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July 7, 2019

Comparative and population genomic landscape of Phellinus noxius: A hypervariable fungus causing root rot in trees.

The order Hymenochaetales of white rot fungi contain some of the most aggressive wood decayers causing tree deaths around the world. Despite their ecological importance and the impact of diseases they cause, little is known about the evolution and transmission patterns of these pathogens. Here, we sequenced and undertook comparative genomic analyses of Hymenochaetales genomes using brown root rot fungus Phellinus noxius, wood-decomposing fungus Phellinus lamaensis, laminated root rot fungus Phellinus sulphurascens and trunk pathogen Porodaedalea pini. Many gene families of lignin-degrading enzymes were identified from these fungi, reflecting their ability as white rot fungi. Comparing against distant fungi highlighted the expansion of 1,3-beta-glucan synthases in P. noxius, which may account for its fast-growing attribute. We identified 13 linkage groups conserved within Agaricomycetes, suggesting the evolution of stable karyotypes. We determined that P. noxius has a bipolar heterothallic mating system, with unusual highly expanded ~60 kb A locus as a result of accumulating gene transposition. We investigated the population genomics of 60 P. noxius isolates across multiple islands of the Asia Pacific region. Whole-genome sequencing showed this multinucleate species contains abundant poly-allelic single nucleotide polymorphisms with atypical allele frequencies. Different patterns of intra-isolate polymorphism reflect mono-/heterokaryotic states which are both prevalent in nature. We have shown two genetically separated lineages with one spanning across many islands despite the geographical barriers. Both populations possess extraordinary genetic diversity and show contrasting evolutionary scenarios. These results provide a framework to further investigate the genetic basis underlying the fitness and virulence of white rot fungi.© 2017 John Wiley & Sons Ltd.


July 7, 2019

Complete genome sequence analysis of Enterobacter sp. SA187, a plant multi-stress tolerance promoting endophytic bacterium

Enterobacter sp. SA187 is an endophytic bacterium that has been isolated from root nodules of the indigenous desert plant Indigofera argentea. SA187 could survive in the rhizosphere as well as in association with different plant species, and was able to provide abiotic stress tolerance to Arabidopsis thaliana. The genome sequence of SA187 was obtained by using Pacific BioScience (PacBio) single-molecule sequencing technology, with average coverage of 275X. The genome of SA187 consists of one single 4,429,597 bp chromosome, with an average 56% GC content and 4,347 predicted protein coding DNA sequences (CDS), 153 ncRNA, 7 rRNA, and 84 tRNA. Functional analysis of the SA187 genome revealed a large number of genes involved in uptake and exchange of nutrients, chemotaxis, mobilization and plant colonization. A high number of genes were also found to be involved in survival, defense against oxidative stress and production of antimicrobial compounds and toxins. Moreover, different metabolic pathways were identified that potentially contribute to plant growth promotion. The information encoded in the genome of SA187 reveals the characteristics of a dualistic lifestyle of a bacterium that can adapt to different environments and promote the growth of plants. This information provides a better understanding of the mechanisms involved in plant-microbe interaction and could be further exploited to develop SA187 as a biological agent to improve agricultural practices in marginal and arid lands.


July 7, 2019

The genome sequence of Bipolaris cookei reveals mechanisms of pathogenesis underlying target leaf spot of sorghum.

Bipolaris cookei (=Bipolaris sorghicola) causes target leaf spot, one of the most prevalent foliar diseases of sorghum. Little is known about the molecular basis of pathogenesis in B. cookei, in large part due to a paucity of resources for molecular genetics, such as a reference genome. Here, a draft genome sequence of B. cookei was obtained and analyzed. A hybrid assembly strategy utilizing Illumina and Pacific Biosciences sequencing technologies produced a draft nuclear genome of 36.1?Mb, organized into 321 scaffolds with L50 of 31 and N50 of 378?kb, from which 11,189 genes were predicted. Additionally, a finished mitochondrial genome sequence of 135,790?bp was obtained, which contained 75 predicted genes. Comparative genomics revealed that B. cookei possessed substantially fewer carbohydrate-active enzymes and secreted proteins than closely related Bipolaris species. Novel genes involved in secondary metabolism, including genes implicated in ophiobolin biosynthesis, were identified. Among 37 B. cookei genes induced during sorghum infection, one encodes a putative effector with a limited taxonomic distribution among plant pathogenic fungi. The draft genome sequence of B. cookei provided novel insights into target leaf spot of sorghum and is an important resource for future investigation.


July 7, 2019

Chromosome level assembly and secondary metabolite potential of the parasitic fungus Cordyceps militaris.

