 2 (V2) of bacterial 16S ribosomal RNA (rRN...

In eukaryotic cells, nuclear export of nascent ribosomal subunits through the nuclear pore complex depends on the small GTPase Ran. However, neither the nuclear export signals (NESs) for the ribosomal subunits nor the receptor proteins, which recognize the NESs and mediate export of the subunits, have been identified. We showed previously that Nmd3p is an essential protein from yeast that is required for a late step in biogenesis of the large (60S) ribosomal subunit. Here, we show that Nmd3p shuttles and that deletion of the NES from Nmd3p leads to nuclear accumulation of the mutant protein, inhibition of the 60S subunit biogenesis, and inhibition of the nuclear export of 60S subunits. Moreover, the 60S subunits that accumulate in the nucleus can be coimmunoprecipitated with the NES-deficient Nmd3p. 60S subunit biogenesis and export of truncated Nmd3p were restored by the addition of an exogenous NES. To identify the export receptor for Nmd3p we show that Nmd3p shuttling and 60S export is blocked by the Crm1p-specific inhibitor leptomycin B. These results identify Crm1p as the receptor for Nmd3p export. Thus, export of the 60S subunit is mediated by the adapter protein Nmd3p in a Crm1p-dependent pathway.

The matrix protein VP40 plays a critical role in Ebola virus assembly and budding, a process that utilizes specialized membrane domains known as lipid rafts. Previous studies with purified protein suggest a role for oligomerization of VP40 in this process. Here, we demonstrate VP40 oligomers in lipid rafts of mammalian cells, virus-like particles, and in the authentic Ebola virus. By mutagenesis, we identify several critical C-terminal sequences that regulate oligomerization at the plasma membrane, association with detergent-resistant membranes, and vesicular release of VP40, directly linking these phenomena. Furthermore, we demonstrate the active recruitment of TSG101 into lipid rafts by VP40. We also report the successful application of the biarsenic fluorophore, FlAsH, combined with a tetracysteine tag for imaging of Ebola VP40 in live cells.rafts ͉ FlAsH ͉ TSG101 ͉ filovirus