Menu

Auto Tag: Evolution

September 22, 2019

Comparative genomic analysis revealed rapid differentiation in the pathogenicity-related gene repertoires between Pyricularia oryzae and Pyricularia penniseti isolated from a Pennisetum grass.

A number of Pyricularia species are known to infect different grass species. In the case of Pyricularia oryzae (syn. Magnaporthe oryzae), distinct populations are known to be adapted to a wide variety of grass hosts, including rice, wheat and many other grasses. The genome sizes of Pyricularia species are typical for filamentous ascomycete fungi [~?40 Mbp for P. oryzae, and ~?45 Mbp for P. grisea]. Genome plasticity, mediated in part by deletions promoted by recombination between repetitive elements [Genome Res 26:1091-1100, 2016, Nat Rev Microbiol 10:417-430,2012] and transposable elements [Annu Rev Phytopathol 55:483-503,2017] contributes to host adaptation. Therefore, comparisons of genome structure of individual species will provide insight into the evolution of host specificity. However, except for the P. oryzae subgroup, little is known about the gene content or genome organization of other Pyricularia species, such as those infecting Pennisetum grasses.Here, we report the genome sequence of P. penniseti strain P1609 isolated from a Pennisetum grass (JUJUNCAO) using PacBio SMRT sequencing technology. Phylogenomic analysis of 28 Magnaporthales species and 5 non-Magnaporthales species indicated that P1609 belongs to a Pyricularia subclade, which is genetically distant from P. oryzae. Comparative genomic analysis revealed that the pathogenicity-related gene repertoires had diverged between P1609 and the P. oryzae strain 70-15, including the known avirulence genes, other putative secreted proteins, as well as some other predicted Pathogen-Host Interaction (PHI) genes. Genomic sequence comparison also identified many genomic rearrangements relative to P. oryzae.Our results suggested that the genomic sequence of the P. penniseti P1609 could be a useful resource for the genetic study of the Pennisetum-infecting Pyricularia species and provide new insight into evolution of pathogen genomes during host adaptation.

Read more
September 22, 2019

Impact of index hopping and bias towards the reference allele on accuracy of genotype calls from low-coverage sequencing.

Inherent sources of error and bias that affect the quality of sequence data include index hopping and bias towards the reference allele. The impact of these artefacts is likely greater for low-coverage data than for high-coverage data because low-coverage data has scant information and many standard tools for processing sequence data were designed for high-coverage data. With the proliferation of cost-effective low-coverage sequencing, there is a need to understand the impact of these errors and bias on resulting genotype calls from low-coverage sequencing.We used a dataset of 26 pigs sequenced both at 2× with multiplexing and at 30× without multiplexing to show that index hopping and bias towards the reference allele due to alignment had little impact on genotype calls. However, pruning of alternative haplotypes supported by a number of reads below a predefined threshold, which is a default and desired step of some variant callers for removing potential sequencing errors in high-coverage data, introduced an unexpected bias towards the reference allele when applied to low-coverage sequence data. This bias reduced best-guess genotype concordance of low-coverage sequence data by 19.0 absolute percentage points.We propose a simple pipeline to correct the preferential bias towards the reference allele that can occur during variant discovery and we recommend that users of low-coverage sequence data be wary of unexpected biases that may be produced by bioinformatic tools that were designed for high-coverage sequence data.

Read more
September 22, 2019

Quaternary ammonium compounds with multiple cationic moieties (multiQACs) provide antimicrobial activity against Campylobacter jejuni