Cordyceps militaris is an insect pathogenic fungus that is prized for its use in traditional medicine. This and other entomopathogenic fungi are understudied sources for the discovery of new bioactive molecules. In this study, PacBio SMRT long read sequencing technology was used to sequence the genome of C. militaris with a focus on the genetic potential for secondary metabolite production in the genome assembly of this fungus.This is first chromosome level assembly of a species in the Cordyceps genera. In this seven chromosome assembly of 33.6 Mba there were 9371 genes identified. Cordyceps militaris was determined to have the MAT 1-1-1 and MAT 1-1-2 mating type genes. Secondary metabolite analysis revealed the potential for at least 36 distinct metabolites from a variety of classes. Three of these gene clusters had homology with clusters producing desmethylbassianin, equisetin and emericellamide that had been studied in other fungi.Our assembly and analysis has revealed that C. militaris has a wealth of gene clusters for secondary metabolite production distributed among seven chromosomes. The identification of these gene clusters will facilitate the future study and identification of the secondary metabolites produced by this entomopathogenic fungus.


July 7, 2019

Complete genome sequencing and diversity analysis of lipolytic enzymes in Stenotrophomonas maltophilia OUC_Est10

[Objective] The aim of this study was to study the diversity of lipolytic enzymes in Stenotrophomonas maltophilia OUC_Est10. [Methods] Ion exchange chromatography, genome sequencing and heterologous expression were used to study the diversity of lipolytic enzymes in Stenotrophomonas maltophilia OUC_Est10. [Results] Stenotrophomonas maltophilia OUC_Est10 could secret a wide range of lipolytic enzymes (lipases and esterases) as revealed by ion exchange chromatography. The complete genome is of 4668743 bp in length, with an average GC content of 66.25%. Genome annotation indicated the presence of 33 candidate genes whose products possess the predicted lipolytic enzyme activities. Analysis of catalytic features was carried out by expressing five putative lipolytic enzyme genes, and lipolytic enzymes in OUC_Est10 had different catalytic properties. [Conclusion] We proved that Stenotrophomonas maltophilia OUC_Est10 was a good candidate to produce diverse lipolytic enzymes, with potential applications in various fields.


July 7, 2019

Complete genome sequence of Bacillus velezensis L-1, which has antagonistic activity against pear diseases.

Bacillus velezensis L-1 is an effective biocontrol agent against pear diseases. Here, we report the complete genome sequence of B. velezensis L-1 in which clusters related to the biosynthesis of secondary metabolites were predicted. This genome provides insights into the possible biocontrol mechanisms and furthers application of this specific bacterium. Copyright © 2017 Sun et al.


July 7, 2019

Safety evaluation of HOWARU®Restore (Lactobacillus acidophilus NCFM, Lactobacillus paracasei Lpc-37, Bifidobacterium animalis subsp. lactis Bl-04 and B. lactis Bi-07) for antibiotic resistance, genomic risk factors, and acute toxicity.

Although probiotic lactobacilli and bifidobacteria are generally considered safe by various regulatory agencies, safety properties, such as absence of transferable antibiotic resistance, must still be determined for each strain prior to market introduction as a probiotic. Safety requirements for probiotics vary regionally and evaluation methods are not standardized, therefore methodologies are often adopted from food ingredients or chemicals to assess microbial safety. Four individual probiotic strains, Lactobacillus acidophilus NCFM®, Lactobacillus paracasei Lpc-37®, Bifidobacterium animalis subsp. lactis strains Bl-04®, and Bi-07®, and their combination (HOWARU®Restore) were examined for antibiotic resistance by broth microdilution culture, toxin genes by PCR and genome mining, and acute oral toxicity in rats. Only B. lactis Bl-04 exhibited antibiotic resistance above a regulated threshold due to a tetW gene previously demonstrated to be non-transferable. Genomic mining did not reveal any bacterial toxin genes known to harm mammalian hosts in any of the strains. The rodent studies did not indicate any evidence of acute toxicity following a dose of 1.7-4.1 × 1012 CFU/kg body weight. Considering a 100-fold safety margin, this corresponds to 1.2-2.8 × 1012 CFU for a 70 kg human. Our findings demonstrate a comprehensive approach of in vitro, in silico, and in vivo safety testing for probiotics. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.


July 7, 2019

Complete genome sequence of Bacillus altitudinis P-10, a potential bioprotectant against Xanthomonas oryzae pv. oryzae, isolated from rice rhizosphere in Java, Indonesia.

Bacillus altitudinis P-10 was isolated from the rhizosphere of rice grown in an organic rice field and provides strong antagonism against the bacterial blight caused by Xanthomonas oryzae pv. oryzae in rice. Herein, we provide the complete genome sequence and a possible explanation of the antibiotic function of the P-10 strain.


