Menu
July 7, 2019

Precision medicine and rare genetic variants.

Interindividual variability in drug metabolism and drug toxicity persists as a major problem for drug development and treatment. Increased or decreased capacity for drug elimination or drug action reduces drug efficacy and places substantial economic burdens on society (e.g., due to treatment of adverse drug reactions) [1]. To a great extent this variation is based on genetic differences, and indeed many drugs now carry pharmacogenomic labels regarding mandatory or informative genetic tests that have to/can be performed before prescription (http://www.fda.gov/drugs/ scienceresearch/researchareas/pharmacogenetics/ucm083378.htm).Theselabelsarebasedonthe most common allelic variants in germline or somatic genes with importance for drug metabolism that encode phase I or phase II enzymes, transporters, or drug targets. In many cases, particularly in oncology, these labels are major determinants of successful treatment. However, the question arises of to what extent these labels are useful for future precision medicine encompassing specific patients carrying mutations not commonly seen in the whole population.


July 7, 2019

Identifying potential mechanisms enabling acidophily in the ammonia-oxidising archaeon ‘Candidatus Nitrosotalea devanaterra’.

Ammonia oxidation is the first and rate-limiting step in nitrification and is dominated by two distinct groups of microorganisms in soil: ammonia-oxidising archaea (AOA) and bacteria (AOB). AOA are often more abundant than AOB, and dominate activity in acid soils. The mechanism of ammonia oxidation in acidic conditions has been a long-standing paradox. While high rates of ammonia oxidation are frequently measured in acid soils, cultivated ammonia oxidisers only grew at near-neutral pH when grown in standard laboratory culture. Although a number of mechanisms have been demonstrated to enable neutrophilic AOB growth at low pH in the laboratory, these have not been demonstrated in soil, and the recent cultivation of the obligately acidophilic ammonia oxidiser ‘Candidatus Nitrosotalea devanaterra’ provides a more parsimonious explanation for the observed high rates of activity. Analysis of the sequenced genome, transcriptional activity and lipid content of ‘Ca. N. devanaterra’ reveals that previously proposed mechanisms used by AOB for growth at low pH are not essential for archaeal ammonia oxidation in acidic environments. Instead, the genome indicates that ‘Ca. N. devanaterra’ contains genes encoding both a predicted high-affinity substrate acquisition system and potential pH homeostasis mechanisms absent in neutrophilic AOA. Analysis of mRNA revealed that candidate genes encoding for the proposed homeostasis mechanisms were all expressed during acidophilic growth, and lipid profiling by HPLC-MS demonstrated that the membrane lipids of ‘Ca. N. devanaterra’ were not dominated by crenarchaeol, as found in neutrophilic AOA. This study describes the first genome of an obligately acidophilic ammonia oxidiser and identifies potential mechanisms enabling this unique phenotype for future biochemical characterisation. Copyright © 2016 Lehtovirta-Morley et al.


July 7, 2019

Population structure and acquisition of the vanB resistance determinant in German clinical isolates of Enterococcus faecium ST192.

In the context of the global action plan to reduce the dissemination of antibiotic resistances it is of utmost importance to understand the population structure of resistant endemic bacterial lineages and to elucidate how bacteria acquire certain resistance determinants. Vancomycin resistant enterococci represent one such example of a prominent nosocomial pathogen on which nation-wide population analyses on prevalent lineages are scarce and data on how the bacteria acquire resistance, especially of the vanB genotype, are still under debate. With respect to Germany, an increased prevalence of VRE was noted in recent years. Here, invasive infections caused by sequence type ST192 VRE are often associated with the vanB-type resistance determinant. Hence, we analyzed 49 vanB-positive and vanB-negative E. faecium isolates by means of whole genome sequencing. Our studies revealed a distinct population structure and that spread of the Tn1549-vanB-type resistance involves exchange of large chromosomal fragments between vanB-positive and vanB-negative enterococci rather than independent acquisition events. In vitro filter-mating experiments support the hypothesis and suggest the presence of certain target sequences as a limiting factor for dissemination of the vanB element. Thus, the present study provides a better understanding of how enterococci emerge into successful multidrug-resistant nosocomial pathogens.


