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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.

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July 7, 2019

Complete genome sequence of Agarivorans gilvus WH0801(T), an agarase-producing bacterium isolated from seaweed.

Agarivorans gilvus WH0801(T), an agarase-producing bacterium, was isolated from the surface of seaweed. Here, we present the complete genome sequence, which consists of one circular chromosome of 4,416,600bp with a GC content of 45.9%. This genetic information will provide insight into biotechnological applications of producing agar for food and industry. Copyright © 2015 Elsevier B.V. All rights reserved.

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July 7, 2019

Long read and single molecule DNA sequencing simplifies genome assembly and TAL effector gene analysis of Xanthomonas translucens.

The species Xanthomonas translucens encompasses a complex of bacterial strains that cause diseases and yield loss on grass species including important cereal crops. Three pathovars, X. translucens pv. undulosa, X. translucens pv. translucens and X. translucens pv.cerealis, have been described as pathogens of wheat, barley, and oats. However, no complete genome sequence for a strain of this complex is currently available.A complete genome sequence of X. translucens pv. undulosa strain XT4699 was obtained by using PacBio long read, single molecule, real time (SMRT) DNA sequences and Illumina sequences. Draft genome sequences of nineteen additional X. translucens strains, which were collected from wheat or barley in different regions and at different times, were generated by Illumina sequencing. Phylogenetic relationships among different Xanthomonas strains indicates that X. translucens are members of a distinct clade from so-called group 2 xanthomonads and three pathovars of this species, undulosa, translucens and cerealis, represent distinct subclades in the group 1 clade. Knockout mutation of type III secretion system of XT4699 eliminated the ability to cause water-soaking symptoms on wheat and barley and resulted in a reduction in populations on wheat in comparison to the wild type strain. Sequence comparison of X. translucens strains revealed the genetic variation on type III effector repertories among different pathovars or within one pathovar. The full genome sequence of XT4699 reveals the presence of eight members of the Transcription-Activator Like (TAL) effector genes, which are phylogenetically distant from previous known TAL effector genes of group 2 xanthomonads. Microarray and qRT-PCR analyses revealed TAL effector-specific wheat gene expression modulation.PacBio long read sequencing facilitates the assembly of Xanthomonas genomes and the multiple TAL effector genes, which are difficult to assemble from short read platforms. The complete genome sequence of X. translucens pv. undulosa strain XT4699 and draft genome sequences of nineteen additional X. translucens strains provides a resource for further genetic analyses of pathogenic diversity and host range of the X. translucens species complex. TAL effectors of XT4699 strain play roles in modulating wheat host gene expressions.

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July 7, 2019

In planta comparative transcriptomics of host-adapted strains of Ralstonia solanacearum.

Background. Ralstonia solanacearum is an economically important plant pathogen with an unusually large host range. The Moko (banana) and NPB (not pathogenic to banana) strain groups are closely related but are adapted to distinct hosts. Previous comparative genomics studies uncovered very few differences that could account for the host range difference between these pathotypes. To better understand the basis of this host specificity, we used RNAseq to profile the transcriptomes of an R. solanacearum Moko strain and an NPB strain under in vitro and in planta conditions. Results. RNAs were sequenced from bacteria grown in rich and minimal media, and from bacteria extracted from mid-stage infected tomato, banana and melon plants. We computed differential expression between each pair of conditions to identify constitutive and host-specific gene expression differences between Moko and NPB. We found that type III secreted effectors were globally up-regulated upon plant cell contact in the NPB strain compared with the Moko strain. Genes encoding siderophore biosynthesis and nitrogen assimilation genes were highly up-regulated in the NPB strain during melon pathogenesis, while denitrification genes were up-regulated in the Moko strain during banana pathogenesis. The relatively lower expression of oxidases and the denitrification pathway during banana pathogenesis suggests that R. solanacearum experiences higher oxygen levels in banana pseudostems than in tomato or melon xylem. Conclusions. This study provides the first report of differential gene expression associated with host range variation. Despite minimal genomic divergence, the pathogenesis of Moko and NPB strains is characterized by striking differences in expression of virulence- and metabolism-related genes.

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July 7, 2019

Genomic and metagenomic analysis of microbes in a soil environment affected by the 2011 Great East Japan Earthquake tsunami.

