Genomic GC Research Articles

Sex without crossing over in the yeast Saccharomycodes ludwigii

BackgroundIntermixing of genomes through meiotic reassortment and recombination of homologous chromosomes is a unifying theme of sexual reproduction in eukaryotic organisms and is considered crucial for their adaptive evolution. Previous studies of the budding yeast species Saccharomycodes ludwigii suggested that meiotic crossing over might be absent from its sexual life cycle, which is predominated by fertilization within the meiotic tetrad.ResultsWe demonstrate that recombination is extremely suppressed during meiosis in Sd. ludwigii. DNA double-strand break formation by the conserved transesterase Spo11, processing and repair involving interhomolog interactions are required for normal meiosis but do not lead to crossing over. Although the species has retained an intact meiotic gene repertoire, genetic and population analyses suggest the exceptionally rare occurrence of meiotic crossovers in its genome. A strong AT bias of spontaneous mutations and the absence of recombination are likely responsible for its unusually low genomic GC level.ConclusionsSd. ludwigii has followed a unique evolutionary trajectory that possibly derives fitness benefits from the combination of frequent mating between products of the same meiotic event with the extreme suppression of meiotic recombination. This life style ensures preservation of heterozygosity throughout its genome and may enable the species to adapt to its environment and survive with only minimal levels of rare meiotic recombination. We propose Sd. ludwigii as an excellent natural forum for the study of genome evolution and recombination rates.

Identification and genome analysis of a novel picornavirus from captive belugas (Delphinapterus leucas) in China

The discovery of new viruses is important for predicting their potential threats to the health of humans and other animals. A novel picornavirus was identified from oral, throat, and anal swab samples collected from belugas (Delphinapterus leucas), from Dalian Sun Asia Tourism Holding Co., China, between January and December 2018, using a metagenomics approach. The genome of this novel PicoV-HMU-1 strain was 8197 nucleotides (nt) in length, with a open reading frame (from 1091 to 8074 nt) that encoded a polyprotein precursor of 2328 amino acids. Moreover, the genomic length and GC content of PicoV-HMU-1 were within the ranges found in other picornaviruses, and the genome organization was also similar. Nevertheless, PicoV-HMU-1 had a lower amino acid identity and distinct host species compared with other members of the Picornaviridae family. Phylogenetic trees were constructed based on the P1 and 3D amino acid sequences of PicoV-HMU-1 along with representative members of the Picornaviridae family, which showed that PicoV-HMU-1 was related to unclassified bat picornaviruses groups. These findings suggest that the PicoV-HMU-1 strain represents a potentially novel genus of picornavirus. These data can enhance our understanding of the picornavirus genetic diversity and evolution.

Actinomyces capricornis sp. nov., isolated from the oral cavity of a Japanese serow.

A novel Gram-positive, facultatively anaerobic, rod-shaped, nonspore forming, nonmotile organism was isolated from a Japanese serow oral cavity. Designated strain MAS-1T , it is most closely related to Actinomyces bowdenii DSM 15435T , with which it shares 98.07% sequence homology in the 16S ribosomal RNA gene. The primarily detected cellular fatty acids in strain MAS-1T were C16:0 and C18:1 w9c. The predominant respiratory quinone was MK-9 (H4 ). The major polar lipids were phosphatidylcholines, phosphatidylinositols, and glycophospholipids. The genomic DNA GC content of the isolate was 71.3 mol%. The digital DNA-DNA hybridization and average nucleotide identity values between MAS-1T and its related species were 23.5%-39.5% and 82.11%-91.01%, respectively, which were below the threshold (70% and 95%, respectively) for species delineation, indicating that strain MAS-1T represents a novel species. Strain MAS-1T can be differentiated from A. bowdenii by their reactions to naphthol-AS-BI-phosphohydrolase, α-galactosidase, β-galactosidase, and N-acetyl-β-glucosaminidase, as well as differing acid production from glycogen. Based on the results of genotypic, phenotypic, and biochemical analyses, herein it is proposed that the identified bacteria can be classified as a novel species, Actinomyces capricornis sp. nov., strain MAS-1T (=JCM 34236T = DSM 111732T ).