July 7, 2019

The genome analysis of Candidatus Burkholderia crenata reveals that secondary metabolism may be a key function of the Ardisia crenata leaf nodule symbiosis.

A majority of Ardisia species harbour Burkholderia sp. bacteria within specialized leaf nodules. The bacteria are transmitted hereditarily and have not yet been cultured outside of their host. Because the plants cannot develop beyond the seedling stage without their symbionts, the symbiosis is considered obligatory. We sequenced for the first time the genome of Candidatus Burkholderia crenata (Ca. B. crenata), the leaf nodule symbiont of Ardisia crenata. The genome of Ca. B. crenata is the smallest Burkholderia genome to date. It contains a large amount of insertion sequences and pseudogenes and displays features consistent with reductive genome evolution. The genome does not encode functions commonly associated with plant symbioses such as nitrogen fixation and plant hormone metabolism. However, we identified unique genes with a predicted role in secondary metabolism in the genome of Ca. B. crenata. Specifically, we provide evidence that the bacterial symbionts are responsible for the synthesis of compound FR900359, a cyclic depsipeptide with biomedical properties previously isolated from leaves of A.?crenata. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.


July 7, 2019

Exocytotic fusion pores are composed of both lipids and proteins.

During exocytosis, fusion pores form the first aqueous connection that allows escape of neurotransmitters and hormones from secretory vesicles. Although it is well established that SNARE proteins catalyze fusion, the structure and composition of fusion pores remain unknown. Here, we exploited the rigid framework and defined size of nanodiscs to interrogate the properties of reconstituted fusion pores, using the neurotransmitter glutamate as a content-mixing marker. Efficient Ca(2+)-stimulated bilayer fusion, and glutamate release, occurred with approximately two molecules of mouse synaptobrevin 2 reconstituted into ~6-nm nanodiscs. The transmembrane domains of SNARE proteins assumed distinct roles in lipid mixing versus content release and were exposed to polar solvent during fusion. Additionally, tryptophan substitutions at specific positions in these transmembrane domains decreased glutamate flux. Together, these findings indicate that the fusion pore is a hybrid structure composed of both lipids and proteins.


July 7, 2019

The emergence and intercontinental spread of a multidrug-resistant clade of typhoid agent Salmonella enterica serovar Typhi

Multidrug-resistant typhoid is a global health problem. Previous studies conducted in countries of Asia and Africa have identified a highly clonal, multidrug-resistant lineage of Salmonella enterica serovar Typhi (S Typhi), known as H58. However, little is known about the emergence and geographical spread of the H58 clade. In this study, we have used whole-genome sequencing of a global collection of S Typhi to investigate this highly successful lineage.


July 7, 2019

Population structure and antimicrobial resistance profiles of Streptococcus suis serotype 2 sequence type 25 strains

Strains of serotype 2 Streptococcus suis are responsible for swine and human infections. Different serotype 2 genetic backgrounds have been defined using multilocus sequence typing (MLST). However, little is known about the genetic diversity within each MLST sequence type (ST). Here, we used whole-genome sequencing to test the hypothesis that S. suis serotype 2 strains of the ST25 lineage are genetically heterogeneous. We evaluated 51 serotype 2 ST25 S. suis strains isolated from diseased pigs and humans in Canada, the United States of America, and Thailand. Whole-genome sequencing revealed numerous large-scale rearrangements in the ST25 genome, compared to the genomes of ST1 and ST28 S. suis strains, which result, among other changes, in disruption of a pilus island locus. We report that recombination and lateral gene transfer contribute to ST25 genetic diversity. Phylogenetic analysis identified two main and distinct Thai and North American clades grouping most strains investigated. These clades also possessed distinct patterns of antimicrobial resistance genes, which correlated with acquisition of different integrative and conjugative elements (ICEs). Some of these ICEs were found to be integrated at a recombination hot spot, previously identified as the site of integration of the 89K pathogenicity island in serotype 2 ST7 S. suis strains. Our results highlight the limitations of MLST for phylogenetic analysis of S. suis, and the importance of lateral gene transfer and recombination as drivers of diversity in this swine pathogen and zoonotic agent.


July 7, 2019

Genomic and transcriptomic analysis of the streptomycin-dependent Mycobacterium tuberculosis strain 18b.

