Structure of the germline genome of Tetrahymena thermophila and relationship to the massively rearranged somatic genome

The germline genome of the binucleated ciliate Tetrahymena thermophila undergoes programmed chromosome breakage and massive DNA elimination to generate the somatic genome. Here, we present a complete sequence assembly of the germline genome and analyze multiple features of its structure and its relationship to the somatic genome, shedding light on the mechanisms of genome rearrangement as well as the evolutionary history of this remarkable germline/soma differentiation. Our results strengthen the notion that a complex, dynamic, and ongoing interplay between mobile DNA elements and the host genome have shaped Tetrahymena chromosome structure, locally and globally. Non-standard outcomes of rearrangement events, including the generation of short-lived somatic chromosomes and excision of DNA interrupting protein-coding regions, may represent novel forms of developmental gene regulation. We also compare Tetrahymenas germline/soma differentiation to that of other characterized ciliates, illustrating the wide diversity of adaptations that have occurred within this phylum.</p

Whole Genome Deep Sequencing of HIV-1 Reveals the Impact of Early Minor Variants Upon Immune Recognition During Acute Infection

Deep sequencing technologies have the potential to transform the study of highly variable viral pathogens by providing a rapid and cost-effective approach to sensitively characterize rapidly evolving viral quasispecies. Here, we report on a high-throughput whole HIV-1 genome deep sequencing platform that combines 454 pyrosequencing with novel assembly and variant detection algorithms. In one subject we combined these genetic data with detailed immunological analyses to comprehensively evaluate viral evolution and immune escape during the acute phase of HIV-1 infection. The majority of early, low frequency mutations represented viral adaptation to host CD8+ T cell responses, evidence of strong immune selection pressure occurring during the early decline from peak viremia. CD8+ T cell responses capable of recognizing these low frequency escape variants coincided with the selection and evolution of more effective secondary HLA-anchor escape mutations. Frequent, and in some cases rapid, reversion of transmitted mutations was also observed across the viral genome. When located within restricted CD8 epitopes these low frequency reverting mutations were sufficient to prime de novo responses to these epitopes, again illustrating the capacity of the immune response to recognize and respond to low frequency variants. More importantly, rapid viral escape from the most immunodominant CD8+ T cell responses coincided with plateauing of the initial viral load decline in this subject, suggestive of a potential link between maintenance of effective, dominant CD8 responses and the degree of early viremia reduction. We conclude that the early control of HIV-1 replication by immunodominant CD8+ T cell responses may be substantially influenced by rapid, low frequency viral adaptations not detected by conventional sequencing approaches, which warrants further investigation. These data support the critical need for vaccine-induced CD8+ T cell responses to target more highly constrained regions of the virus in order to ensure the maintenance of immunodominant CD8 responses and the sustained decline of early viremia

Multi-institute analysis of carbapenem resistance reveals remarkable diversity, unexplained mechanisms, and limited clonal outbreaks

Lamp post in the shape of a rostral column, in front of the Hôtel de la Marine; The commission for the Place Louis XV was awarded to the Premier Architecte, Anges-Jacques Gabriel. A preliminary design was approved in 1755; the definitive plan in 1757. Construction of the Place Louis XV continued until the 1770s. Under the direction of Nicolas-Marie Potain, Gabriel’s scheme transformed the muddy Esplanade into a knuckle that reinforced the great east–west axis of the Louvre and the Champs-Elysées, subsequently extended to Neuilly, and linked it with the peripheral boulevards, the Cours de la Reine and, via a bridge built by Perronet in 1786, the Left Bank . The Place Louis XV acted as a catalyst for residential development along the north side of the Champs-Elysées. The Comte de Rambuteau levelled and widened the line of boulevards from the Bastille to the re-named Place de la Concorde (ca. 1840), also redesigned by Hittorff (1829-1854). Source: Grove Art Online; http://www.oxfordartonline.com/ (accessed 7/15/2010

Evolution of extensively drug-resistant tuberculosis over four decades revealed by whole genome sequencing of Mycobacterium tuberculosis from KwaZulu-Natal, South Africa

