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July 7, 2019

Characterization of a new chlorovirus type with permissive and non-permissive features on phylogenetically related algal strains.

A previous report indicated that prototype chlorovirus PBCV-1 replicated in two Chlorella variabilis algal strains, NC64A and Syngen 2-3, that are ex-endosymbionts isolated from the protozoan Paramecium bursaria. Surprisingly, plaque-forming viruses on Syngen 2-3 lawns were often higher than on NC64A lawns from indigenous water samples. These differences led to the discovery of viruses that exclusively replicate in Syngen 2-3 cells, named Only Syngen (OSy) viruses. OSy-NE5, the prototype virus for the proposed new species, had a linear dsDNA genome of 327kb with 44-nucleotide-long, incompletely base-paired, covalently closed hairpin ends. Each hairpin structure was followed by an identical 2612 base-paired inverted sequence after which the DNA sequence diverged. OSy-NE5 encoded 357 predicted CDSs and 13 tRNAs. Interestingly, OSy-NE5 attached to and initiated infection in NC64A cells but infectious progeny viruses were not produced; thus OSy-NE5 replication in NC64A is blocked at some later stage of replication. Copyright © 2016 Elsevier Inc. All rights reserved.

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July 7, 2019

Complete genome sequence of Lactobacillus plantarum LZ206, a potential probiotic strain with antimicrobial activity against food-borne pathogenic microorganisms.

Lactobacilli strains have been considered as important candidates for manufacturing “natural food”, due to their antimicrobial properties and generally regarded as safe (GRAS) status. Lactobacillus plantarum LZ206 is a potential probiotic strain isolated from raw cow milk, with antimicrobial activity against various pathogens, including Gram-positive bacteria (Staphylococcus aureus and Listeria monocytogenes), Gram-negtive bacteria (Escherichia coli and Salmonella enterica), and fungus Candida albicans. To better understand molecular base for its antimicrobial activity, entire genome of LZ206 was sequenced. It was revealed that genome of LZ206 contained a circular 3,212,951-bp chromosome, two circular plasmids and one predicted linear plasmid. A plantaricin gene cluster, which is responsible for bacteriocins biosynthesis and could be associated with its broad-spectrum antimicrobial activity, was identified based on comparative genomic analysis. Whole genome sequencing of L. plantarum LZ206 might facilitate its applications to protect food products from pathogens’ contamination in the dairy industry. Copyright © 2016 Elsevier B.V. All rights reserved.

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July 7, 2019

Iteratively improving natamycin production in Streptomyces gilvosporeus by a large operon-reporter based strategy

Many high-value secondary metabolites are assembled by very large multifunctional polyketide synthases or non-ribosomal peptide synthetases encoded by giant genes, for instance, natamycin production in an industrial strain of Streptomyces gilvosporeus. In this study, a large operon reporter-based selection system has been developed using the selectable marker gene neo to report the expression both of the large polyketide synthase genes and of the entire gene cluster, thereby facilitating the selection of natamycin-overproducing mutants by iterative random mutagenesis breeding. In three successive rounds of mutagenesis and selection, the natamycin titer was increased by 110%, 230%, and 340%, respectively, and the expression of the whole biosynthetic gene cluster was correspondingly increased. An additional copy of the natamycin gene cluster was found in one overproducer. These findings support the large operon reporter-based selection system as a useful tool for the improvement of industrial strains utilized in the production of polyketides and non-ribosomal peptides. Copyright © 2016 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.

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July 7, 2019

Complete genome sequences of four different Bordetella sp. isolates causing human respiratory infections.

Species of the genus Bordetella associate with various animal hosts, frequently causing respiratory disease. Bordetella pertussis is the primary agent of whooping cough and other Bordetella species can cause similar cough illness. Here, we report four complete genome sequences from isolates of different Bordetella species recovered from human respiratory infections. Copyright © 2016 Weigand et al.

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July 7, 2019

The complete genome of Dietzia timorensis ID05-A0528(T) revealed the genetic basis for its saline-alkali tolerance.