The ability of Mycobacterium tuberculosis to establish a latent infection (LTBI) in humans confounds the treatment of tuberculosis. Consequently, there is a need to discover new therapeutic agents that can kill M. tuberculosis both during active disease and LTBI. The streptomycin-dependent strain of M. tuberculosis, 18b, provides a useful tool for this purpose since upon removal of streptomycin (STR) it enters a non-replicating state that mimics latency both in vitro and in animal models.The 4.41 Mb genome sequence of M. tuberculosis 18b was determined and this revealed the strain to belong to clade 3 of the ancient ancestral lineage of the Beijing family. STR-dependence was attributable to insertion of a single cytosine in the 530 loop of the 16S rRNA and to a single amino acid insertion in the N-terminal domain of initiation factor 3. RNA-seq was used to understand the genetic programme activated upon STR-withdrawal and hence to gain insight into LTBI. This revealed reconfiguration of gene expression and metabolic pathways showing strong similarities between non-replicating 18b and M. tuberculosis residing within macrophages, and with the core stationary phase and microaerophilic responses.The findings of this investigation confirm the validity of 18b as a model for LTBI, and provide insight into both the evolution of tubercle bacilli and the functioning of the ribosome.


July 7, 2019

Insights into adaptations to a near-obligate nematode endoparasitic lifestyle from the finished genome of Drechmeria coniospora.

Nematophagous fungi employ three distinct predatory strategies: nematode trapping, parasitism of females and eggs, and endoparasitism. While endoparasites play key roles in controlling nematode populations in nature, their application for integrated pest management is hindered by the limited understanding of their biology. We present a comparative analysis of a high quality finished genome assembly of Drechmeria coniospora, a model endoparasitic nematophagous fungus, integrated with a transcriptomic study. Adaptation of D. coniospora to its almost completely obligate endoparasitic lifestyle led to the simplification of many orthologous gene families involved in the saprophytic trophic mode, while maintaining orthologs of most known fungal pathogen-host interaction proteins, stress response circuits and putative effectors of the small secreted protein type. The need to adhere to and penetrate the host cuticle led to a selective radiation of surface proteins and hydrolytic enzymes. Although the endoparasite has a simplified secondary metabolome, it produces a novel peptaibiotic family that shows antibacterial, antifungal and nematicidal activities. Our analyses emphasize the basic malleability of the D. coniospora genome: loss of genes advantageous for the saprophytic lifestyle; modulation of elements that its cohort species utilize for entomopathogenesis; and expansion of protein families necessary for the nematode endoparasitic lifestyle.


July 7, 2019

Global phylogeography and evolutionary history of Shigella dysenteriae type 1

Together with plague, smallpox and typhus, epidemics of dysentery have been a major scourge of human populations for centuries1. A previous genomic study concluded that Shigella dysenteriae type 1 (Sd1), the epidemic dysentery bacillus, emerged and spread worldwide after the First World War, with no clear pattern of transmission2. This is not consistent with the massive cyclic dysentery epidemics reported in Europe during the eighteenth and nineteenth centuries1,3,4 and the first isolation of Sd1 in Japan in 18975. Here, we report a whole-genome analysis of 331 Sd1 isolates from around the world, collected between 1915 and 2011, providing us with unprecedented insight into the historical spread of this pathogen. We show here that Sd1 has existed since at least the eighteenth century and that it swept the globe at the end of the nineteenth century, diversifying into distinct lineages associated with the First World War, Second World War and various conflicts or natural disasters across Africa, Asia and Central America. We also provide a unique historical perspective on the evolution of antibiotic resistance over a 100-year period, beginning decades before the antibiotic era, and identify a prevalent multiple antibiotic-resistant lineage in South Asia that was transmitted in several waves to Africa, where it caused severe outbreaks of disease.


July 7, 2019

Recurrent DUX4 fusions in B cell acute lymphoblastic leukemia of adolescents and young adults.

