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July 7, 2019

Genetic characterization of a blaVEB-2-carrying plasmid in Vibrio parahaemolyticus.

This study reports the first detection of blaVEB-2 gene in Vibrio parahaemolyticus strain isolated from a shrimp sample. The blaVEB-2 was carried on a novel Inc type plasmid, was likely to originate from aquatic organisms upon comparison with other known genetic elements in the GenBank. However, the plasmid contains resistance elements usually harbored by members of Enterobacteriaceae, suggesting that gene transfer events occurred and contributed to the formation of this multidrug resistance-encoding plasmid. Copyright © 2016, American Society for Microbiology. All Rights Reserved.


July 7, 2019

The complete genome sequences of sulfur-oxidizing Gammaproteobacteria Sulfurifustis variabilis skN76(T) and Sulfuricaulis limicola HA5(T).

Sulfurifustis variabilis and Sulfuricaulis limicola are autotrophic sulfur-oxidizing bacteria belonging to the family Acidiferrobacteraceae in the order Acidiferrobacterales. The type strains of these species, strain skN76(T) and strain HA5(T), were isolated from lakes in Japan. Here we describe the complete genome sequences of Sulfurifustis variabilis skN76(T) and Sulfuricaulis limicola HA5(T). The genome of Sulfurifustis variabilis skN76(T) consists of one circular chromosome with size of 4.0 Mbp including 3864 protein-coding sequences. The genome of Sulfuricaulis limicola HA5(T) is 2.9 Mbp chromosome with 2763 protein-coding sequences. In both genomes, 46 transfer RNA-coding genes and one ribosomal RNA operon were identified. In the genomes, redundancies of the genes involved in sulfur oxidation and inorganic carbon fixation pathways were observed. This is the first report to show the complete genome sequences of bacteria belonging to the order Acidiferrobacterales in the class Gammaproteobacteria.


July 7, 2019

Genetic basis of priority effects: insights from nectar yeast.

Priority effects, in which the order of species arrival dictates community assembly, can have a major influence on species diversity, but the genetic basis of priority effects remains unknown. Here, we suggest that nitrogen scavenging genes previously considered responsible for starvation avoidance may drive priority effects by causing rapid resource depletion. Using single-molecule sequencing, we de novo assembled the genome of the nectar-colonizing yeast, Metschnikowia reukaufii, across eight scaffolds and complete mitochondrion, with gap-free coverage over gene spaces. We found a high rate of tandem gene duplication in this genome, enriched for nitrogen metabolism and transport. Both high-capacity amino acid importers, GAP1 and PUT4, present as tandem gene arrays, were highly expressed in synthetic nectar and regulated by the availability and quality of amino acids. In experiments with competitive nectar yeast, Candida rancensis, amino acid addition alleviated suppression of C. rancensis by early arrival of M. reukaufii, corroborating that amino acid scavenging may contribute to priority effects. Because niche pre-emption via rapid resource depletion may underlie priority effects in a broad range of microbial, plant and animal communities, nutrient scavenging genes like the ones we considered here may be broadly relevant to understanding priority effects.© 2016 The Author(s).


July 7, 2019

Comparative genomics of biotechnologically important yeasts.

Ascomycete yeasts are metabolically diverse, with great potential for biotechnology. Here, we report the comparative genome analysis of 29 taxonomically and biotechnologically important yeasts, including 16 newly sequenced. We identify a genetic code change, CUG-Ala, in Pachysolen tannophilus in the clade sister to the known CUG-Ser clade. Our well-resolved yeast phylogeny shows that some traits, such as methylotrophy, are restricted to single clades, whereas others, such as l-rhamnose utilization, have patchy phylogenetic distributions. Gene clusters, with variable organization and distribution, encode many pathways of interest. Genomics can predict some biochemical traits precisely, but the genomic basis of others, such as xylose utilization, remains unresolved. Our data also provide insight into early evolution of ascomycetes. We document the loss of H3K9me2/3 heterochromatin, the origin of ascomycete mating-type switching, and panascomycete synteny at the MAT locus. These data and analyses will facilitate the engineering of efficient biosynthetic and degradative pathways and gateways for genomic manipulation.


July 7, 2019

Complete genome sequence of Halomonas sp. R5-57.