The type strain Dietzia timorensis ID05-A0528(T), was reported to be able to survive in the highly saline and alkaline environments with diverse carbon sources. In order to more pertinently understand the genetic mechanisms of its environmental tolerance and crude oil emulsification, we reported the complete genome sequence of the strain in the study. The genome contains only one circular chromosome, with the total size of 3,607,892 bps, and the G+C content of this strain is 65.58%, much lower than other type strains of this genus. It was found that strain ID05-A0528(T) contains genes involved in transportation and biosynthesis of compatible solutes, as well as genes encoding monovalent cation/proton antiporters, which could explain its abilities to tolerate high salinity and alkalinity. Various central metabolic routes and complete alkane hydroxylation pathway were also identified in the genome of strain ID05-A0528(T), which is in accordance with its ability to use a wide spectrum of carbon sources and to degrade n-alkanes. Copyright © 2016. Published by Elsevier B.V.

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July 7, 2019

Comprehensive genomic and phenotypic metal resistance profile of Pseudomonas putida strain S13.1.2 isolated from a vineyard soil.

Trace metals are required in many cellular processes in bacteria but also induce toxic effects to cells when present in excess. As such, various forms of adaptive responses towards extracellular trace metal ions are essential for the survival and fitness of bacteria in their environment. A soil Pseudomonas putida, strain S13.1.2 has been isolated from French vineyard soil samples, and shown to confer resistance to copper ions. Further investigation revealed a high capacity to tolerate elevated concentrations of various heavy metals including nickel, cobalt, cadmium, zinc and arsenic. The complete genome analysis was conducted using single-molecule real-time (SMRT) sequencing and the genome consisted in a single chromosome at the size of 6.6 Mb. Presence of operons and gene clusters such as cop, cus, czc, nik, and asc systems were detected and accounted for the observed resistance phenotypes. The unique features in terms of specificity and arrangements of some genetic determinants were also highlighted in the study. Our findings has provided insights into the adaptation of this strain to accumulation and persistence of copper and other heavy metals in vineyard soil environment.

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July 7, 2019

Thermococcus piezophilus sp. nov., a novel hyperthermophilic and piezophilic archaeon with a broad pressure range for growth, isolated from a deepest hydrothermal vent at the Mid-Cayman Rise.

A novel strictly anaerobic, hyperthermophilic archaeon, designated strain CDGS(T), was isolated from a deep-sea hydrothermal vent in the Cayman Trough at 4964m water depth. The novel isolate is obligate anaerobe and grows chemoorganoheterotrophically with stimulation of growth by sulphur containing compounds. Its growth is optimal at 75°C, pH 6.0 and under a pressure of 50MPa. It possesses the broadest hydrostatic pressure range for growth that has ever been described for a microorganism. Its genomic DNA G+C content is 51.11 mol%. The novel isolate belongs to the genus Thermococcus. Phylogenetic analyses indicated that it is most closely related to Thermococcus barossii DSM17882(T) based on its 16S rRNA gene sequence, and to ‘Thermococcus onnurineus’ NA1 based on its whole genome sequence. The average nucleotide identity scores with these strains are 77.66% for T. barossii and 84.84% for ‘T. onnurineus’, respectively. Based on the draft whole genome sequence and phenotypic characteristics, strain CDGS(T) is suggested to be separated into a novel species within the genus Thermococcus, with proposed name Thermococcus piezophilus (type strain CDGS(T)=ATCC TSD-33(T)=UBOCC 3296(T)). Copyright © 2016 Elsevier GmbH. All rights reserved.

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July 7, 2019

Complete genome sequence of a bacterium representing a deep uncultivated lineage within the Gammaproteobacteria associated with the degradation of polycyclic aromatic hydrocarbons.

The bacterial strain TR3.2, representing a novel deeply branching lineage within the Gammaproteobacteria, was isolated and its genome sequenced. This isolate is the first cultivated representative of the previously described “Pyrene Group 2” (PG2) and represents a variety of environmental sequences primarily associated with petrochemical contamination and aromatic hydrocarbon degradation. Copyright © 2016 Singleton et al.

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July 7, 2019

Complete genome sequence of Mycobacterium ulcerans subsp. shinshuense.

Mycobacterium ulcerans subsp. shinshuense produces mycolactone and causes Buruli ulcer. Here, we report the complete sequence of its genome, which comprises a 5.9-Mb chromosome and a 166-kb plasmid (pShT-P). The sequence will represent the essential data for future phylogenetic and comparative genome studies of mycolactone-producing mycobacteria. Copyright © 2016 Yoshida et al.