Recently developed quaternary ammonium compounds (QACs) possessing multiple cationic moieties, referred to as multiQACs, were tested with strains of Campylobacter jejuni to determine their potential as antimicrobial compounds against this important foodborne pathogen. Eight multiQACs were tested against a cocktail of six C. jejuni strains isolated from environmental and clinical sources. The resulting reductions in C. jejuni numbers mediated by the multiQACs were compared to the reductions produced by the application of four commercially available QACs, each of which bears a single cation. Multiple concentrations and exposure times were utilized for all compounds. The compounds which yielded the maximum C. jejuni reductions at the lowest concentrations and applied over the shortest exposure times were judged to be the most successful. Of the eight multiQACs investigated, four demonstrated reductions in C. jejuni numbers superior to the commercial QACs; these four are biscationic, and two of them bear an additional uncharged nitrogen atom. The remaining four multiQACs, which contain three or four cations, did not produce reductions in bacterial numbers comparable to commercial QACs in the timeframes tested. At the intermediary compound concentration (0.05?mM) and exposure time (5?min) the most effective multiQACs (PQ-12,12 and 12(3)0(3)12) on average killed over 99% of the Campylobacter cells present while the best commercial compound at those parameters (cetyl pyridinium chloride, CPC) only killed on average 84.56% of the Campylobacter cells. At the highest compound concentration tested (0.1?mM) and shortest exposure time (1?min), the same two biscationic multiQACs averaged mean percent reductions of Campylobacter cell numbers around 99.5% while CPC at the same concentration/exposure only managed a percent reduction of 91.3%. The biscationic multiQACs demonstrate the potential for providing a new group of antimicrobial compounds superior to current commercially available QACs in their effectiveness against C. jejuni.

Read more
September 22, 2019

Novel energy conservation strategies and behaviour of Pelotomaculum schinkii driving syntrophic propionate catabolism.

Under methanogenic conditions, short-chain fatty acids are common byproducts from degradation of organic compounds and conversion of these acids is an important component of the global carbon cycle. Due to the thermodynamic difficulty of propionate degradation, this process requires syntrophic interaction between a bacterium and partner methanogen; however, the metabolic strategies and behaviour involved are not fully understood. In this study, the first genome analysis of obligately syntrophic propionate degraders (Pelotomaculum schinkii HH and P. propionicicum MGP) and comparison with other syntrophic propionate degrader genomes elucidated novel components of energy metabolism behind Pelotomaculum propionate oxidation. Combined with transcriptomic examination of P. schinkii behaviour in co-culture with Methanospirillum hungatei, we found that formate may be the preferred electron carrier for P. schinkii syntrophy. Propionate-derived menaquinol may be primarily re-oxidized to formate, and energy was conserved during formate generation through newly proposed proton-pumping formate extrusion. P. schinkii did not overexpress conventional energy metabolism associated with a model syntrophic propionate degrader Syntrophobacter fumaroxidans MPOB (i.e., CoA transferase, Fix and Rnf). We also found that P. schinkii and the partner methanogen may also interact through flagellar contact and amino acid and fructose exchange. These findings provide new understanding of syntrophic energy acquisition and interactions.© 2018 Society for Applied Microbiology and John Wiley & Sons Ltd.

Read more
September 22, 2019

Meiotic drive of female-inherited supernumerary chromosomes in a pathogenic fungus.

Meiosis is a key cellular process of sexual reproduction that includes pairing of homologous sequences. In many species however, meiosis can also involve the segregation of supernumerary chromosomes, which can lack a homolog. How these unpaired chromosomes undergo meiosis is largely unknown. In this study we investigated chromosome segregation during meiosis in the haploid fungus Zymoseptoria tritici that possesses a large complement of supernumerary chromosomes. We used isogenic whole chromosome deletion strains to compare meiotic transmission of chromosomes when paired and unpaired. Unpaired chromosomes inherited from the male parent as well as paired supernumerary chromosomes in general showed Mendelian inheritance. In contrast, unpaired chromosomes inherited from the female parent showed non-Mendelian inheritance but were amplified and transmitted to all meiotic products. We concluded that the supernumerary chromosomes of Z. tritici show a meiotic drive and propose an additional feedback mechanism during meiosis, which initiates amplification of unpaired female-inherited chromosomes.© 2018, Habig et al.

Read more
September 22, 2019

Insights into the biology of acidophilic members of the Acidiferrobacteraceae family derived from comparative genomic analyses.