The marine Arctic isolate Halomonas sp. R5-57 was sequenced as part of a bioprospecting project which aims to discover novel enzymes and organisms from low-temperature environments, with potential uses in biotechnological applications. Phenotypically, Halomonas sp. R5-57 exhibits high salt tolerance over a wide range of temperatures and has extra-cellular hydrolytic activities with several substrates, indicating it secretes enzymes which may function in high salinity conditions. Genome sequencing identified the genes involved in the biosynthesis of the osmoprotectant ectoine, which has applications in food processing and pharmacy, as well as those involved in production of polyhydroxyalkanoates, which can serve as precursors to bioplastics. The percentage identity of these biosynthetic genes from Halomonas sp. R5-57 and current production strains varies between 99 % for some to 69 % for others, thus it is plausible that R5-57 may have a different production capacity to currently used strains, or that in the case of PHAs, the properties of the final product may vary. Here we present the finished genome sequence (LN813019) of Halomonas sp. R5-57 which will facilitate exploitation of this bacterium; either as a whole-cell production host, or by recombinant expression of its individual enzymes.


July 7, 2019

Complete genome sequencing and comparative genomic analysis of the thermotolerant acetic acid bacterium, Acetobacter pasteurianus SKU1108, provide a new insight into thermotolerance.

Acetobacter pasteurianus SKU1108 is a typical thermotolerant acetic acid bacterium. In this study, the complete genome sequence of the SKU1108 strain was elucidated, and information on genomic modifications due to the thermal adaptation of SKU1108 was updated. In order to obtain a clearer understanding of the genetic background responsible for thermotolerance, the SKU1108 genome was compared with those of two closely related complete genome strains, thermotolerant A. pasteurianus 386B and mesophilic A. pasteurianus NBRC 3283. All 24 “thermotolerant genes” required for growth at higher temperatures in the thermotolerant Acetobacter tropicalis SKU1100 strain were conserved in all three strains. However, these thermotolerant genes accumulated amino acid mutations. Some biased mutations, particularly those that occurred in xanthine dehydrogenase XdhA, may be related to thermotolerance. By aligning whole genome sequences, we identified ten SKU1108 strain-specific regions, three of which were conserved in the genomes of the two thermotolerant A. pasteurianus strains. One of the regions contained a unique paralog of the thermotolerant gene xdhA, which may also be responsible for conferring thermotolerance. Thus, comparative genomics of complete genome sequences may provide novel insights into the phenotypes of these thermotolerant strains.


July 7, 2019

The complete genome sequence of the nicotine-degrading bacterium Shinella sp. HZN7.

Nicotine is a natural alkaloid that is very toxic to humans. To eliminate the harmful effects of nicotine in the environment, biological methods employing microbes to degrade nicotine are required (Brandsch, 2006; Liu et al., 2015). Shinella sp. HZN7 can degrade nicotine efficiently via the variant of a pyridine and pyrrolidine pathways (VPP; Ma et al., 2013; Qiu et al., 2014, 2015). The main intermediates in this pathway include 6-hydroxy-nicotine, 6-hydroxy-N-methylmyosmine, 6-hydroxypseudooxynicotine, 6-hydroxy-3-succinoyl-pyridine, and 2,5-dihydroxypyridine. This strain is the first nicotine-degrading bacterium to be isolated from the genus Shinella.


July 7, 2019

Comparative genomics reveals Lysinibacillus sphaericus group comprises a novel species.

Early in the 1990s, it was recognized that Lysinibacillus sphaericus, one of the most popular and effective entomopathogenic bacteria, was a highly heterogeneous group. Many authors have even proposed it comprises more than one species, but the lack of phenotypic traits that guarantee an accurate differentiation has not allowed this issue to be clarified. Now that genomic technologies are rapidly advancing, it is possible to address the problem from a whole genome perspective, getting insights into the phylogeny, evolutive history and biology itself.The genome of the Colombian strain L. sphaericus OT4b.49 was sequenced, assembled and annotated, obtaining 3 chromosomal contigs and no evidence of plasmids. Using these sequences and the 13 other L. sphaericus genomes available on the NCBI database, we carried out comparative genomic analyses that included whole genome alignments, searching for mobile elements, phylogenomic metrics (TETRA, ANI and in-silico DDH) and pan-genome assessments. The results support the hypothesis about this species as a very heterogeneous group. The entomopathogenic lineage is actually a single and independent species with 3728 core genes and 2153 accessory genes, whereas each non-toxic strain seems to be a separate species, though without a clear circumscription. Toxin-encoding genes, binA, B and mtx1, 2, 3 could be acquired via horizontal gene transfer in a single evolutionary event. The non-toxic strain OT4b.31 is the most related with the type strain KCTC 3346.The current L. sphaericus is actually a sensu lato due to a sub-estimation of diversity accrued using traditional non-genomics based classification strategies. The toxic lineage is the most studied with regards to its larvicidal activity, which is a greatly conserved trait among these strains and thus, their differentiating feature. Further studies are needed in order to establish a univocal classification of the non-toxic strains that, according to our results, seem to be a paraphyletic group.