BactoTraits – A functional trait database to evaluate how natural and man-induced changes influence the assembly of bacterial communities

In the environment, abiotic (climatic conditions, physico-chemical parameters), biotic (interactions between microorganisms, vegetation and fauna), and anthropogenic (stress, pollution) filters are driving the microbial diversity observed locally. A key question in microbial ecology is to understand the impact of these filters on bacterial diversity and ecosystem functioning. To highlight the responses of bacterial assemblages to these ecological filters, a new approach based on bacterial functional traits has been developed. This approach provides a functional picture of bacterial assemblages using morphological, physiological, and genomic traits as proxies of functions, and leads to a generalizable approach over a larger range of ecosystems with different bacterial diversities.We have created a user-friendly database of bacterial functional traits, thanks to the properties of 19,455 bacterial strains. This database has been called BactoTraits. For example, oxygen preference, size and shape of bacteria, motility, optimum and range of pH and temperature, genome GC percent and trophic type are among the 19 traits included in BactoTraits. Based on the best-informed strains in the database, we identified five functional groups (i.e. mesophiles, competitors, colonizers, stress-sensitives and stress-tolerants) exhibiting a wide strain taxonomic diversity but with quite similar trait profile combinations.As an example of application, BactoTraits was used to characterize the traits and functional diversity of bacterial assemblages in soil samples from 10 sites with different physico-chemical properties and various levels of metal and polycyclic aromatic hydrocarbon (PAH) contaminations. Inference of functional traits was based on taxonomic diversity information obtained by high-throughput sequencing of 16S rDNA. This trait-based approach has allowed to discriminate soils according to their physico-chemical properties and levels of contamination and to go further into the description of the bacterial assemblages. Several bacterial traits were identified as indicators of specific contaminants such as metals (e.g. filament shape, microaerophile and temperature optimum/range higher than 40 °C) or PAHs (e.g. spherical shape, facultative anaerobe/aerobe, no spore production, pH optimum ≥ 8, low temperature optimum but high temperature variation tolerance).Inferring trait values from a taxonomy-based approach can be extended readily to other microbial systems and contexts such as (i) studies on soils and aquatic ecosystems, (ii) microbial ecology along various environmental gradients, (iii) human, plant and animal microbiotes, as well as (iv) trophic interactions between bacterial communities and their predators.

Integrated Phenotypic-Genotypic Analysis of Latilactobacillussakei from Different Niches.

Increasing attention has been paid to the potential probiotic effects of Latilactobacillus sakei. To explore the genetic diversity of L. sakei, 14 strains isolated from different niches (feces, fermented kimchi, and meat products) and 54 published strains were compared and analyzed. The results showed that the average genome size and GC content of L. sakei were 1.98 Mb and 41.22%, respectively. Its core genome mainly encodes translation and transcription, amino acid synthesis, glucose metabolism, and defense functions. L. sakei has open pan-genomic characteristics, and its pan-gene curve shows an upward trend. The genetic diversity of L. sakei is mainly reflected in carbohydrate utilization, antibiotic tolerance, and immune/competition-related factors, such as clustering regular interval short palindromic repeat sequence (CRISPR)–Cas. The CRISPR system is mainly IIA type, and a few are IIC types. This work provides a basis for the study of this species.

Genomic GC content drifts downward in most bacterial genomes.

In every kingdom of life, GC->AT transitions occur more frequently than any other type of mutation due to the spontaneous deamination of cytidine. In eukaryotic genomes, this slow loss of GC base pairs is counteracted by biased gene conversion which increases genomic GC content as part of the recombination process. However, this type of biased gene conversion has not been observed in bacterial genomes, so we hypothesized that GC->AT transitions cause a reduction of genomic GC content in prokaryotic genomes on an evolutionary time scale. To test this hypothesis, we used a phylogenetic approach to analyze triplets of closely related genomes representing a wide range of the bacterial kingdom. The resulting data indicate that genomic GC content is drifting downward in bacterial genomes where GC base pairs comprise 40% or more of the total genome. In contrast, genomes containing less than 40% GC base pairs have fewer opportunities for GC->AT transitions to occur so genomic GC content is relatively stable or actually increasing. It should be noted that this observed change in genomic GC content is the net change in shared parts of the genome and does not apply to parts of the genome that have been lost or acquired since the genomes being compared shared common ancestor. However, a more detailed analysis of two Caulobacter genomes revealed that the acquisition of mobile elements by the two genomes actually reduced the total genomic GC content as well.