The Great East Japan Earthquake of 2011 triggered large tsunami waves, which flooded broad areas of land along the Pacific coast of eastern Japan and changed the soil environment drastically. However, the microbial characteristics of tsunami-affected soil at the genomic level remain largely unknown. In this study, we isolated microbes from a soil sample using general low-nutrient and seawater-based media to investigate microbial characteristics in tsunami-affected soil.As expected, a greater proportion of strains isolated from the tsunami-affected soil than the unaffected soil grew in the seawater-based medium. Cultivable strains in both the general low-nutrient and seawater-based media were distributed in the genus Arthrobacter. Most importantly, whole-genome sequencing of four of the isolated Arthrobacter strains revealed independent losses of siderophore-synthesis genes from their genomes. Siderophores are low-molecular-weight, iron-chelating compounds that are secreted for iron uptake; thus, the loss of siderophore-synthesis genes indicates that these strains have adapted to environments with high-iron concentrations. Indeed, chemical analysis confirmed the investigated soil samples to be rich in iron, and culture experiments confirmed weak cultivability of some of these strains in iron-limited media. Furthermore, metagenomic analyses demonstrated over-representation of denitrification-related genes in the tsunami-affected soil sample, as well as the presence of pathogenic and marine-living genera and genes related to salt-tolerance.Collectively, the present results would provide an example of microbial characteristics of soil disturbed by the tsunami, which may give an insight into microbial adaptation to drastic environmental changes. Further analyses on microbial ecology after a tsunami are envisioned to develop a deeper understanding of the recovery processes of terrestrial microbial ecosystems.

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July 7, 2019

Complete genome sequence and genomic characterization of Microcystis panniformis FACHB 1757 by third-generation sequencing.

The cyanobacterial genus Microcystis is well known as the main group that forms harmful blooms in water. A strain of Microcystis, M. panniformis FACHB1757, was isolated from Meiliang Bay of Lake Taihu in August 2011. The whole genome was sequenced using PacBio RS II sequencer with 48-fold coverage. The complete genome sequence with no gaps contained a 5,686,839 bp chromosome and a 38,683 bp plasmid, which coded for 6,519 and 49 proteins, respectively. Comparison with strains of M. aeruginosa and some other water bloom-forming cyanobacterial species revealed large-scale structure rearrangement and length variation at the genome level along with 36 genomic islands annotated genome-wide, which demonstrates high plasticity of the M. panniformis FACHB1757 genome and reveals that Microcystis has a flexible genome evolution.

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July 7, 2019

A highly arginolytic Streptococcus species that potently antagonizes Streptococcus mutans.

The ability of certain oral biofilm bacteria to moderate pH through arginine metabolism by the arginine deiminase system (ADS) is a deterrent to the development of dental caries. Here, we characterize a novel Streptococcus strain, designated strain A12, isolated from supragingival dental plaque of a caries-free individual. A12 not only expressed the ADS pathway at high levels under a variety of conditions but also effectively inhibited growth and two intercellular signaling pathways of the dental caries pathogen Streptococcus mutans. A12 produced copious amounts of H2O2 via the pyruvate oxidase enzyme that were sufficient to arrest the growth of S. mutans. A12 also produced a protease similar to challisin (Sgc) of Streptococcus gordonii that was able to block the competence-stimulating peptide (CSP)-ComDE signaling system, which is essential for bacteriocin production by S. mutans. Wild-type A12, but not an sgc mutant derivative, could protect the sensitive indicator strain Streptococcus sanguinis SK150 from killing by the bacteriocins of S. mutans. A12, but not S. gordonii, could also block the XIP (comX-inducing peptide) signaling pathway, which is the proximal regulator of genetic competence in S. mutans, but Sgc was not required for this activity. The complete genome sequence of A12 was determined, and phylogenomic analyses compared A12 to streptococcal reference genomes. A12 was most similar to Streptococcus australis and Streptococcus parasanguinis but sufficiently different that it may represent a new species. A12-like organisms may play crucial roles in the promotion of stable, health-associated oral biofilm communities by moderating plaque pH and interfering with the growth and virulence of caries pathogens. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

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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.

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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.

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July 7, 2019

Genome sequence of Shimia str. SK013, a representative of the Roseobacter group isolated from marine sediment.