The oncogenic mechanisms underlying acute lymphoblastic leukemia (ALL) in adolescents and young adults (AYA; 15-39 years old) remain largely elusive. Here we have searched for new oncogenes in AYA-ALL by performing RNA-seq analysis of Philadelphia chromosome (Ph)-negative AYA-ALL specimens (n = 73) with the use of a next-generation sequencer. Interestingly, insertion of D4Z4 repeats containing the DUX4 gene into the IGH locus was frequently identified in B cell AYA-ALL, leading to a high level of expression of DUX4 protein with an aberrant C terminus. A transplantation assay in mice demonstrated that expression of DUX4-IGH in pro-B cells was capable of generating B cell leukemia in vivo. DUX4 fusions were preferentially detected in the AYA generation. Our data thus show that DUX4 can become an oncogenic driver as a result of somatic chromosomal rearrangements and that AYA-ALL may be a clinical entity distinct from ALL at other ages.


July 7, 2019

Complete genome sequence analysis of Pandoraea pnomenusa type strain DSM 16536(T) isolated from a cystic fibrosis patient.

The genus of Pandoraea was first proposed in 2000 following the isolation from the sputum of cystic fibrosis patients (Coenye et al., 2000). Five species were initially assigned to the novel genus namely Pandoraea apista, Pandoraea pulmonicola, Pandoraea pnomenusa, Pandoraea sputorum, and Pandoraea norimbergensis but the description of four new species and another four genomospecies in the subsequent years led to a total of nine species and four genomospecies within the genus of Pandoraea (Daneshvar et al., 2001; Anandham et al., 2010; Sahin et al., 2011). The isolation of Pandoraea spp. from various environmental samples such as water, sludge, and soils have been reported, but to date, only P. pnomenusa, P. apista, P. pulmonicola, and P. sputorum were isolated from clinical specimens such as blood, sputum and bronchial fluid of patients with cystic fibrosis or chronic lung diseases (Coenye et al., 2000; Daneshvar et al., 2001; Stryjewski et al., 2003; Han-Jen et al., 2013). Members of Pandoraea tend to exhibit broad resistance to ampicillin, extended-spectrum cephalosporins, aztreonam, aminoglycosides, and meropenem but they are sensitive to imipenem (Daneshvar et al., 2001; Stryjewski et al., 2003). However, the clinical significance and prevalence of these multi-drug resistant bacteria among patients with cystic fibrosis or respiratory diseases remained unknown since Pandoraea spp. are usually misidentified as Burkholderia cepacia complex, Ralstonia pickettii, or Ralstonia paucula (Segonds et al., 2003). Ambiguity in differentiating between B. cepacia complex, Ralstonia spp. and Pandoraea spp. can be resolved by 16S ribosomal DNA-PCR (Coenye et al., 2001) and gyrB gene restriction fragment length polymorphism (Coenye and LiPuma, 2002) but the limited use of molecular typing methods in routine clinical microbiological laboratory has resulted in the underreporting of Pandoraea spp. in clinical cases.


July 7, 2019

Whole genome sequence of Pantoea ananatis R100, an antagonistic bacterium isolated from rice seed.

Pantoea ananatis is a group of bacteria, which was first reported as plant pathogen. Recently, several papers also described its biocontrol ability. In 2003, P. ananatis R100, which showed strong antagonism against several plant pathogens, was isolated from rice seeds. In this study, whole genome sequence of this strain was determined by SMRT Cell technology. The total genome size of R100 is 4,857,861bp with 4659 coding genes (CDS), 82 tRNAs and 22 rRNAs. The genome sequence of R100 may shed a light on the research of antagonism P. ananatis. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.


July 7, 2019

Complete genome sequence of Lactobacillus helveticus CAUH18, a potential probiotic strain originated from koumiss.

Here we report the complete genome sequence of Lactobacillus helveticus CAUH18, a new strain isolated from traditional fermented dairy product koumiss. Its genome has a circular 2.16Mb chromosome with no plasmid. The genome sequence indicated that this strain harbors a gene cluster involved in a novel exopolysaccharides (EPS) biosynthesis and a gene encoding cell-surface aggregation-promoting factors (APFs) to facilitate its colonization in gastrointestinal tract (GIT). This genome sequence provides a basis for further studies about its molecular genetics and probiotic functions. Copyright © 2016. Published by Elsevier B.V.


Talk with an expert

If you have a question, need to check the status of an order, or are interested in purchasing an instrument, we're here to help.