The family Acidiferrobacteraceae (order Acidiferrobacterales) currently contains Gram negative, neutrophilic sulfur oxidizers such as Sulfuricaulis and Sulfurifustis, as well as acidophilic iron and sulfur oxidizers belonging to the Acidiferrobacter genus. The diversity and taxonomy of the genus Acidiferrobacter has remained poorly explored. Although several metagenome and bioleaching studies have identified its presence worldwide, only two strains, namely Acidiferrobacter thiooxydans DSM 2932T, and Acidiferrobacter spp. SP3/III have been isolated and made publically available. Using 16S rRNA sequence data publically available for the Acidiferrobacteraceae, we herein shed light into the molecular taxonomy of this family. Results obtained support the presence of three clades Acidiferrobacter, Sulfuricaulis and Sulfurifustis. Genomic analyses of the genome sequences of A. thiooxydansT and Acidiferrobacter spp. SP3/III indicate that ANI relatedness between the SPIII/3 strain and A. thiooxydansT is below 95-96%, supporting the classification of strain SP3/III as a new species within this genus. In addition, approximately 70% of Acidiferrobacter sp. SPIII/3 predicted genes have a conserved ortholog in A. thiooxydans strains. A comparative analysis of iron, sulfur oxidation pathways, genome plasticity and cell-cell communication mechanisms of Acidiferrobacter spp. are also discussed. Copyright © 2018 The Authors. Published by Elsevier Masson SAS.. All rights reserved.

Read more
September 22, 2019

The Genome of Opium Poppy Reveals Evolutionary History of Morphinan Pathway.

Plants, as primary producers, have been playing an indispensable role in other organisms’ survival and the balance of whole ecosystem on Earth. Especially, they provide the main source of energy, food, and medicine for human beings, some of which are derived from the primary or secondary metabolites [1]. Angiosperms, with more than 300,000 species on Earth, are the largest group of land plants by far. Most agricultural crops, fruits, ornamental plants, and medicinal herbs belong to this group. The medicinal herbs are usually rich in specialized metabolites that could provide safe and valuable resources for pharmaceutical development.

Read more
September 22, 2019

Cloning and characterization of short-chain N-acyl homoserine lactone-producing Enterobacter asburiae strain L1 from lettuce leaves.

In gram-negative bacteria, bacterial communication or quorum sensing (QS) is achieved using common signaling molecules known as N-acyl homoserine lactones (AHL). We have previously reported the genome of AHL-producing bacterium, Enterobacter asburiae strain L1. In silico analysis of the strain L1 genome revealed the presence of a pair of luxI/R genes responsible for AHL-type QS, designated as easIR. In this work, the 639 bp luxI homolog, encoding 212 amino acids, have been cloned and overexpressed in Escherichia coli BL21 (DE3)pLysS. The purified protein (~25 kDa) shares high similarity to several members of the LuxI family among different E asburiae strains. Our findings showed that the heterologously expressed EasI protein has activated violacein production by AHL biosensor Chromobacterium violaceum CV026 as the wild-type E. asburiae. The mass spectrometry analysis showed the production of N-butanoyl homoserine lactone and N-hexanoyl homoserine lactone from induced E. coli harboring the recombinant EasI, suggesting that EasI is a functional AHL synthase. E. asburiae strain L1 was also shown to possess biofilm-forming characteristic activity using crystal violet binding assay. This is the first report on cloning and characterization of the luxI homolog from E. asburiae.© 2018 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.

Read more
September 22, 2019

Complete genome sequence of Leuconostoc citreum EFEL2700, a host strain for transformation of pCB vectors.

Leuconostoc citreum is an important lactic acid bacterium used as a starter culture for producing kimchi, the traditional Korean fermented vegetables. An efficient host strain for plasmid transformation, L. citreum EFEL2700, was isolated from kimchi, and it has been frequently used for genetic engineering of L. citreum. In this study, we report the whole genome sequence of the strain and its genetic characteristics. Genome assembly yielded 5 contigs (1 chromosome and 4 plasmids), and the complete genome contained 1,923,830 base pairs (bp) with a G?+?C content of 39.0%. Average nucleotide identity analysis showed high homology (= 99%) to the reference strain L. citreum KM 20. The smallest plasmid (4.3 kbp) was used as an Escherichia coli shuttle vector (pCB) for heterologous gene expression, and L. citreum EFEL2700 showed the highest transformation efficiency, 6.7?×?104 CFU µg-1 DNA. Genetic analysis of the genome enabled the construction of primary metabolic pathway showing a typical hetero-type lactic acid fermentation. Notably, no core genes for primary metabolism were observed in plasmid 4 and it could be eliminated to create an efficient host for gene transformation. This report will facilitate the understanding and application of L. citreum EFEL2700 as a food-grade microbial cell factory.Copyright © 2018. Published by Elsevier B.V.