ARAMIS: From systematic errors of NGS long reads to accurate assemblies.

NGS long-reads sequencing technologies (or third generation) such as Pacific BioSciences (PacBio) have revolutionized the sequencing field over the last decade improving multiple genomic applications like de novo genome assemblies. However, their error rate, mostly involving insertions and deletions (indels), is currently an important concern that requires special attention to be solved. Multiple algorithms are available to fix these sequencing errors using short reads (such as Illumina), although they require long processing times and some errors may persist.Here, we present Accurate long-Reads Assembly correction Method for Indel errorS (ARAMIS), the first NGS long-reads indels correction pipeline that combines several correction software in just one step using accurate short reads. As a proof OF concept, six organisms were selected based on their different GC content, size and genome complexity, and their PacBio-assembled genomes were corrected thoroughly by this pipeline. We found that the presence of systematic sequencing errors in long-reads PacBio sequences affecting homopolymeric regions, and that the type of indel error introduced during PacBio sequencing are related to the GC content of the organism. The lack of knowledge of this fact leads to the existence of numerous published studies where such errors have been found and should be resolved since they may contain incorrect biological information.ARAMIS yields better results with less computational resources needed than other correction tools and gives the possibility of detecting the nature of the found indel errors found and its distribution along the genome. The source code of ARAMIS is available at https://github.com/genomics-ngsCBMSO/ARAMIS.git

Parasphingorhabdus halotolerans sp. nov. isolated from marine sediment in Jeju Island.

A Gram-stain-negative, catalase- and oxidase-positive, rod-shaped bacterium, designated as JK6T was isolated from a coastal marine sediment in Jeju Island. Strain JK6T was characterized by polyphasic investigation including genome features. It grew at pH 5.0-9.0 (optimum 7.5), 18-30 °C (optimum 25 °C) and 1.0-7.0% (w/v) NaCl (optimum 2.0%). Strain JK6T utilized D-mannose, D-glucose, L-fucose, propionate and acetate as carbon and energy sources. The sole quinone was ubiquinone-10, and the major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, and sphingolipid. Strain JK6T was closely related to Parasphingorhabdus flavimaris SW-151T (98.2%), Parasphingorhabdus marina DSM 22363T (97.6%) and Parasphingorhabdus litoris FR1093T (97.6%) based on 16S rRNA gene sequence similarity. Genome length and GC content were 3.29 Mbp and 53.0%, respectively. Digital DNA-DNA relatedness, average nucleotide identity, and average amino acid identity between strain JK6T and P. flavimaris SW-151T were 16.6%, 73.9%, and 77.6%, respectively. These results showed that the strain can be recognized as a novel bacterium named Parasphingorhabdus halotolerans. The type strain of Parasphingorhabdus halotolerans sp. nov. is JK6T (= KCTC 72818T = VTCC 910111T).

Exploring the evolutionary characteristics between cultivated tea and its wild relatives using complete chloroplast genomes

BackgroundCultivated tea is one of the most important economic and ecological trees distributed worldwide. Cultivated tea suffer from long-term targeted selection of traits and overexploitation of habitats by human beings, which may have changed its genetic structure. The chloroplast is an organelle with a conserved cyclic genomic structure, and it can help us better understand the evolutionary relationship of Camellia plants.ResultsWe conducted comparative and evolutionary analyses on cultivated tea and wild tea, and we detected the evolutionary characteristics of cultivated tea. The chloroplast genome sizes of cultivated tea were slightly different, ranging from 157,025 to 157,100 bp. In addition, the cultivated species were more conserved than the wild species, in terms of the genome length, gene number, gene arrangement and GC content. However, comparing Camellia sinensis var. sinensis and Camellia sinensis var. assamica with their cultivars, the IR length variation was approximately 20 bp and 30 bp, respectively. The nucleotide diversity of 14 sequences in cultivated tea was higher than that in wild tea. Detailed analysis on the genomic variation and evolution of Camellia sinensis var. sinensis cultivars revealed 67 single nucleotide polymorphisms (SNPs), 46 insertions/deletions (indels), and 16 protein coding genes with nucleotide substitutions, while Camellia sinensis var. assamica cultivars revealed 4 indels. In cultivated tea, the most variable gene was ycf1. The largest number of nucleotide substitutions, five amino acids exhibited site-specific selection, and a 9 bp sequence insertion were found in the Camellia sinensis var. sinensis cultivars. In addition, phylogenetic relationship in the ycf1 tree suggested that the ycf1 gene has diverged in cultivated tea. Because C. sinensis var. sinensis and its cultivated species were not tightly clustered.ConclusionsThe cultivated species were more conserved than the wild species in terms of architecture and linear sequence order. The variation of the chloroplast genome in cultivated tea was mainly manifested in the nucleotide polymorphisms and sequence insertions. These results provided evidence regarding the influence of human activities on tea.

