Humans and their microbiomes have coevolved as a physiologic community composed of distinct body site niches with metabolic and antigenic diversity. The placental microbiome has not been robustly interrogated, despite recent demonstrations of intracellular bacteria with diverse metabolic and immune regulatory functions. A population-based cohort of placental specimens collected under sterile conditions from 320 subjects with extensive clinical data was established for comparative 16S ribosomal DNA–based and whole-genome shotgun (WGS) metagenomic studies. Identified taxa and their gene carriage patterns were compared to other human body site niches, including the oral, skin, airway (nasal), vaginal, and gut microbiomes from nonpregnant controls. We characterized a unique placental microbiome niche, composed of nonpathogenic commensal microbiota from the Firmicutes, Tenericutes, Proteobacteria, Bacteroidetes, and Fusobacteria phyla. In aggregate, the placental microbiome profiles were most akin (Bray-Curtis dissimilarity <0.3) to the human oral microbiome. 16S-based operational taxonomic unit analyses revealed associations of the placental microbiome with a remote history of antenatal infection (permutational multivariate analysis of variance, P = 0.006), such as urinary tract infection in the first trimester, as well as with preterm birth <37 weeks (P = 0.001).

The social amoebae are exceptional in their ability to alternate between unicellular and multicellular forms. Here we describe the genome of the best-studied member of this group, Dictyostelium discoideum. The gene-dense chromosomes encode ~12,500 predicted proteins, a high proportion of which have long repetitive amino acid tracts. There are many genes for polyketide synthases and ABC transporters, suggesting an extensive secondary metabolism for producing and exporting small molecules. The genome is rich in complex repeats, one class of which is clustered and may serve as centromeres. Partial copies of the extrachromosomal rDNA element are found at the ends of each chromosome, suggesting a novel telomere structure and the use of a common mechanism to maintain both the rDNA and chromosomal termini. A proteome-based phylogeny shows that the amoebozoa diverged from the animal/fungal lineage after the plant/animal split, but Dictyostelium appears to have retained more of the diversity of the ancestral genome than either of these two groups.The amoebozoa are a richly diverse group of organisms whose genomes remain largely unexplored. The soil-dwelling social amoeba Dictyostelium discoideum has been actively studied for the past fifty years and has contributed greatly to our understanding of cellular motility, signalling and interaction 1 . For example, studies in Dictyostelium provided the first descriptions of a eukaryotic cell chemo-attractant and a cell-cell adhesion protein 2, 3 .Dictyostelium amoebae inhabit forest soil consuming bacteria and yeast, which they track by chemotaxis. Starvation, however, prompts the solitary cells to aggregate and to develop as a true multicellular organism, producing a fruiting body comprised of a cellular, cellulosic stalk supporting a bolus of spores. Thus, Dictyostelium has evolved mechanisms that direct the differentiation of a homogeneous population of cells into distinct cell types, regulate the proportions between tissues and orchestrate the construction of an effective structure for the dispersal of spores 4 . Many of the genes necessary for these processes in Dictyostelium were Eichinger et al. Page 2 Nature. Author manuscript; available in PMC 2006 January 27. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript also inherited by metazoa and fashioned through evolution for use within many different modes of development.The amoebozoa are also noteworthy as representing one of the earliest branches from the last common ancestor of all eukaryotes. Each of the surviving branches of the crown group of eukaryotes provides an example of the ways in which the ancestral genome has been sculpted and adapted by lineage-specific gene duplication, divergence and deletion. Comparison between representatives of these branches promises to shed light not only on the nature and content of the ancestral eukaryotic genome, but on the diversity of ways in which its components have been adapted to meet the needs of complex organisms. The genome of Dictyosteliu...

Human microbial communities are characterized by their taxonomic, metagenomic, and metabolic diversity, which varies by distinct body sites and influences human physiology. However, when and how microbial communities within each body niche acquire unique taxonomical and functional signatures in early life remains underexplored. We thus sought to assess the taxonomic composition and potential metabolic function of the neonatal and early infant microbiota across multiple body sites, and assess the impact of mode of delivery and its potential confounders or modifiers. A cohort of pregnant women in their early 3rd trimester (n=81) were prospectively enrolled for longitudinal sampling through 6 weeks post-delivery, and a second matched cross-sectional cohort (n=81) was additionally recruited for sampling once at delivery. Samples were collected for each maternal-infant dyad across multiple body sites, including stool, oral gingiva, nares, skin and vagina. 16S rRNA gene sequencing analysis and whole genome shotgun sequencing was performed to interrogate the composition and function of the neonatal and maternal microbiota. We found that the neonatal microbiota and its associated functional pathways were relatively homogenous across all body sites at delivery, with the notable exception of neonatal meconium. However, by 6 weeks, the infant microbiota structure and function had significantly expanded and diversified, with body site serving as the primary determinant of the bacterial community composition and its functional capacity. Although minor variations in the neonatal (immediately at birth) microbiota community structure were associated with Cesarean delivery in some body sites (oral, nares, and skin; R2 = 0.038), this was not true in neonatal stool (meconium, Mann-Whitney p>0.05) and there was no observable difference in community function regardless of delivery mode. By 6 weeks of age, the infant microbiota structure and function had expanded and diversified with demonstrable body site specificity (p<0.001, R2 = 0.189), and no discernable differences in neither community structure nor function by Cesarean delivery were identifiable (p=0.057, R2 = 0.007). We conclude that within the first 6 weeks of life, the infant microbiota undergoes significant reorganization that is primarily driven by body site and not by mode of delivery.

While current major national research efforts ( i.e., the NIH Human Microbiome Project) will enable comprehensive metagenomic characterization of the adult human microbiota, how and when these diverse microbial communities take up residence in the host and during reproductive life are unexplored at a population level. Because microbial abundance and diversity might differ in pregnancy, we sought to generate comparative metagenomic signatures across gestational age strata. DNA was isolated from the vagina (introitus, posterior fornix, midvagina) and the V5V3 region of bacterial 16S rRNA genes were sequenced (454FLX Titanium platform). Sixty-eight samples from 24 healthy gravidae (18 to 40 confirmed weeks) were compared with 301 non-pregnant controls (60 subjects). Generated sequence data were quality filtered, taxonomically binned, normalized, and organized by phylogeny and into operational taxonomic units (OTU); principal coordinates analysis (PCoA) of the resultant beta diversity measures were used for visualization and analysis in association with sample clinical metadata. Altogether, 1.4 gigabytes of data containing >2.5 million reads (averaging 6,837 sequences/sample of 493 nt in length) were generated for computational analyses. Although gravidae were not excluded by virtue of a posterior fornix pH >4.5 at the time of screening, unique vaginal microbiome signature encompassing several specific OTUs and higher-level clades was nevertheless observed and confirmed using a combination of phylogenetic, non-phylogenetic, supervised, and unsupervised approaches. Both overall diversity and richness were reduced in pregnancy, with dominance of Lactobacillus species (L. iners crispatus , jensenii and johnsonii , and the orders Lactobacillales (and Lactobacillaceae family), Clostridiales, Bacteroidales, and Actinomycetales. This intergroup comparison using rigorous standardized sampling protocols and analytical methodologies provides robust initial evidence that the vaginal microbial 16S rRNA gene catalogue uniquely differs in pregnancy, with variance of taxa across vaginal subsite and gestational age.