Read more
September 22, 2019

Implications of stx loss for clinical diagnostics of Shiga toxin-producing Escherichia coli.

The dynamics related to the loss of stx genes from Shiga toxin-producing Escherichia coli remain unclear. Current diagnostic procedures have shortcomings in the detection and identification of STEC. This is partly owing to the fact that stx genes may be lost during an infection or in the laboratory. The aim of the present study was to provide new insight into in vivo and in vitro stx loss in order to improve diagnostic procedures. Results from the study support the theory that loss of stx is a strain-related phenomenon and not induced by patient factors. It was observed that one strain could lose stx both in vivo and in vitro. Whole genome comparison of stx-positive and stx-negative isolates from the same patient revealed that different genomic rearrangements, such as complete or partial loss of the parent prophage, may be factors in the loss of stx. Of diagnostic interest, it was shown that patients can be co-infected with different E. coli pathotypes. Therefore, identification of eae-positive, but stx-negative isolates should not be interpreted as “Shiga toxin-lost” E. coli without further testing. Growth and recovery of STEC were supported by different selective agar media for different strains, arguing for inclusion of several media in STEC diagnostics.

Read more
September 22, 2019

A large, refractory nosocomial outbreak of Klebsiella pneumoniae carbapenemase (KPC)-producing Escherichia coli demonstrates carbapenemase gene outbreaks involving sink sites require novel approaches to infection control.

Carbapenem-resistant Enterobacteriaceae (CRE) represent a health threat, but effective control interventions remain unclear. Hospital wastewater sites are increasingly being highlighted as important potential reservoirs. We investigated a large Klebsiella pneumoniae carbapenemase (KPC)-producing Escherichia coli outbreak and wider CRE incidence trends in the Central Manchester University Hospital NHS Foundation Trust (CMFT) (United Kingdom) over 8 years, to determine the impact of infection prevention and control measures. Bacteriology and patient administration data (2009 to 2017) were linked, and a subset of CMFT or regional hospital KPC-producing E. coli isolates (n = 268) were sequenced. Control interventions followed international guidelines and included cohorting, rectal screening (n = 184,539 screens), environmental sampling, enhanced cleaning, and ward closure and plumbing replacement. Segmented regression of time trends for CRE detections was used to evaluate the impact of interventions on CRE incidence. Genomic analysis (n = 268 isolates) identified the spread of a KPC-producing E. coli outbreak clone (strain A, sequence type 216 [ST216]; n = 125) among patients and in the environment, particularly on 2 cardiac wards (wards 3 and 4), despite control measures. ST216 strain A had caused an antecedent outbreak and shared its KPC plasmids with other E. coli lineages and Enterobacteriaceae species. CRE acquisition incidence declined after closure of wards 3 and 4 and plumbing replacement, suggesting an environmental contribution. However, ward 3/ward 4 wastewater sites were rapidly recolonized with CRE and patient CRE acquisitions recurred, albeit at lower rates. Patient relocation and plumbing replacement were associated with control of a clonal KPC-producing E. coli outbreak; however, environmental contamination with CRE and patient CRE acquisitions recurred rapidly following this intervention. The large numbers of cases and the persistence of blaKPC in E. coli, including pathogenic lineages, are of concern. Copyright © 2018 American Society for Microbiology.

Read more
September 22, 2019

Investigation of inter- and intraspecies variation through genome sequencing of Aspergillus section Nigri.