Occurrence and distribution of compound microsatellites in the genomes of three economically important virus families

Microsatellites are nonrandom hypervariable iterations of one to six nucleotides, existing across the coding as well as noncoding regions of virtually all known genomes, arising primarily due to polymerase slippage and unequal crossing over during replication events. Two or more perfect microsatellites located in close proximity form compound microsatellites. We studied the distribution of compound microsatellites in 118 ssDNA virus genomes belonging to three economically important virus families, namely Anelloviridae, Circoviridae, and Parvoviridae, known to predominantly infect livestock and humans. Among these virus families, 0-58.49% of perfect microsatellites were involved in the formation of compound microsatellites, the majority being located in the coding regions. No clear relationship existed between the genomic features (genome size and GC%) and compound microsatellite characteristics (relative abundance and relative density). The majority of the compound microsatellites resulted from di-SSR couples. A strong positive relationship was observed between the maximum distance value and length of compound microsatellite, percentage of microsatellites involved in the compound microsatellite formation, and relative microsatellite density. The degree of variability among microsatellite characteristics studied was largely a species-specific phenomenon. A major proportion of compound microsatellites was represented by similar motif combinations. The findings of the present study will help in better understanding of the structural, functional, and evolutionary role of compound microsatellites prevailing in the smaller genomes.

Assembly and comparative analysis of the complete mitochondrial genome of Suaeda glauca

BackgroundSuaeda glauca (S. glauca) is a halophyte widely distributed in saline and sandy beaches, with strong saline-alkali tolerance. It is also admired as a landscape plant with high development prospects and scientific research value. The S. glauca chloroplast (cp) genome has recently been reported; however, the mitochondria (mt) genome is still unexplored.ResultsThe mt genome of S. glauca were assembled based on the reads from Pacbio and Illumina sequencing platforms. The circular mt genome of S. glauca has a length of 474,330 bp. The base composition of the S. glauca mt genome showed A (28.00%), T (27.93%), C (21.62%), and G (22.45%). S. glauca mt genome contains 61 genes, including 27 protein-coding genes, 29 tRNA genes, and 5 rRNA genes. The sequence repeats, RNA editing, and gene migration from cp to mt were observed in S. glauca mt genome. Phylogenetic analysis based on the mt genomes of S. glauca and other 28 taxa reflects an exact evolutionary and taxonomic status of S. glauca. Furthermore, the investigation on mt genome characteristics, including genome size, GC contents, genome organization, and gene repeats of S. gulaca genome, was investigated compared to other land plants, indicating the variation of the mt genome in plants. However, the subsequently Ka/Ks analysis revealed that most of the protein-coding genes in mt genome had undergone negative selections, reflecting the importance of those genes in the mt genomes.ConclusionsIn this study, we reported the mt genome assembly and annotation of a halophytic model plant S. glauca. The subsequent analysis provided us a comprehensive understanding of the S. glauca mt genome, which might facilitate the research on the salt-tolerant plant species.