July 7, 2019

Complete sequencing of plasmids containing blaOXA-163 and blaOXA-48 in Escherichia coli ST131.

OXA-48-like enzymes have emerged as important extended-spectrum ß-lactamases/carbapenemases in E. coli ST131. We report the structure of the first fully sequenced blaOXA-163 plasmid, and of two other blaOXA-48 plasmids in this lineage. blaOXA-163 was located on a 71kb IncN plasmid with other resistance genes. blaOXA-48 was present on IncL/M plasmids, genetically similar to other blaOXA-48 plasmid sequences, and consistent with inter-species/inter-lineage spread. The presence of blaOXA-48-like genes on epidemic plasmids in ST131 is of concern. Copyright © 2016, American Society for Microbiology. All Rights Reserved.


July 7, 2019

The evolution of orphan regions in genomes of a fungal pathogen of wheat.

Fungal plant pathogens rapidly evolve virulence on resistant hosts through mutations in genes encoding proteins that modulate the host immune responses. The mutational spectrum likely includes chromosomal rearrangements responsible for gains or losses of entire genes. However, the mechanisms creating adaptive structural variation in fungal pathogen populations are poorly understood. We used complete genome assemblies to quantify structural variants segregating in the highly polymorphic fungal wheat pathogen Zymoseptoria tritici The genetic basis of virulence in Z. tritici is complex, and populations harbor significant genetic variation for virulence; hence, we aimed to identify whether structural variation led to functional differences. We combined single-molecule real-time sequencing, genetic maps, and transcriptomics data to generate a fully assembled and annotated genome of the highly virulent field isolate 3D7. Comparative genomics analyses against the complete reference genome IPO323 identified large chromosomal inversions and the complete gain or loss of transposable-element clusters, explaining the extensive chromosomal-length polymorphisms found in this species. Both the 3D7 and IPO323 genomes harbored long tracts of sequences exclusive to one of the two genomes. These orphan regions contained 296 genes unique to the 3D7 genome and not previously known for this species. These orphan genes tended to be organized in clusters and showed evidence of mutational decay. Moreover, the orphan genes were enriched in genes encoding putative effectors and included a gene that is one of the most upregulated putative effector genes during wheat infection. Our study showed that this pathogen species harbored extensive chromosomal structure polymorphism that may drive the evolution of virulence.Pathogen outbreak populations often harbor previously unknown genes conferring virulence. Hence, a key puzzle of rapid pathogen evolution is the origin of such evolutionary novelty in genomes. Chromosomal rearrangements and structural variation in pathogen populations likely play a key role. However, identifying such polymorphism is challenging, as most genome-sequencing approaches only yield information about point mutations. We combined long-read technology and genetic maps to assemble the complete genome of a strain of a highly polymorphic fungal pathogen of wheat. Comparisons against the reference genome of the species showed substantial variation in the chromosome structure and revealed large regions unique to each assembled genome. These regions were enriched in genes encoding likely effector proteins, which are important components of pathogenicity. Our study showed that pathogen populations harbor extensive polymorphism at the chromosome level and that this polymorphism can be a source of adaptive genetic variation in pathogen evolution. Copyright © 2016 Plissonneau et al.


July 7, 2019

Genomic recombination leading to decreased virulence of group B Streptococcus in a mouse model of adult invasive disease.

Adult invasive disease caused by Group B Streptococcus (GBS) is increasing worldwide. Whole-genome sequencing (WGS) now permits rapid identification of recombination events, a phenomenon that occurs frequently in GBS. Using WGS, we described that strain NGBS375, a capsular serotype V GBS isolate of sequence type (ST)297, has an ST1 genomic background but has acquired approximately 300 kbp of genetic material likely from an ST17 strain. Here, we examined the virulence of this strain in an in vivo model of GBS adult invasive infection. The mosaic ST297 strain showed intermediate virulence, causing significantly less systemic infection and reduced mortality than a more virulent, serotype V ST1 isolate. Bacteremia induced by the ST297 strain was similar to that induced by a serotype III ST17 strain, which was the least virulent under the conditions tested. Yet, under normalized bacteremia levels, the in vivo intrinsic capacity to induce the production of pro-inflammatory cytokines was similar between the ST297 strain and the virulent ST1 strain. Thus, the diminished virulence of the mosaic strain may be due to reduced capacity to disseminate or multiply in blood during a systemic infection which could be mediated by regulatory factors contained in the recombined region.