Aspergillus section Nigri comprises filamentous fungi relevant to biomedicine, bioenergy, health, and biotechnology. To learn more about what genetically sets these species apart, as well as about potential applications in biotechnology and biomedicine, we sequenced 23 genomes de novo, forming a full genome compendium for the section (26 species), as well as 6 Aspergillus niger isolates. This allowed us to quantify both inter- and intraspecies genomic variation. We further predicted 17,903 carbohydrate-active enzymes and 2,717 secondary metabolite gene clusters, which we condensed into 455 distinct families corresponding to compound classes, 49% of which are only found in single species. We performed metabolomics and genetic engineering to correlate genotypes to phenotypes, as demonstrated for the metabolite aurasperone, and by heterologous transfer of citrate production to Aspergillus nidulans. Experimental and computational analyses showed that both secondary metabolism and regulation are key factors that are significant in the delineation of Aspergillus species.

Read more
September 22, 2019

Whole-genome landscape of Medicago truncatula symbiotic genes.

Advances in deciphering the functional architecture of eukaryotic genomes have been facilitated by recent breakthroughs in sequencing technologies, enabling a more comprehensive representation of genes and repeat elements in genome sequence assemblies, as well as more sensitive and tissue-specific analyses of gene expression. Here we show that PacBio sequencing has led to a substantially improved genome assembly of Medicago truncatula A17, a legume model species notable for endosymbiosis studies1, and has enabled the identification of genome rearrangements between genotypes at a near-base-pair resolution. Annotation of the new M. truncatula genome sequence has allowed for a thorough analysis of transposable elements and their dynamics, as well as the identification of new players involved in symbiotic nodule development, in particular 1,037 upregulated long non-coding RNAs (lncRNAs). We have also discovered that a substantial proportion (~35% and 38%, respectively) of the genes upregulated in nodules or expressed in the nodule differentiation zone colocalize in genomic clusters (270 and 211, respectively), here termed symbiotic islands. These islands contain numerous expressed lncRNA genes and display differentially both DNA methylation and histone marks. Epigenetic regulations and lncRNAs are therefore attractive candidate elements for the orchestration of symbiotic gene expression in the M. truncatula genome.

Read more
September 22, 2019

Density-dependent enhanced replication of a densovirus in Wolbachia-infected Aedes cells is associated with production of piRNAs and higher virus-derived siRNAs.

The endosymbiotic bacterium Wolbachia pipientis has been shown to restrict a range of RNA viruses in Drosophila melanogaster and transinfected dengue mosquito, Aedes aegypti. Here, we show that Wolbachia infection enhances replication of Aedes albopictus densovirus (AalDNV-1), a single stranded DNA virus, in Aedes cell lines in a density-dependent manner. Analysis of previously produced small RNAs of Aag2 cells showed that Wolbachia-infected cells produced greater absolute abundance of virus-derived short interfering RNAs compared to uninfected cells. Additionally, we found production of virus-derived PIWI-like RNAs (vpiRNA) produced in response to AalDNV-1 infection. Nuclear fractions of Aag2 cells produced a primary vpiRNA signature U1 bias whereas the typical “ping-pong” signature (U1 – A10) was evident in vpiRNAs from the cytoplasmic fractions. This is the first report of the density-dependent enhancement of DNA viruses by Wolbachia. Further, we report the generation of vpiRNAs in a DNA virus-host interaction for the first time. Copyright © 2018 Elsevier Inc. All rights reserved.

Read more
September 22, 2019

Genomic characterization of carbapenemase-producing Klebsiella pneumoniae with chromosomally encoded blaNDM-1.

We report here Klebsiella pneumoniae strains carrying chromosomal blaNDM-1 in Thailand. The genomes of these two isolates include a 160-kbp insertion containing blaNDM-1, which is almost identical to that in the IncHI1B-like plasmid. Further analysis indicated that IS5-mediated intermolecular transposition and Tn3 transposase-mediated homologous recombination resulted in the integration of blaNDM-1 into the chromosome from an IncHI1B-like plasmid. The spread of this type of carbapenem-resistant Enterobacteriaceae may threaten public health and warrants further monitoring. Copyright © 2018 American Society for Microbiology.

Read more

Subscribe for blog updates:

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.