The largest global outbreak of extensively drug-resistant (XDR) tuberculosis (TB) was identified in Tugela Ferry, KwaZulu-Natal (KZN), South Africa in 2005. The antecedents and timing of the emergence of drug resistance in this fatal epidemic XDR outbreak are unknown, and it is unclear whether drug resistance in this region continues to be driven by clonal spread or by the development of de novo resistance. A whole genome sequencing and drug susceptibility testing (DST) was performed on 337 clinical isolates of Mycobacterium tuberculosis (M.tb) collected in KZN from 2008 to 2013, in addition to three historical isolates, one of which was isolated during the Tugela Ferry outbreak. Using a variety of whole genome comparative approaches, 11 drug-resistant clones of M.tb circulating from 2008 to 2013 were identified, including a 50-member clone of XDR M.tb that was highly related to the Tugela Ferry XDR outbreak strain. It was calculated that the evolutionary trajectory from first-line drug resistance to XDR in this clone spanned more than four decades and began at the start of the antibiotic era. It was also observed that frequent de novo evolution of MDR and XDR was present, with 56 and 9 independent evolutions, respectively. Thus, ongoing amplification of drug-resistance in KwaZulu-Natal is driven by both clonal spread and de novo acquisition of resistance. In drug-resistant TB, isoniazid resistance was overwhelmingly the initial resistance mutation to be acquired, which would not be detected by current rapid molecular diagnostics that assess only rifampicin resistance

Inter-species geographic signatures for tracing horizontal gene transfer and long-term persistence of carbapenem resistance.

BackgroundCarbapenem-resistant Enterobacterales (CRE) are an urgent global health threat. Inferring the dynamics of local CRE dissemination is currently limited by our inability to confidently trace the spread of resistance determinants to unrelated bacterial hosts. Whole-genome sequence comparison is useful for identifying CRE clonal transmission and outbreaks, but high-frequency horizontal gene transfer (HGT) of carbapenem resistance genes and subsequent genome rearrangement complicate tracing the local persistence and mobilization of these genes across organisms.MethodsTo overcome this limitation, we developed a new approach to identify recent HGT of large, near-identical plasmid segments across species boundaries, which also allowed us to overcome technical challenges with genome assembly. We applied this to complete and near-complete genome assemblies to examine the local spread of CRE in a systematic, prospective collection of all CRE, as well as time- and species-matched carbapenem-susceptible Enterobacterales, isolated from patients from four US hospitals over nearly 5 years.ResultsOur CRE collection comprised a diverse range of species, lineages, and carbapenem resistance mechanisms, many of which were encoded on a variety of promiscuous plasmid types. We found and quantified rearrangement, persistence, and repeated transfer of plasmid segments, including those harboring carbapenemases, between organisms over multiple years. Some plasmid segments were found to be strongly associated with specific locales, thus representing geographic signatures that make it possible to trace recent and localized HGT events. Functional analysis of these signatures revealed genes commonly found in plasmids of nosocomial pathogens, such as functions required for plasmid retention and spread, as well survival against a variety of antibiotic and antiseptics common to the hospital environment.ConclusionsCollectively, the framework we developed provides a clearer, high-resolution picture of the epidemiology of antibiotic resistance importation, spread, and persistence in patients and healthcare networks

The complete genome sequence of Chlorobium tepidum TLS, a photosynthetic, anaerobic, green-sulfur bacterium

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Distance trees of expression profiles.

<p>We constructed neighbor-joining trees based on the correlation between expression values (FPKM>1.0) between samples, with 1 minus Spearman's rho defining the distance. Colors denote library construction methods (poly-A: blue, DSN: red). We divided transcribed loci into (a) protein coding genes with RNA-Seq support, either annotated by EnsEMBL in dog or EnsEMBL in the human orthologous regions. Replicates cluster together, so do the library constructions methods poly-A and DSN, as well as related tissues, such as heart and muscle; (b) antisense transcripts, that overlap at least one exon of a protein coding gene, as defined in (a). With the exception of testis, poly-A and DSN separate the samples, with both the poly-A and DSN sub-trees maintaining closer relationships between the related tissues heart and muscle; (c) spliced intergenic loci, excluding sequences that have coding potential. Similar to protein coding genes, the poly-A and DSN group by tissue first, with the exception of kidney DSN; and (d) intergenic and uncharacterized single-exon transcript loci. In this set, DSN and poly-A are, similar to antisense loci, the most dominant factor when grouping samples.</p

Comparison of canFam2.0 and canFam3.1.

<p>Comparison of canFam2.0 and canFam3.1.</p