July 7, 2019

An improved high-quality draft genome sequence of Carnobacterium inhibens subsp. inhibens strain K1(T).

Despite their ubiquity and their involvement in food spoilage, the genus Carnobacterium remains rather sparsely characterized at the genome level. Carnobacterium inhibens K1(T) is a member of the Carnobacteriaceae family within the class Bacilli. This strain is a Gram-positive, rod-shaped bacterium isolated from the intestine of an Atlantic salmon. The present study determined the genome sequence and annotation of Carnobacterium inhibens K1(T). The genome comprised 2,748,608 bp with a G?+?C content of 34.85 %, which included 2621 protein-coding genes and 116 RNA genes. The strain contained five contigs corresponding to presumptive plasmids of sizes: 19,036; 24,250; 26,581; 65,272; and 65,904 bp.


July 7, 2019

Novel methyltransferase recognition motif identified in Chania multitudinisentens RB-25(T) gen. nov., sp. nov.

DNA methylation, defined by the addition of a methyl group to adenine or cytosine bases in DNA catalyzed by DNA methyltransferases (MTases), is one of the most studied post-replicative DNA modification mechanism in bacteria (Roberts et al., 2003b). The three forms of nucleotide methylation identified to date are: N6-methyladenine(m6A), N4-methylcytosine (m4C), and 5-methylcytosine (m5C) (Gromova and Khoroshaev, 2003).


July 7, 2019

A full-body transcriptome and proteome resource for the European common carp.

The common carp (Cyprinus carpio) is the oldest, most domesticated and one of the most cultured fish species for food consumption. Besides its economic importance, the common carp is also highly suitable for comparative physiological and disease studies in combination with the animal model zebrafish (Danio rerio). They are genetically closely related but offer complementary benefits for fundamental research, with the large body mass of common carp presenting possibilities for obtaining sufficient cell material for advanced transcriptome and proteome studies.Here we have used 19 different tissues from an F1 hybrid strain of the common carp to perform transcriptome analyses using RNA-Seq. For a subset of the tissues we also have performed deep proteomic studies. As a reference, we updated the European common carp genome assembly using low coverage Pacific Biosciences sequencing to permit high-quality gene annotation. These annotated gene lists were linked to zebrafish homologs, enabling direct comparisons with published datasets. Using clustering, we have identified sets of genes that are potential selective markers for various types of tissues. In addition, we provide a script for a schematic anatomical viewer for visualizing organ-specific expression data.The identified transcriptome and proteome data for carp tissues represent a useful resource for further translational studies of tissue-specific markers for this economically important fish species that can lead to new markers for organ development. The similarity to zebrafish expression patterns confirms the value of common carp as a resource for studying tissue-specific expression in cyprinid fish. The availability of the annotated gene set of common carp will enable further research with both applied and fundamental purposes.


July 7, 2019

Diversity of the tetracycline mobilome within a Chinese pig manure sample.

Tetracycline antibiotics are widely used in livestock, and tetracycline resistance genes (TRG) are frequently reported in the manure of farmed animals. However, the diversity of TRG-carrying transposons in manure has still been rarely investigated. Using a culture-free functional metagenomic procedure, combined with large-insert library construction and sequencing, bioinformatic analyses, and functional experiments, we identified 17 distinct TRGs in a single pig manure sample, including two new tet genes: tet(59), encoding a tetracycline efflux pump, and tet(W/N/W), encoding mosaic ribosomal protection. Our study also revealed six new TRG-carrying putative nonconjugative transposons: Tn5706-like transposon Tn6298, IS200/605-related transposon Tn6303, Tn3 family transposon Tn6299, and three ISCR2-related transposons, Tn62300, Tn62301, and Tn62302 IMPORTANCE: Fertilization of agricultural fields with animal manure is believed to play a major role in antibiotic resistance dissemination in the environment. There is growing concern for the possible spread of antibiotic resistance from the environment to humans since genetic resistance determinants may be located in transposons and other mobile genetic elements potentially transferable to pathogens. Among the various antibiotic resistance genes found in manure, tetracycline resistance genes (TRGs) are some of the most common. The present study provides a detailed snapshot of the tetracycline mobilome in a single pig manure sample, revealing an unappreciated diversity of TRGs and potential TRG mobility vectors. Our precise identification of the TRG-carrying units will enable us to investigate in more details their mobility effectiveness. Copyright © 2016, American Society for Microbiology. All Rights Reserved.


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