The complete chloroplast genome of Stauntonia chinensis and compared analysis revealed adaptive evolution of subfamily Lardizabaloideae species in China

BackgroundStauntonia chinensis DC. belongs to subfamily Lardizabaloideae, which is widely grown throughout southern China. It has been used as a traditional herbal medicinal plant, which could synthesize a number of triterpenoid saponins with anticancer and anti-inflammatory activities. However, the wild resources of this species and its relatives were threatened by over-exploitation before the genetic diversity and evolutionary analysis were uncovered. Thus, the complete chloroplast genome sequences of Stauntonia chinensis and comparative analysis of chloroplast genomes of Lardizabaloideae species are necessary and crucial to understand the plastome evolution of this subfamily.ResultsA series of analyses including genome structure, GC content, repeat structure, SSR component, nucleotide diversity and codon usage were performed by comparing chloroplast genomes of Stauntonia chinensis and its relatives. Although the chloroplast genomes of eight Lardizabaloideae plants were evolutionary conserved, the comparative analysis also showed several variation hotspots, which were considered as highly variable regions. Additionally, pairwise Ka/Ks analysis showed that most of the chloroplast genes of Lardizabaloideae species underwent purifying selection, whereas 25 chloroplast protein coding genes were identified with positive selection in this subfamily species by using branch-site model. Bayesian and ML phylogeny on CCG (complete chloroplast genome) and CDs (coding DNA sequences) produced a well-resolved phylogeny of Lardizabaloideae plastid lineages.ConclusionsThis study enhanced the understanding of the evolution of Lardizabaloideae and its relatives. All the obtained genetic resources will facilitate future studies in DNA barcode, species discrimination, the intraspecific and interspecific variability and the phylogenetic relationships of subfamily Lardizabaloideae.

A database of sequenced genomes of different Streptomyces albus J1074 strains and uses thereof

Streptomyces albus J1074 has recently emerged as a powerful chassis strain for natural product research and discovery, as well as model to investigate various aspects of actinobacterial biology. A number of genetic tools have been developed to facilitate the use of this strain for the aforementioned purposes. One of the promising approaches is to introduce into J1074 genome mutations that would improve the antibiotic-producing capacity of J1074. Particularly, we reported a collection of spontaneous and genomically engineered J1074 mutants carrying mutation in genes for ribosomal protein S12, RNA polymerase beta subunit etc. We took advantage of this collection to build an in-house database which would host (both current and future) the primary and curated sequencing data for these mutants. The database is available at https://biotools.online/media/. The main benefits of the database lie in the known pedigree of the strains, which allows deep interpretation of the data. For example, there is lively – and unresolved – debate on the origins and consequences of the GC composition in actinobacteria. A better understanding of this issue should improve our knowledge of genome evolution in bacteria and will have a number of biotechnological ramifications. We used our Streptomyces albus J1074 dataset as an experimental model to reveal genome-wide spectrum of mutation, which appears to be biased towards elevated GC content. We also included the high-quality genomes of the other streptomycetes into our databse for comparative purposes. The genomic GC content in streptomycetes varies from 75 % to 66.5 %, with median value being 72 %. The GC content of secondary metabolic genes of S. coelicolor is less variable than that of primary metabolic genes, an indicative of different selection pressure on these gene groups. Along with selective constraints, the peculiarities of Streptomyces DNA mismatch repair might contribute to the skewed GC content of their genomes. Further uses of the database may include the development of a more precise knowledge of the mutation rate as well as population genetic processes within this species and genus.

High genetic diversity in Campylobacter concisus isolates from patients with microscopic colitis

The emerging intestinal pathogen Campylobacter concisus has been associated with prolonged diarrhoea and classic inflammatory bowel diseases (IBD) and was recently also linked with microscopic colitis (MC). Previous reports have observed a high genetic diversity within isolates from diarrhoeic and IBD patients and from healthy controls (HC), and division of isolates into two major genomospecies (GS1 and GS2). The aim of this study was to describe genetic diversity in 80 recently cultivated MC biopsy and faecal isolates of C. concisus by multi-locus sequence typing (MLST); and to compare the phylogenetic relatedness to 102 isolates from diarrhoeic and IBD patients and HCs by k-mer-based distance estimation. MLST revealed high genetic diversity in MC isolates with 72 novel sequence types. K-mer divided MC isolates into two distinct clusters (cluster 1 n = 21, cluster 2 n = 49), with a significantly higher prevalence of cluster 2 isolates in biopsies than in faeces, p = 0.009. K-mer divided the 182 isolates into two major phylogenetic clusters: cluster 1 (GS1 isolates) and cluster 2 (GS2 isolates), which further differentiated into three subgroups. Cluster 1 and the three cluster 2 subgroups were each distinctive in mean genome size and GC count. Isolates from all disease phenotypes were present in cluster 1 and cluster 2 subgroup 2 and 3, whereas cluster 2 subgroup 1 only contained isolates restricted to patients with ulcerative colitis (n = 10) and HC (n = 4).