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July 7, 2019

Silicon content of individual cells of Synechococcus from the North Atlantic Ocean

The widely distributed marine cyanobacterium Synechococcus is thought to exert an influence on the marine silicon (Si) cycle through its high cellular Si relative to organic content. There are few measurements of Si in natural populations of Synechococcus, however, and the degree to which Synechococcus from various oligotrophic field sites and depths accumulate the element is unknown. We used synchrotron x-ray fluorescence to measure Si quotas in individual Synechococcus cells collected during three cruises in the western North Atlantic Ocean in the summer and fall, focusing on cells from the surface mixed layer (SML; <10 m) and the deep chlorophyll maximum (DCM). Individual cell quotas varied widely, from 1 to 4700 amol Si cell- 1, though the middle 50% of quotas ranged between 17 and 119 amol Si cell- 1. Mean station-specific quotas exhibited an even narrower range of 31–72 amol Si cell- 1. No significant differences in Si quotas were observed across cruises or among stations, and no effect of ambient silicic acid concentration on quotas was observed within the narrow range of silicic acid concentrations encountered (0.6–1.3 µM). Despite this small range in ambient silicic acid, cells collected from the SML had an average of two-fold more Si than cells collected from the DCM. Differences in Si content with depth may be related to observed differences in the dominant Synechococcus clades between the SML and DCM habitats, determined by petB gene sequencing.

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July 7, 2019

Genome sequence of the photoarsenotrophic bacterium Ectothiorhodospira sp. strain BSL-9, isolated from a hypersaline alkaline arsenic-rich extreme environment.

The full genome sequence of Ectothiorhodospira sp. strain BSL-9 is reported here. This purple sulfur bacterium encodes an arxA-type arsenite oxidase within the arxB2AB1CD gene island and is capable of carrying out “photoarsenotrophy” anoxygenic photosynthetic arsenite oxidation. Its genome is composed of 3.5 Mb and has approximately 63% G+C content. Copyright © 2016 Hernandez-Maldonado et al.

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July 7, 2019

Contiguous and accurate de novo assembly of metazoan genomes with modest long read coverage.

Genome assemblies that are accurate, complete and contiguous are essential for identifying important structural and functional elements of genomes and for identifying genetic variation. Nevertheless, most recent genome assemblies remain incomplete and fragmented. While long molecule sequencing promises to deliver more complete genome assemblies with fewer gaps, concerns about error rates, low yields, stringent DNA requirements and uncertainty about best practices may discourage many investigators from adopting this technology. Here, in conjunction with the platinum standard Drosophila melanogaster reference genome, we analyze recently published long molecule sequencing data to identify what governs completeness and contiguity of genome assemblies. We also present a hybrid meta-assembly approach that achieves remarkable assembly contiguity for both Drosophila and human assemblies with only modest long molecule sequencing coverage. Our results motivate a set of preliminary best practices for obtaining accurate and contiguous assemblies, a ‘missing manual’ that guides key decisions in building high quality de novo genome assemblies, from DNA isolation to polishing the assembly.© The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

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July 7, 2019

Comparative genomics and physiology of the butyrate-producing bacterium Intestinimonas butyriciproducens.

Intestinimonas is a newly described bacterial genus with representative strains present in the intestinal tract of human and other animals. Despite unique metabolic features including the production of butyrate from both sugars and amino acids, there is to date no data on their diversity, ecology, and physiology. Using a comprehensive phylogenetic approach, Intestinimomas was found to include at least three species that colonize primarily the human and mouse intestine. We focused on the most common and cultivable species of the genus, Intestinimonas butyriciproducens, and performed detailed genomic and physiological comparison of strains SRB521(T) and AF211, isolated from the mouse and human gut respectively. The complete 3.3-Mb genomic sequences of both strains were highly similar with 98.8% average nucleotide identity, testifying to their assignment to one single species. However, thorough analysis revealed significant genomic rearrangements, variations in phage-derived sequences, and the presence of new CRISPR sequences in both strains. Moreover, strain AF211 appeared to be more efficient than strain SRB521(T) in the conversion of the sugars arabinose and galactose. In conclusion, this study provides genomic and physiological insight into Intestinimonas butyriciproducens, a prevalent butyrate-producing species, differentiating strains that originate from the mouse and human gut.© 2016 The Authors. Environmental Microbiology Reports published by Society for Applied Microbiology and JohnWiley & Sons Ltd.

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