July 7, 2019

Genome mining of astaxanthin biosynthetic genes from Sphingomonas sp. ATCC 55669 for heterologous overproduction in Escherichia coli.

As a highly valued keto-carotenoid, astaxanthin is widely used in nutritional supplements and pharmaceuticals. Therefore, the demand for biosynthetic astaxanthin and improved efficiency of astaxanthin biosynthesis has driven the investigation of metabolic engineering of native astaxanthin producers and heterologous hosts. However, microbial resources for astaxanthin are limited. In this study, we found that the a-Proteobacterium Sphingomonas sp. ATCC 55669 could produce astaxanthin naturally. We used whole-genome sequencing to identify the astaxanthin biosynthetic pathway using a combined PacBio-Illumina approach. The putative astaxanthin biosynthetic pathway in Sphingomonas sp. ATCC 55669 was predicted. For further confirmation, a high-efficiency targeted engineering carotenoid synthesis platform was constructed in E. coli for identifying the functional roles of candidate genes. All genes involved in astaxanthin biosynthesis showed discrete distributions on the chromosome. Moreover, the overexpression of exogenous E. coli idi in Sphingomonas sp. ATCC 55669 increased astaxanthin production by 5.4-fold. This study described a new astaxanthin producer and provided more biosynthesis components for bioengineering of astaxanthin in the future. © 2015 The Authors. Biotechnology Journal published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


July 7, 2019

Integrating mass spectrometry and genomics for cyanobacterial metabolite discovery.

Filamentous marine cyanobacteria produce bioactive natural products with both potential therapeutic value and capacity to be harmful to human health. Genome sequencing has revealed that cyanobacteria have the capacity to produce many more secondary metabolites than have been characterized. The biosynthetic pathways that encode cyanobacterial natural products are mostly uncharacterized, and lack of cyanobacterial genetic tools has largely prevented their heterologous expression. Hence, a combination of cutting edge and traditional techniques has been required to elucidate their secondary metabolite biosynthetic pathways. Here, we review the discovery and refined biochemical understanding of the olefin synthase and fatty acid ACP reductase/aldehyde deformylating oxygenase pathways to hydrocarbons, and the curacin A, jamaicamide A, lyngbyabellin, columbamide, and a trans-acyltransferase macrolactone pathway encoding phormidolide. We integrate into this discussion the use of genomics, mass spectrometric networking, biochemical characterization, and isolation and structure elucidation techniques.


July 7, 2019

Deciphering the streamlined genome of Streptomyces xiamenensis 318 as the producer of the anti-fibrotic drug candidate xiamenmycin.

Streptomyces xiamenensis 318, a moderate halophile isolated from a mangrove sediment, produces the anti-fibrotic compound xiamenmycin. The whole genome sequence of strain 318 was obtained through long-read single-molecule real-time (SMRT) sequencing, high-throughput Illumina HiSeq and 454 pyrosequencing technologies. The assembled genome comprises a linear chromosome as a single contig of 5,961,401-bp, which is considerably smaller than other reported complete genomes of the genus Streptomyces. Based on the antiSMASH pipeline, a total of 21?gene clusters were predicted to be involved in secondary metabolism. The gene cluster responsible for the biosynthesis of xiamenmycin resides in a strain-specific 61,387-bp genomic island belonging to the left-arm region. A core metabolic network consisting of 104 reactions that supports xiamenmycin biosynthesis was constructed to illustrate the necessary precursors derived from the central metabolic pathway. In accordance with the finding of a putative ikarugamycin gene cluster in the genome, the targeted chemical profiling of polycyclic tetramate macrolactams (PTMs) resulted in the identification of ikarugamycin. A successful genome mining for bioactive molecules with different skeletons suggests that the naturally minimized genome of S. xiamenensis 318 could be used as a blueprint for constructing a chassis cell with versatile biosynthetic capabilities for the production of secondary metabolites.


July 7, 2019

Complete genome sequence of Clostridium butyricum JKY6D1 isolated from the pit mud of a Chinese flavor liquor-making factory.

Clostridium butyricum is an important fragrance-producing bacterium in the traditional Chinese flavor liquor-making industry. Here the complete genome sequence of C. butyricum JKY6D1 isolated from the pit mud of a Chinese flavor liquor-making factory is presented. The genome is 4,618,327bp with the GC content of 28.74% and a plasmid of 8060bp. This is the first complete genome sequence of C. butyricum strains available so far. Copyright © 2016 Elsevier B.V. All rights reserved.


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