Genome survey sequencing and genetic diversity of cultivated Akebia trifoliata assessed via phenotypes and SSR markers.

Akebia trifoliata (Lardizabalaceae) is an important medicinal plant with multiple pharmacological effects. However, the lack of genomic information had limited the further excavation and utilization of this plant. An initial survey of the genome A. trifoliata was performed by next-generation sequencing, and then the genome size was inferred by flow cytometry. The whole genome survey of A. trifoliata generated 61.90Gb of sequence data with approximately 95.51 × coverage. The genome size, heterozygosity and GC content obtained by k-mer analysis were almost 648.07Mb, 0.72% and 36.11%, respectively. The genome size calculated by flow cytometry was 685.77Mb, which was consistent with the results of genome survey. A total of 851,957 simple sequence repeats (SSR) were identified in the A. trifoliata genome. Twenty-eight phenotypic traits and thirty pairs of SSR primers were selected for the analysis of the genetic diversity of 43 accessions of cultivated A. trifoliata. The results showed that 216 bands were generated by 30 pairs of SSR primers, of which 189 (87.5%) were polymorphic. In addition, the phenotypes and SSR markers were used for cluster analysis of 43 cultivated accessions. The results of the two clustering methods were partially consistent. The genome survey of A. trifoliata demonstrated that the genome size of this plant was about 648.07Mb. In the present study, the size and characteristics of the genome of A. trifoliata were reported for the first time, which greatly enriched the genomic resources of A. trifoliata for the further research and utilization.

Prediction of Monophyletic Groups Based on Gene Order and Sequence Similarity in Organelle DNA

Organelle genomics has become its own field of study. Much information can be gleaned from the study of cell organelles. The differences in the genomes of organelles, such as the mitochondrion and the chloroplast are amenable to phylogenetic and cladistic studies. These differences include the genome sequence, GC%, genome length and gene order. The conserved nature of the organelle genomes and the gene inventory of both mitochondrial and chloroplast genomes also make this easier to accomplish. This paper includes a review of existing organelle genome software. These include gene annotation and genome visualization tools as well as organelle gene databases for both mitochondrion and plastid. A new R tool, available on github, called “Organelle DNA Lineages”, or ODL, was written to compare and classify organelle genomes based on their genome sequence and gene order. The software was run on the mitochondrial genomes of a set of 51 cephalopod species, delineating ten separate monophyletic groups, including argonauts, nautiluses, octopuses, cuttlefish, and six squid groups. This new tool can help enrich and expand the field of organelle genomics.

ChIAMM: A Mixture Model for Statistical Analysis of Long-Range Chromatin Interactions From ChIA-PET Experiments.

Chromatin interaction analysis by paired-end tag sequencing (ChIA-PET) is an important experimental method for detecting specific protein-mediated chromatin loops genome-wide at high resolution. Here, we proposed a new statistical approach with a mixture model, chromatin interaction analysis using mixture model (ChIAMM), to detect significant chromatin interactions from ChIA-PET data. The statistical model is cast into a Bayesian framework to consider more systematic biases: the genomic distance, local enrichment, mappability, and GC content. Using different ChIA-PET datasets, we evaluated the performance of ChIAMM and compared it with the existing methods, including ChIA-PET Tool, ChiaSig, Mango, ChIA-PET2, and ChIAPoP. The result showed that the new approach performed better than most top existing methods in detecting significant chromatin interactions in ChIA-PET experiments.

Enhanced nucleotide analysis enables the quantification of deoxynucleotides in plants and algae revealing connections between nucleoside and deoxynucleoside metabolism.