Shimia strain SK013 is an aerobic, Gram-negative, rod shaped alphaproteobacterium affiliated with the Roseobacter group within the family Rhodobacteraceae. The strain was isolated from surface sediment (0-1 cm) of the Skagerrak at 114 m below sea level. The 4,049,808 bp genome of Shimia str. SK013 comprises 3,981 protein-coding genes and 47 RNA genes. It contains one chromosome and no extrachromosomal elements. The genome analysis revealed the presence of genes for a dimethylsulfoniopropionate lyase, demethylase and the trimethylamine methyltransferase (mttB) as well as genes for nitrate, nitrite and dimethyl sulfoxide reduction. This indicates that Shimia str. SK013 is able to switch from aerobic to anaerobic metabolism and thus is capable of aerobic and anaerobic sulfur cycling at the seafloor. Among the ability to convert other sulfur compounds it has the genetic capacity to produce climatically active dimethyl sulfide. Growth on glutamate as a sole carbon source results in formation of cell-connecting filaments, a putative phenotypic adaptation of the surface-associated strain to the environmental conditions at the seafloor. Genome analysis revealed the presence of a flagellum (fla1) and a type IV pilus biogenesis, which is speculated to be a prerequisite for biofilm formation. This is also related to genes responsible for signalling such as N-acyl homoserine lactones, as well as quip-genes responsible for quorum quenching and antibiotic biosynthesis. Pairwise similarities of 16S rRNA genes (98.56 % sequence similarity to the next relative S. haliotis) and the in silico DNA-DNA hybridization (21.20 % sequence similarity to S. haliotis) indicated Shimia str. SK013 to be considered as a new species. The genome analysis of Shimia str. SK013 offered first insights into specific physiological and phenotypic adaptation mechanisms of Roseobacter-affiliated bacteria to the benthic environment.

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July 7, 2019

The identification of novel diagnostic marker genes for the detection of beer spoiling Pediococcus damnosus strains using the BlAst Diagnostic Gene findEr.

As the number of bacterial genomes increases dramatically, the demand for easy to use tools with transparent functionality and comprehensible output for applied comparative genomics grows as well. We present BlAst Diagnostic Gene findEr (BADGE), a tool for the rapid prediction of diagnostic marker genes (DMGs) for the differentiation of bacterial groups (e.g. pathogenic / nonpathogenic). DMG identification settings can be modified easily and installing and running BADGE does not require specific bioinformatics skills. During the BADGE run the user is informed step by step about the DMG finding process, thus making it easy to evaluate the impact of chosen settings and options. On the basis of an example with relevance for beer brewing, being one of the oldest biotechnological processes known, we show a straightforward procedure, from phenotyping, genome sequencing, assembly and annotation, up to a discriminant marker gene PCR assay, making comparative genomics a means to an end. The value and the functionality of BADGE were thoroughly examined, resulting in the successful identification and validation of an outstanding novel DMG (fabZ) for the discrimination of harmless and harmful contaminations of Pediococcus damnosus, which can be applied for spoilage risk determination in breweries. Concomitantly, we present and compare five complete P. damnosus genomes sequenced in this study, finding that the ability to produce the unwanted, spoilage associated off-flavor diacetyl is a plasmid encoded trait in this important beer spoiling species.

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July 7, 2019

Complete genome sequence of Acinetobacter sp. TTH0-4, a cold-active crude oil degrading strain isolated from Qinghai-Tibet Plateau.

Acinetobacter sp. strain TTH0-4 was isolated from a permafrost region in Qinghai-Tibet Plateau. With its capability to degrade crude oil at low temperature, 10°C, the strain could be an excellent candidate for the bioremediation of crude oil pollution in cold areas or at cold seasons. We sequenced and annotated the whole genome to serve as a basis for further elucidation of the genetic background of this promising strain, and provide opportunities for investigating the metabolic and regulatory mechanisms and optimizing the biodegradative activity in cold environment. Copyright © 2016. Published by Elsevier B.V.

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July 7, 2019

Complete genome sequence of thiosulfate-oxidizing Bosea sp. strain PAMC26642 isolated from an Arctic lichen.

Thiosulfate-oxidizing Bosea sp. strain PAMC26642 was isolated from the Arctic lichen Stereocaulon sp. Complete genome sequencing of Bosea sp. PAMC26642 revealed several genes involved in thiosulfate oxidation. An analysis of the Bosea sp. PAMC26642 genome will provide novel insight into the genetic basis of its physiology and enable further analysis of key genes in the thiosulfate oxidation pathway. Copyright © 2016 Elsevier B.V. All rights reserved.

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