Detecting and quantifying low-abundance (deoxy)ribonucleotides and (deoxy)ribonucleosides in plants remains difficult; this is a major roadblock for the investigation of plant nucleotide (NT) metabolism. Here, we present a method that overcomes this limitation, allowing the detection of all deoxy- and ribonucleotides as well as the corresponding nucleosides from the same plant sample. The method is characterized by high sensitivity and robustness enabling the reproducible detection and absolute quantification of these metabolites even if they are of low abundance. Employing the new method, we analyzed Arabidopsis thaliana null mutants of CYTIDINE DEAMINASE, GUANOSINE DEAMINASE, and NUCLEOSIDE HYDROLASE 1, demonstrating that the deoxyribonucleotide (dNT) metabolism is intricately interwoven with the catabolism of ribonucleosides (rNs). In addition, we discovered a function of rN catabolic enzymes in the degradation of deoxyribonucleosides in vivo. We also determined the concentrations of dNTs in several mono- and dicotyledonous plants, a bryophyte, and three algae, revealing a correlation of GC to AT dNT ratios with genomic GC contents. This suggests a link between the genome and the metabolome previously discussed but not experimentally addressed. Together, these findings demonstrate the potential of this new method to provide insight into plant NT metabolism.

Sphingomonas changnyeongensis sp. nov. isolated from the Hapcheon-Changnyeong barrage area in the Nakdong river.

The novel bacterial strain C33T was isolated from a freshwater sample collected from the Hapcheon-Changnyeong barrage. The Gram-negative, motile, yellow-pigmented strain C33T was characterized as a rod-shaped and strictly aerobic bacterium. A 16S-rRNA phylogenetic analysis revealed that this strain was most closely related to Sphingomonas changbaiensis V2M44T, Sphingomonas tabacisoli X1-8T, and Sphingomonas flavalba ZLT-5T with 97.1, 97.0, and 95.0 % 16S-rRNA sequence similarities, respectively. The genomic DNA GC content of strain C33T was estimated at 65.0 mol%. The average nucleotide identity of strain C33T relative to S. changbaiensis V2M44T and S. flavalba ZLT-5T was found to be 77.0 and 75.6%, with average amino-acid identities of 69.9, and 66.7%, and the digital DNA-DNA hybridization values of 21.3 and 17.7 %, respectively. The cells grew at 19-37 °C and pH 6-9 with 0-0.5 % (w/v) NaCl (optimum: 28 °C, pH 6.5, and 0 % NaCl). The major component identified in the polyamine pattern was sym-homospermidine, and the main ubiquinone was Q-10. The predominant polar lipids characterized were diphophatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidyldimethylethanolamine, and sphingoglycolipid. Iso-C15 : 0, C15 : 0 anteiso, and summed feature 3 (C16 : 1 ω6c and/or C16 : 1 ω7c) were found to be the primary cellular fatty acids in strain C33T. Based on these genotypic and phenotypic characteristics, strain C33T was classified as a novel species of the genus Sphingomonas; and the name Sphingomonas changnyeongensis sp. nov. is proposed (=KACC 21511T=JCM 33880T).

The complete chloroplast genome of Gleditsia sinensis and Gleditsia japonica: genome organization, comparative analysis, and development of taxon specific DNA mini-barcodes

Chloroplast genomes have been widely considered an informative and valuable resource for molecular marker development and phylogenetic reconstruction in plant species. This study evaluated the complete chloroplast genomes of the traditional Chinese medicine Gleditsia sinensis and G. japonica, an adulterant of the former. The complete chloroplast genomes of G. sinensis and G. japonica were found to be of sizes 163,175 bp and 162,391 bp, respectively. A total of 111 genes were identified in each chloroplast genome, including 77 coding sequences, 30 tRNA, and 4 rRNA genes. Comparative analysis demonstrated that the chloroplast genomes of these two species were highly conserved in genome size, GC contents, and gene organization. Additionally, nucleotide diversity analysis of the two chloroplast genomes revealed that the two short regions of ycf1b were highly diverse, and could be treated as mini-barcode candidate regions. The mini-barcode of primers ZJ818F-1038R was proven to precisely discriminate between these two species and reflect their biomass ratio accurately. Overall, the findings of our study will shed light on the genetic evolution and guide species identification of G. sinensis and G. japonica.